Ebook Noninvasive mechanical ventilation and difficult weaning in critical care: Part 2

(BQ) Part 2 book Noninvasive mechanical ventilation and difficult weaning in critical care has contents: Post extubation failure and use of non invasive mechanical ventilation, non invasive mechanical ventilation and decannulation in tracheostomized patients, discharge ventilator depend patients,... and other contents.

© Springer International Publishing Switzerland 2016

A.M Esquinas (ed.), Noninvasive Mechanical Ventilation and Diffi cult Weaning

in Critical Care: Key Topics and Practical Approaches,

DOI 10.1007/978-3-319-04259-6_27

A Hernandez Voth , MD ( * ) • P Benavides Mañas , MD • J Sayas Catalan , MD

Pulmonology Service , Hospital Universitario 12 de Octubre , Madrid , Spain

e-mail: anahvoth@gmail.com ; pedrobenavides79@yahoo.es ; jsayascat@gmail.com

27

Use of Noninvasive Mechanical

Ventilation in Lung Transplantation

Ana Hernandez Voth , Pedro Benavides Mañas ,

and Javier Sayas Catalán

Abbreviations

CF Cystic fi brosis

COPD Chronic obstructive pulmonary disease

CPAP Continuous positive airway pressure

ETI Endotracheal intubation

FEV1 Flow expiratory volume in the fi rst second

ICU Intensive care unit

ILD Interstitial lung disease

is one of the ventilatory support techniques that has achieved greater use in recent years, becoming available at most hospitals and being successfully implemented in intensive care units (ICUs), intermediate care units, and recovery units In this chap-ter, the role of NIV in the management of lung transplant patients in the pretransplant period, in the early postoperative period, and with LT complications, or to carry out diagnostic and therapeutic techniques in transplant patients, is reviewed

27.2 Discussion and Analysis

27.2.1 NIV in LT Indication Diseases

Many candidates for LT have a chronic domiciliary NIV indication as part of their underlying lung disease treatment There is evidence of NIV benefi t as a bridge to

LT in two obstructive pathologies: COPD and cystic fi brosis (CF)

COPD exacerbation is a situation where the use of NIV has a higher degree of evidence, particularly in severe exacerbations that develop respiratory acidosis These exacerbations are frequent in patients with COPD on the waiting list for LT, and NIV can decrease mortality in up to 50 % cases of COPD exacerbation with respiratory acidosis when compared with standard treatment [ 1 ] This impact on sur-vival is much higher than that obtained from any of pharmacological treatments used

in COPD exacerbations, and it has a high degree of evidence to be recommended NIV usefulness in stable COPD is more controversial In patients with chronic hypercapnic respiratory failure, several studies with contradictory results have been published Some of them show a slight increase in survival of patients with COPD with hypercapnic respiratory insuffi ciency, whereas others have not found any dif-ferences in terms of exacerbations or survival Nevertheless, although there is no conclusive scientifi c evidence about its usefulness in stable COPD, it is one of the main indications of chronic domiciliary NIV in Europe

Regarding the use of NIV in COPD as bridge to LT, an improvement in a nary function parameter (an increase of 0.20 ± 0.18 l (liters) in FEV1) has been described, along with a small increase in survival while on the waiting list for LT [ 2 ] However, these are limited data because of the absence of a control group and the presence of important selection bias in their results Functional improvement has been achieved in very severe COPD by using NIV prior to an oncologic thoracic surgery, which can be extrapolated to very severe COPD patients on the waiting list for LT

NIV in CF patients has shown short-term improvement in oxygen saturation and in pCO 2 levels, as well as a decrease in the work of breathing, alveolar ventilation and exercise tolerance improvement, and pulmonary function stabilization during reha-bilitation [ 3 , 4 ] When these patients have a severe exacerbation that requires ventila-tory support, invasive mechanical ventilation has a bad prognosis associated with infectious complications from frequent bronchial colonization, as ventilator- associated pneumonia As a bridge to LT, NIV in CF can reduce mortality from this cause

27.2.2 NIV in the LT Early Postoperative Period

Generally, after thoracic surgery there are strong effects on respiratory function that relate to postoperative prolonged mechanical ventilation requirements In the par-ticular case of LT, there are also other associated factors: the usual myopathy that terminal respiratory insuffi ciency patients present, functional alterations due to clamshell incision in bilateral LT, and postoperative diaphragm involvement due to phrenic nerve damage

A Hernandez Voth et al

NIV use has been considered in the LT early postoperative period with three major objectives: to facilitate early extubation, to prevent reintubation due to post- surgery ventilatory failure, and to treat ventilatory failure once it is established [ 5 ]

27.2.2.1 NIV as a Tool in Early Extubation

Early extubation is of particular interest in immunosuppressed patients to avoid infectious consequences of prolonged mechanical ventilation, but also to avoid air-way complications Prolonged mechanical ventilation can lead to barotrauma on the sutures associated with air leakage, modifying pulmonary defense mechanisms and leading to bronchial anastomosis infection

Consequences of reintubation due to postsurgical ventilatory failure may result

in a remarkable increase of mortality

Hypoxemia, hypercapnia and muscle fatigue due to an increase in breathing work are the most common causes of failed extubation Furthermore, at the time

of extubation, there is a loss of the intrathoracic positive pressure maintained so far This induces hemodynamic changes, increasing venous return to the right ventricle, left cardiac septum displacement, and a possible increase in pulmonary artery pressure and pulmonary capillary wedge pressure All these events can result in the development of interstitial pulmonary edema and in a higher expira-tory work Pressure support associated with some degree of positive end-expira-tory pressure can offset these effects, even applying ventilation in the noninvasive mode

NIV can represent a helpful tool in extubation of patients who do not succeed a T-tube trial Thus, early weaning protocols have been developed in LT including epidural analgesia, early seating position, intensive physiotherapy, and NIV [ 6 ]

In our experience, we have reviewed retrospectively NIV use in the early operative period of 54 lung transplant patients for three consecutive years Post- extubation NIV was indicated in case of high levels of pCO 2 during a T-piece trial

post-or after extubation, ventilatpost-ory mechanisms alterations, post-or moderate respiratpost-ory acidosis A major indication for LT was COPD (48 %), and the other indications were interstitial lung disease (ILD) (26 %), pulmonary arterial hypertension (11 %), CF (7 %), and others (6 %) Three patients had chronic domiciliary NIV as

a bridge to LT (two had COPD, the other one had ILD) Fourteen patients (26 %) constituted a NIV group having fi ve endotracheal reintubations (three of them ended in tracheostomy), whereas in the non-NIV group there were three endotra-cheal reintubations (all of them ended in tracheostomy) There were no complica-tions observed in the NIV group related to NIV, as well as fewer hours of endotracheal intubation (ETI) and shorter length of stay in the ICU compared with non-NIV group (Table 27.1 )

In our study, NIV was a useful tool in the LT early postoperative period, and it was associated with absence of airway complications, less ETI time, and shorter length of stay on the ICU

Another circumstance that frequently motivates a prolonged time spent on sive mechanical ventilation and prolonged ICU length of stay is postsurgical phrenic paralysis In these cases, NIV use can reduce time spent on invasive mechanical ventilation and, hence, length of stay on the ICU

inva-27 Use of Noninvasive Mechanical Ventilation in Lung Transplantation

27.2.2.2 NIV as Prevention of Post-extubation Ventilatory Failure

Reintubation due to ventilatory failure is associated with high mortality, mainly because of its association with infectious events, which increases prophylactic use

of NIV in patients at risk of reintubation We do not provide concrete evidence in

LT, but there are several studies on intubated patients at risk of post-extubation tilatory failure in comparable circumstances to lung transplant patients’ conditions that have shown a decrease in post-extubation ventilatory failure rate in patients using NIV after extubation, trying to maintain NIV as long as possible in the fi rst

ven-24 h, compared with patients who received standard treatment [ 7 ]

Along with this, early use of NIV could be considered in lung transplant patients who do not pass a T-piece trial or have hypercapnia during this trial, looking for a protective effect on further development of ventilatory failure

27.2.2.3 NIV as a Treatment of Ventilatory Failure

In post-extubation ventilatory failure, the use of NIV seems attractive as a way to avoid the need for reintubation However, in this case, there are dissenting opinions about its safety and usefulness Once ventilatory failure is established, NIV may not

be as useful as we think; it can even have a deleterious effect on survival because it may delay a needed intubation, increasing the overall mortality However, in some studies performed in ventilatory failure in the postoperative period in thoracic sur-gery, NIV allowed a reduction in the rate of respiratory complications and its associ-ated mortality in a relevant way

27.2.3 NIV in LT Complications That Present Ventilatory Failure

A major cause of readmission to the ICU in the late postoperative period of LT is respiratory failure This might be due to many circumstances, most commonly infection, cardiogenic acute pulmonary edema, drug side effects, and acute rejec-tion These situations with higher ventilatory requirements are often worsened by different circumstances related to LT: myopathy due to steroid use and ventilatory mechanics alterations due to surgery Thus, it is known that lung transplant patients who require invasive mechanical ventilation have a worse prognosis than patients admitted to the ICU due to diseases not derived from surgery [ 8 ]

Table 27.1 Variables analyzed in the early postoperative period in lung transplant patients

Hospital Universitario 12 de Octubre

NIV noninvasive mechanical ventilation, ICU intensive care unit, PCO 2 carbon dioxide partial pressure in blood

A Hernandez Voth et al

Moreover, NIV has demonstrated its usefulness in treating patients with emic respiratory failure of different etiologies, reducing the need for ETI and thereby decreasing infectious complications from it (nosocomial pneumonia and septic shock) and decreasing global mortality [ 9 ]

Along with the evidence that NIV is safe and may be benefi cial in hypoxemic failure, this technique also has utility in ventilatory failure management in immuno-suppressed patients In these patients, when ventilatory failure requires ETI, mortal-ity increases signifi cantly, but NIV use enables to reduce reintubation rate and mortality, compared with reintubated patients Particularly in lung transplant patients it has demonstrated an improvement in physiological parameters (arterial blood gases analysis, breathing rate, etc.) after introducing NIV as acute respiratory failure treatment However, these results derive from a descriptive study without a control group, so we can only conclude that the NIV option is safe and may be ben-efi cial to these patients [ 10 ]

27.2.4 NIV in Diagnostic and Therapeutic Techniques in Lung

Transplant Patients

Frequently, lung transplant patients require performance of diagnostic or tic techniques in the airway, particularly bronchoscopy Bronchoscopy can reduce tracheal lumen in 10–15 % of patients and increases work of breathing, generating

therapeu-a relevtherapeu-ant hypoxemitherapeu-a Procedures like bronchotherapeu-alveoltherapeu-ar ltherapeu-avtherapeu-age ctherapeu-an ctherapeu-ause therapeu-a gretherapeu-ater decline of oxygenation, and aspiration of bronchial secretions during bronchos-copy performance may produce a pressure drop at the end of expiration that facili-tates alveolar collapse Frequently, these techniques should be performed in patients with severe hypoxemia, making it necessary to assure adequate oxygen-ation NIV use can allow the performance of these procedures, avoiding the need for intubation and invasive ventilation Bronchoscopy performance has been described under continuous positive airway pressure (CPAP), a particularly useful nonmechanical CPAP system designed by Boussignac, or the “helmet,” but there are no randomized studies that compare bronchoscopy performance under NIV versus ETI In general, it is described that NIV can signifi cantly improve oxygen-ation during bronchoscopy performance in patients with refractory hypoxemia compared with conventional oxygen therapy Nevertheless, it may present some disadvantages, particularly in hemodynamically unstable patients, severely aci-dotic patients (pH < 7.20), or patients with no possibility of airway isolation with bronchoaspiration or gastric distension as associated complications

Conclusion

NIV is a useful tool in lung transplant patients, where avoiding intubation is cial It can also improve work of breathing, gas exchange, oxygenation, and exer-cise tolerance Its applications include all the range of complications that may be present in the pretransplant and post-transplant period (early and late ones)

cru-27 Use of Noninvasive Mechanical Ventilation in Lung Transplantation

In addition, NIV presents obvious advantages over invasive mechanical tilation, especially related to the lack of infectious complications associated with the latter It also allows patient feeding, talking, and expectorating, can be used intermittently, and its withdrawal or its restart is easy However, its use is not free

ven-of risk, as with the delay ven-of a necessary intubation, and may have implications in prognosis, which is why it is recommended that it be used under close surveil-lance and with skilled staff trained in its application

References

1 Rabe KF, et al Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: GOLD executive summary Am J Respir Crit Care Med 2007;176(6):532–55

2 Wiebel M, et al Noninvasive self-ventilation–successful transition aid in the waiting period before lung transplantation? Med Klin (Munich) 1995;90(1 Suppl 1):32–4

3 Fauroux B, et al Long-term noninvasive ventilation in patients with cystic fi brosis Respiration 2008;76(2):168–74

4 Serra A, et al Non-invasive proportional assist and pressure support ventilation in patients with cystic fi brosis and chronic respiratory failure Thorax 2002;57(1):50–4

5 Feltracco P, et al Noninvasive ventilation in postoperative care of lung transplant recipients Transplant Proc 2009;41(4):1339–44

Key Major Recommendations

• NIV use in diseases that may require LT is clear Numerous candidates for

LT have an indication of chronic domiciliary NIV as part of the underlying disease treatment There is evidence of NIV’s benefi t as a transition aid to

LT in two obstructive pathologies: COPD and CF

• NIV use in the early postoperative period after LT has three major tives: to facilitate early extubation, to prevent reintubation due to post- surgery ventilatory failure, and to treat ventilatory failure once it is established In our experience, NIV can decrease the number of reintuba-tions and length of stay in the ICU compared with patients in whom NIV has not been used during their stay on the ICU

objec-• NIV is safe and may be benefi cial in hypoxemic failure It is very useful in ventilatory failure management of immunosuppressed patients Particularly

in lung transplant patients, an improvement of physiological parameters (arterial blood gases, breathing rate, etc.) has been observed after introduc-tion of NIV as acute respiratory failure treatment in the late postoperative period

• NIV can signifi cantly improve oxygenation during diagnostic and peutic procedures in lung transplant patients, including bronchoscopy per-formance in patients with refractory hypoxemia to isolated oxygen therapy

thera-A Hernandez Voth et al

© Springer International Publishing Switzerland 2016

A.M Esquinas (ed.), Noninvasive Mechanical Ventilation and Diffi cult Weaning

in Critical Care: Key Topics and Practical Approaches,

DOI 10.1007/978-3-319-04259-6_28

E F Akcil , MD ( * ) • O K Dilmen , MD • Y Tunali , MD

Department of Anaesthesiology and Intensive Care Medicine , Istanbul University Cerrahpasa

School of Medicine , Istanbul , Turkey

e-mail: erenfat@yahoo.com ; ozlemkorkmaz1978@mynet.com ; ytunali@yahoo.com

28

Noninvasive Mechanical Ventilation

in Postoperative Spinal Surgery

Eren Fatma Akcil , Ozlem Korkmaz Dilmen ,

and Yusuf Tunali

28.1 Introduction

Noninvasive mechanical ventilation (NIMV) is widely used in the treatment of acute respiratory failure (ARF), and it is particularly effective in the treatment of acute exac-erbation of chronic obstructive pulmonary disease (COPD) and cardiogenic pulmo-nary edema [ 1 ] Acute postoperative respiratory failure is another of the application areas of NIMV [ 2 ] Postoperative pulmonary complications (PPCs) are critical in the postoperative period because they increase hospital length of stay (LOS), morbidity, and mortality [ 2 , 3 ] Atelectasis, pneumonia, bronchospasm, pleural effusion, pulmo-nary edema, pulmonary embolism, and pneumothorax are the clinical forms of PPC that occur most often Many cases of postoperative ARF are short and can be treated successfully with supplemental oxygen, reversal of neuromuscular blocking agents, bronchodilators, deep-breathing exercises, and chest physiotherapy if no intubation or mechanical ventilation is required Postoperative reintubation and invasive mechani-cal ventilation themselves are also suggested as relating to PPCs Therefore, because

it is a noninvasive method, NIMV can be properly used in postoperative ARF [ 4 ]

28.2 Discussion

The effi cacy of NIMV has been demonstrated in postoperative ARF, including diac, thoracic, thoracoabdominal, and abdominal surgery [ 1 – 5 ] Various complica-tions may develop following spinal surgery; the most common are cardiac

complications (3 %), pulmonary complications (1.2 %), and pneumonia (1.2 %) Postoperative complications were reported to increase mortality; advanced age (>65), comorbidities, and complexity of surgical interventions are contributing factors [ 6 , 7 ]

It is obvious that scoliosis, trauma, and oncological spinal surgical interventions are more invasive interventions than degenerative disc disease surgery, with higher peri-operative morbidity and mortality rates Moreover, in posterior lumbar fusion opera-tions, mortality is lower than with anterior and thoracic approaches [ 6 ] It has been demonstrated that diabetes mellitus (particularly insulin-dependent), obesity, COPD, and steroid use increase complications in lumbar stenosis surgery [ 7 ] Thoracic disk surgery is particularly associated with pulmonary complications (6.9 %) [ 8 ] In those undergoing anterior/anterolateral decompression and fusion, all complications and pulmonary complications were reported to be greater than in those undergoing poste-rior/posterolateral decompression and only disc decompression with fusion

Although we report high mortality and morbidity rates in scoliosis surgery, cal interventions are needed to improve the quality of life of these patients and for the correction of the vital functions Irreversibly affected respiratory and cardiac functions may complicate both anesthesia and surgery Spinal deformity progres-sion may cause deteriorated respiratory functions Secondary scoliosis may develop

surgi-in children with muscular dystrophies and myopathies, and, hence, spsurgi-inal fusion surgery is required There is alveolar hypoventilation and hypercapnia susceptibility due to respiratory muscle weakness, and inability to cough in scoliosis accompa-nied by neuromuscular diseases

Postoperative pulmonary function is seen to deteriorate further than preoperative function In a case series including eight patients, early pre- and postoperative NIMV applications are effective in protecting the respiratory functions in these chil-dren with restrictive respiratory failure [ 9 ] Pre- and postoperative biphasic positive airway pressure was performed in children with forced vital capacity (FVC) ≤ 1 L, those undergoing scoliosis surgery, and in a case of desaturation due to hypoventila-tion during the night, and no difference between preoperative and postoperative respiratory functions was observed [ 9 ] When NIMV is used in chronic respiratory failure due to scoliosis, it may improve arterial oxygenation, increase the quality of life, and reduce the hospital LOS Following scoliosis surgery, acute respiratory failure may develop, particularly in patients with poor respiratory functions in the preoperative period Atelectasis, depressant effects of opioids, and pain are the con-tributing factors to the risk of postoperative respiratory failure in these patients [ 10 ]

It is established that the application of mechanically assisted cough and nasal mittent positive pressure ventilation before and after surgery ensures that extubation will performed successfully and invasive mechanical ventilation will not be required

inter-in patients undergointer-ing scoliosis surgery with FVC values of < 40 % before the gery [ 11 ] In a study of 73 patients undergoing scoliosis surgery, NIMV was applied

sur-in 28 patients sur-in the perioperative period, and PPC developed less often sur-in this group than in those who did not undergo NIMV [ 12 ]

In the pulmonary function tests of the children with muscular dystrophy, ing that the vital capacity decreases by 3–10 % per year and surgery is contraindi-cated without opening tracheostomy in cases with FVC values of below 40 %, perioperative NIMV application and early surgery seem to be advantageous [ 13 ]

assum-E.F Akcil et al.

Respiratory function tests guide us in determining the need of ventilator tively and PPC progression in these patients The use of short-acting anesthetic drugs, methods reducing blood loss, and effective pain control may reduce postop-erative ventilator requirements [ 14 ]

3 Chiumello D, Chevallard G, Gregoretti C Non-invasive ventilation in postoperative patients:

a systematic review Intensive Care Med 2011;37:918–29

4 Jaber S, Chanques G, Jung B Postoperative noninvasive ventilation Anesthesiology 2010;112:453–61

5 Albala MZ, Ferrignio M Short term noninvasive ventilation in the postanesthesia care unit: a case series J Clin Anesth 2005;17:636–9

6 Pumberger M, Chiu YL, Ma Y, et al Perioperative mortality after lumbar spinal fusion gery: an analysis of epidemiology and risk factors Eur Spine J 2012;21:1633–9

7 Deyo RA, Hickam D, Duckard JP, et al Complications after surgery for lumbar stenosis in a veteran population Spine 2013;38:1695–702

8 Jain A, Menga EN, Hassanzadeh H, et al Thoracic disc disorders with myelopathy Spine 2014;39:1233–8

9 Gill I, Eagle M, Mehta JS, et al Correction of neuromuscular scoliosis in patients with isting respiratory failure Spine 2006;31:2478–83

10 Doherty MJ, Millner PA, Latham M, et al Non-invasive ventilation in the treatment of tory failure following corrective spinal surgery Anaesthesia 2001;56:235–47

11 Bach JR, Sabharwal S High pulmonary risk scoliosis surgery: role of noninvasive ventilation and related techniques J Spinal Disord Tech 2005;18:527–30

12 Chong HS, Padua MRA, Kim JS, et al Usefulness of noninvasive positive-pressure ventilation during surgery of fl accid neuromuscular scoliosis J Spinal Disord Tech 2015 doi: 10.1097 BSD.0000000000000234

13 Mills B, Bach JR, Zhao C, et al Posterior spinal fusion in children with fl accid neuromuscular scoliosis: the role of noninvasive positive pressure ventilatory support J Pediatr Orthop 2013;33:488–93

14 Almenrader N, Patel D Spinal fusion surgery in children with non-idiopathic scoliosis: is there

a need for routine postoperative ventilation? Br J Anaesth 2006;97(6):851–7

Key Recommendations

• Respiratory function tests should be evaluated in the preoperative period of thoracic spinal and scoliosis surgery

• Short-acting anesthetic drugs should be preferred

• Postoperative pain management is essential for recovery

28 Noninvasive Mechanical Ventilation in Postoperative Spinal Surgery

© Springer International Publishing Switzerland 2016

A.M Esquinas (ed.), Noninvasive Mechanical Ventilation and Diffi cult Weaning

in Critical Care: Key Topics and Practical Approaches,

NIV Noninvasive ventilation

NPPV Noninvasive positive-pressure ventilation

PF PaO 2 /FiO 2 ratio

PPC Postoperative pulmonary complications

PRF Postoperative respiratory failure

RCT Randomized controlled trial

29.1 Introduction

Patients undergoing abdominal surgery are at risk of developing postoperative respiratory failure (PRF) and postoperative pulmonary complications (PPCs), including hypoxemia, atelectasis, bronchospasm, pleural effusions, aspiration

A J Morgan , BSc, MRCP(Ed), FRCA, FFICM • A J Glossop , MRCP, FRCA, DICM,

FFICM ( * )

Department of Critical Care , Sheffi eld Teaching Hospitals NHS Foundation Trust ,

Herries Road , Sheffi eld S5 7AU , UK

e-mail: alastair.glossop@sth.nhs.uk

29

Authors’ Disclosures Alastair Glossop has previously received a scholarship awarded by the

National Institute for Health and Clinical Excellence (NICE) but received no fi nancial incentive

pneumonitis, sputum plugging, lobar collapse, pneumonia, and the requirement for mechanical ventilation (MV) The incidences of PRF and PPCs are 0.2–3.4 and 7.2–40 %, respectively, following elective abdominal surgery, with even higher rates following emergency surgery and in patients older than 80 years [ 1 ] Depending

on patient characteristics and demographics, associated mortality can exceed 25 %, with substantial associated increases in health-care costs [ 1 3 ]

Endotracheal reintubation is required in 8–10 % of patients secondary to PRF following major abdominal surgery Although often a necessary supportive inter-vention, endotracheal intubation is an independent predictor of hospital mortality, prolonged intensive care, and hospital stay [ 1 5 ] Noninvasive ventilation (NIV) has been used as both a prophylactic and therapeutic treatment option in patients with PRF after major abdominal surgery and may potentially reduce the signifi cant morbidity and mortality associated with reintubation Early studies examining the use of NIV in this patient group were inconclusive or produced confl icting results [ 6 7 ], but there is now growing evidence and enthusiasm for using NIV postopera-tively to reduce the risk of complications following major surgery This chapter reviews the evidence for the use of NIV in open abdominal visceral surgery, thora-coabdominal surgery, vascular surgery, and transplant surgery

29.2 Etiology of Respiratory Complications

following Abdominal Surgery

Pulmonary function deteriorates in all patients following major abdominal surgery, with a reduction in lung volumes and the development of alveolar collapse and atel-ectasis in 80–90 % of patients Atelectasis leads to hypoxemia via ventilation perfu-sion mismatching Its development signifi cantly increases the risk of PRF and PPCs and may trigger an infl ammatory reaction promoting bacterial growth in the lungs and bacterial translocation into the bloodstream The main disruptions to normal respiratory function are maximal in the fi rst hours following surgery and generally regress after 1–2 weeks

29.3 NIV Following Abdominal Surgery

The use of NIV following major surgery is well established as both a prophylactic and therapeutic treatment modality Although oxygen therapy may be effective in attenuating postoperative hypoxemia, it is only a symptomatic approach that does not reverse the underlying pathophysiological process There is evidence to sug-gest that lung expansion therapy using incentive spirometry and deep-breathing exercises reduces PPCs after abdominal surgery [ 8 ] Compared with standard posi-tive pressure respiratory therapy, the application of continuous NIV is associated with an increase in functional residual capacity and reduced atelectasis and left ventricular afterload, with a subsequent increase in cardiac output and arterial oxygenation

A.J Morgan and A.J Glossop

Studies comparing NIV with standard therapy have generally provided positive results supporting the use of NIV postoperatively, but they are limited by small sample sizes, with a large variation in the modality of NIV, technical implementa-tion, and timing of application seen between studies The small sample sizes in these studies has meant that atelectasis and PaO 2 /FiO 2 (PF) ratio are commonly assessed, which may not translate into clinically relevant end points such as reintu-bation and mortality rates Although reductions in rates of PPCs and reintubation have been demonstrated in the literature, there is currently limited evidence regard-ing the impact of NIV on mortality

A landmark multicenter, prospective, randomized control trial (RCT) of 209 patients published in 2005 by Squadrone et al [ 9 ] demonstrated a signifi cant reduc-tion in reintubation, pneumonia, and sepsis rates following early hood continuous positive airway pressure (CPAP) in hypoxemic patients after elective major abdomi-nal surgery ICU length of stay was lower in the CPAP group, but there was no dif-ference in hospital length of stay or in-hospital mortality between groups In a prospective observational study involving 72 patients with severe PRF after abdom-inal surgery, reintubation was avoided in 67 % of patients treated with NIV [ 10 ]

A large meta-analysis of 654 patients pooled from nine studies of NIV use following abdominal surgery demonstrated that NIV use was associated with a signifi cantly lower rate of PPCs, including atelectasis, when compared with stan-dard medical therapy [ 11 ] The pooled estimate of two studies using intubation as

an endpoint showed a benefi cial effect of CPAP (risk reduction 0.85; 95 % confi dence interval (CI) 0.34–0.97) Two of the studies included in the analysis assessed the effect of postoperative CPAP on mortality following abdominal surgery; how-ever, the number of deaths was too small to allow meaningful analysis The stud-ies included in this meta-analysis displayed marked heterogeneity, differing in both application and duration of CPAP use, and only included preoperatively healthy patients in fi ve studies and may therefore underestimate the benefi cial effects of NIV

CPAP may be of particular benefi t for patients who cannot participate with incentive spirometry or deep-breathing exercises In patients with obstructive air-ways disease, CPAP decreases work of breathing by counterbalancing the inspira-tory threshold load imposed by intrinsic positive-end expiratory pressure (PEEP) Noninvasive positive pressure ventilation (NPPV) may be considered in patients in whom hypercarbia coexists with hypoxemia, when there is a history of chronic obstructive pulmonary disease, or in patients who are experiencing an increased respiratory workload

The optimum amount of PEEP and duration of NIV, particularly as a tic treatment, remains controversial, with a lack of supporting evidence and trials in which a benefi t for NIV has not been evident [ 7 12 ] Some authors have suggested that immediate application of NIV post extubation may be more benefi cial in recruiting alveoli than delayed or intermittent NIV, although current practice varies widely and is often dictated by local preferences and protocols or the need to balance continued alveolar recruitment with patient comfort, nursing availability, and workload

prophylac-29 Noninvasive Ventilation Following Abdominal Surgery

Upper gastrointestinal (GI) surgery in which a surgical anastomosis has been formed has historically been considered a contraindication to NIV because of the theoretical risk of NIV causing increased gastric luminal pressures and subsequent disruption of the surgical anastomosis In a prospective cohort study, 1,067 patients undergoing a gastrojejunostomy as part of a gastric bypass procedure were assessed [ 13 ], and no correlation was found between anastomotic leaks and use of CPAP In

a retrospective review involving 91 patients receiving CPAP after laparoscopic Roux-en-Y gastric bypass surgery, the incidence of anastomotic leakage was zero [ 14] Additionally, transmural gastric pressures have not been demonstrated to increase following the application of CPAP after laparoscopic Roux-en-Y gastric bypass [ 15 ] Despite the lack of RCT data in this area, it would appear that NIV usage is not associated with an increased risk of anastomotic failure and is safe to use following upper GI surgery, although caution should be exercised to avoid high airway pressures (>25 cmH 2 O) It would also seem prudent in NPPV use to limit the maximum Pressure support ventilation (PSV) level to 8 cmH 2 O to prevent genera-tion of excessively high pressures during inspiration

29.4 NIV Following Thoracoabdominal Surgery

Esophageal surgery results in diaphragmatic disruption and a restrictive drome resulting in atelectasis, hypoxemia, and a high incidence of PPCs, and the presence of a transposed gastric conduit may further compromise respiratory function postoperatively Maintenance of adequate postoperative oxygenation is

syn-of importance in preventing impaired oxygen delivery and subsequent ischemia

of the gastric conduit, which are the main risk factors predisposing to motic leakage

Michelet et al [ 16 ] compared the effi cacy of NIV with conventional treatment in

72 patients who developed post-esophagectomy respiratory failure This case- controlled study, in which 36 patients were matched to 36 historical controls, dem-onstrated a reduction in reintubation, frequency of acute respiratory distress syndrome, anastomotic leakage, and intensive care unit (ICU) length of stay in patients treated with NIV compared with controls No reduction in either hospital mortality or length of stay was seen In an RCT including 70 patients undergoing thoracoabdominal gastroesophageal resection, Fagevik Olsén et al [ 4 ] compared standard therapy with prophylactic CPAP in the immediate postoperative period Signifi cantly fewer patients in the CPAP group required reintubation and prolonged

MV Clinical outcomes of ICU and hospital length of stay and 30-day mortality were similar between groups

In this group of patients with a propensity for developing PRF, who are often of

an increased age with multiple comorbidities, NIV support presents an attractive option in the postoperative period to maintain adequate oxygenation and reduce the complications associated with MV The use of NIV does not appear to be associated with anastomotic failure and NIV may be safely used following esophageal surgery

A.J Morgan and A.J Glossop

29.5 NIV Following Vascular Surgery

Repair of a thoracic or abdominal aortic aneurysm is high-risk surgical procedure, with the risk of developing PRF as high as 60 % in some patient groups and MV being required in about 8 % of these patients [ 17 , 18 ] Mortality rates increase four-fold if a patient requires reintubation following the development of PRF Therefore, prevention of respiratory complications in this group of high-risk patients may have

a signifi cant impact on patient morbidity and mortality

Several studies have examined the use of NIV following abdominal surgery and included vascular patients, but only two examined NIV use following vascular sur-gery alone Böhner et al [ 19 ] applied continuous nasal CPAP for at least 12 h in 99 patients post extubation following laparotomy for vascular surgery Supplemental oxygen to maintain arterial oxygen saturations greater than 95 % was used in the control group of 105 patients Severe hypoxemia occurred signifi cantly less fre-

quently in the NIV group (5 % vs 16 %; p = 0.01), and nonstatistically signifi cant

trends toward reductions in the incidence of pneumonia and reintubation were also seen In a prospective randomized trial of 50 patients, Kindgen-Milles et al [ 20 ] compared the application of continuous nasal CPAP at 10 cmH 2 O for a mean of 23 h with standard therapy following thoracoabdominal aortic aneurysm repair Nasal CPAP was associated with signifi cantly fewer pulmonary complications (PF ratio

<100 mmHg, atelectasis, pneumonia, reintubation); a nonsignifi cant reduction in

mean ICU stay and a signifi cant reduction in mean hospital length of stay ( p = 0.048,

8 ± 1 vs 12 ± 2 days) were also seen

The use of NIV prophylactically following major vascular surgery has thus been demonstrated in large RCTs to be benefi cial in terms of preventing complications that result in signifi cant morbidity and burden on health-care resources Although there is no mortality data to support its use in this patient group, NIV use should be strongly considered following major vascular surgery

29.6 NIV Following Solid Organ Transplantation

Postoperative pulmonary complications following solid organ transplantation tribute substantially to morbidity and mortality in this group of patients Approximately 5 % of patients undergoing renal, hepatic, cardiac, or pulmonary transplantation develop postoperative pneumonia The concurrent use of immuno-suppressive therapy to prevent transplant rejection increases the morbidity and mor-tality associated with pulmonary infection In patients with PRF, the need to reintubate is the major factor associated with the development of nosocomial pneumonia

Although the use of NIV to prevent intubation and MV is well established in immunocompromised patients with acute respiratory failure, there is only one ran-domized trial of postoperative NIV use in patients following intra-abdominal organ transplantation Antonelli et al [ 21 ] concluded from an RCT of 40 patients that NIV compared with supplemental oxygen alone signifi cantly improves PF ratios and

29 Noninvasive Ventilation Following Abdominal Surgery

reduces rates of reintubation, fatal complications, and overall ICU mortality in organ transplant recipients (lung, liver, and kidney) with hypoxemic PRF Hospital mortality rate did not differ between the groups A subgroup analysis of the patients undergoing only liver transplantation did not show a signifi cant difference in reintu-bation and mortality rate, a fi nding supported by a subgroup analysis of an observa-tional study by Jaber et al [ 10 ]

29.7 Conclusions and Recommendations

Although few studies have examined different techniques to treat or prevent nary complications and large RCTs in this area are lacking, early NIV is an attrac-tive treatment option following major abdominal surgery because it may provide ongoing respiratory support without the risks of endotracheal intubation and

pulmo-MV When NIV is effective in avoiding reintubation, the morbidity and mortality associated with MV are reduced NIV may also reduce ICU length of stay, which has substantial associated cost benefi ts

There is good evidence to support the early use of NIV (CPAP) in high-risk patients with PRF or PPCs following elective major abdominal surgery, and its use

is recommended in this group to reduce reintubation risk The use of a risk stratifi tion score may assist in identifying the specifi c patient population for whom NIV may be of most benefi t and directing resources toward patients with the most need [ 1 ] When used as prophylaxis, based on limited current evidence, NIV should be applied immediately post extubation and used continuously as tolerated by the patient Future research should focus on determining the optimal NIV regimen in terms of modality, timing, and duration and also address the impact of NIV on mor-tality in high-risk patients

The use of NIV after gastrointestinal surgery involving formation of an mosis is more controversial, although the available literature suggests that NIV is safe to use in patients with respiratory failure following esophageal, gastric, and bariatric surgery as it may reduce reintubation rates without increasing risk of anas-tomotic dehiscence Further work is needed in this area to clarify the mode of deliv-ery, timing, and duration of NIV that is most benefi cial in this patient group The use of NIV as prophylaxis following major vascular surgery has been shown

anasto-to reduce the risks of hypoxia, respiraanasto-tory failure, and need for reintubation, which are all major causes of postoperative morbidity Although evidence of mortality benefi t in this patient group is lacking, the use of NIV to prevent such complications

is recommended There is a paucity of evidence for the use of NIV following plant surgery, although the available evidence suggests that NIV use may be benefi -cial in patients who develop respiratory failure postoperatively to prevent the need for reintubation and the attendant infective risks

Overall, it is evident that the use of NIV in patients following major abdominal surgery is benefi cial, and although there is little data pertaining to mortality benefi t, there is evidence in all patient groups of reductions in major causes of postoperative morbidity and complications, which has important implications for patient safety

A.J Morgan and A.J Glossop

and use of health-care resources Debate continues as to whether NIV is best used

as prophylaxis or treatment in postoperative patients and also whether CPAP or NPPV is the optimal mode of delivery to reduce postoperative complications Future research should focus on mortality as an endpoint, given that the morbidity benefi ts are already well demonstrated, and also debate the optimum mode, timing, and delivery of NIV in high-risk surgical patients

3 Johnson RG, Arozullah AM, Neumayer L, et al Multivariable predictors of postoperative respiratory failure after general and vascular surgery: results from the patient safety in surgery study J Am Coll Surg 2007;204:1188–98

4 Fagevik Olsén M, Wennberg E, Johnsson E, et al Randomized clinical study of the prevention

of pulmonary complications after thoracoabdominal resection by two different breathing niques Br J Surg 2002;89:1228–34

5 Lawrence VA, Hilsenbeck SG, Mulrow CD, et al Incidence and hospital stay for cardiac and pulmonary complications after abdominal surgery J Gen Intern Med 1995;10:671–8

6 Stock M, Downs J, Gauer P, et al Prevention of postoperative pulmonary complications with CPAP, incentive spirometry, and conservative therapy Chest 1985;87:151–7

7 Carlsson C, Sonden B, Thylen U Can postoperative continuous airway pressure (CPAP) vent pulmonary complications after abdominal surgery? Intensive Care Med 1981;7:225–9

8 Lawrence VA, Cornell JE, Smetana GW, et al Strategies to reduce post-operative pulmonary complications after non-cardiothoracic surgery: systematic review for the American College of Physicians Ann Intern Med 2006;144:595–608

9 Squadrone V, Coha M, Cerutti E, et al Continuous positive airway pressure for treatment of post-operative hypoxaemia: a randomized controlled trial JAMA 2005;293:589–95

10 Jaber S, Delay J, Sebbane M, et al Outcomes of patients with acute respiratory failure after nal surgery treated with non-invasive positive-pressure ventilation Chest 2005;128:2688–95

11 Ferrerya GP, Baussano I, Squadrone V, et al Continuous positive airway pressure for treatment

of respiratory complications after abdominal surgery: a systematic review and meta-analysis Ann Surg 2008;247:617–26

12 Denehy L, Carroll S, Ntoumenopoulos G, et al A randomized controlled trial comparing odic mask CPAP with physiotherapy after abdominal surgery Physiother Res Int 2001;6: 236–50

13 Huerta S, DeShields S, Shpiner R, et al Safety and effi cacy of post-operative continuous tive airway pressure to prevent pulmonary complications after Roux-en-Y gastric bypass

posi-J Gastrointest Surg 2002;6:354–8

14 Ramirez A, Labor PF, Szomstein S, et al Continuous positive airway pressure in immediate postoperative period after laparoscopic Roux-en-Y gastric bypass: is it safe? Surg Obes Relat Dis 2009;5:544–6

15 Weingarten TN, Kendrick M, Swain JM, et al Effects of CPAP on gastric pouch pressure after bariatric surgery Obes Surg 2011;21:1900–5

16 Michelet P, D’Journo XB, Seinaye F, et al Non-invasive ventilation for treatment of post- operative respiratory failure after oesophagectomy Br J Surg 2009;96:54–60

17 Money SR, Rice K, Crockett D, et al Risk of respiratory failure after repair of nal aortic aneurysms Am J Surg 1994;168:152–5

thoracoabdomi-29 Noninvasive Ventilation Following Abdominal Surgery

20 Kindgen-Milles D, Muller E, Buhl R, et al Nasal-continuous positive airway pressure reduces pulmonary morbidity and length of hospital stay following thoraco-abdominal surgery Chest 2005;128:821–8

21 Antonelli M, Conti G, Bufi M, et al Noninvasive ventilation for treatment of acute respiratory failure in patients undergoing solid organ transplantation A randomized trial JAMA 2000;283:235–41

A.J Morgan and A.J Glossop

© Springer International Publishing Switzerland 2016

A.M Esquinas (ed.), Noninvasive Mechanical Ventilation and Diffi cult Weaning

in Critical Care: Key Topics and Practical Approaches,

DOI 10.1007/978-3-319-04259-6_30

M Carron , MD ( * ) • A Toniolo , MD

Department of Medicine , Anesthesiology and Intensive Care, University of Padova ,

Via C Battisti, 267 , 35121 Padova , Italy

e-mail: michele.carron@unipd.it ; anna.toniolo84@gmail.com

30

Noninvasive Mechanical Ventilation

in Postoperative Bariatric Surgery

Michele Carron and Anna Toniolo

30.1 Introduction

Obesity has increased worldwide during the past few decades [ 1 , 2 ] Anesthesiologists must provide care for an increasing number of obese patients in their clinical practice Anesthesiologists should consider that the specifi c respiratory problems associated with obesity may increase the risk of postoperative respiratory complications Anesthesia, surgery, and postoperative pain further diminish respiratory function, pre-disposing the obese patient to hypoxemia and acute respiratory failure (ARF) [ 1 , 2 ] Noninvasive ventilation (NIV) may be an important tool for managing obese patients after surgery NIV may reduce the risk of ARF, reintubation, duration of intensive care and hospital stays, morbidity, and mortality in postoperative patients [ 3 ] Major issues surrounding preoperative and postoperative respiratory changes and postoperative application of NIV in obese patient are discussed in this chapter

30.2 Discussion and Analysis

on the mass and height of an individual Obesity is defi ned by a BMI exceeding

30 kg/m 2 [ 1 2 ]

However, BMI is not the ideal measurement of obesity because it fails to convey

an accurate account of the distribution of fat [ 1 ] Fat distribution is very important [ 1 2 ], and can be classifi ed as either android or gynecoid [ 1 ] Although the terms

android and gynecoid refer to the typical male (centripetal) and female (peripheral)

fat distributions, both distributions are observed in both genders [ 1 ] The android type is of greater pathophysiological signifi cance Android fat distribution describes

a physique in which weight is carried on the trunk with a high intraperitoneal fat content By contrast, gynecoid fat describes a physique in which more weight is carried on the arms, legs, and buttocks, and abdominal fat is predominantly extra-peritoneal Compared with the gynecoid fat distribution, the android distribution is more frequently associated with obstructive sleep apnea (OSA) and respiratory changes [ 1 ]

30.2.2 Upper Airway Changes in Obese Patients

Obese patients are predisposed to upper airway obstruction and respiratory failure [ 1 , 2 ] Patency of the upper airway is maintained by the pharyngeal dilator muscles during inspiration, although lung infl ation may also contribute to patency [ 1 , 2 ] Postoperative muscle weakness and upper airway or pharyngeal dysfunction fol-lowing anesthesia may predispose patients to upper airway obstruction, particularly patients with OSA [ 1 3 ] Fat deposition can promote airway collapse and narrow-ing of the upper airway Magnetic resonance imaging studies indicate superfi cial fat deposition at the neck and a greater amount of fat deposition in the lateral pharyn-geal wall, including pharyngeal structures, such as the tongue, uvula, tonsils, tonsil-lar pillars, and aryepiglottic folds [ 1 ] These fi ndings are particularly evident in the android obesity pattern

30.2.3 Changes in Respiratory Function in Obese Patients

Obesity, particularly severe obesity, affects pulmonary function [ 1 5 ] The lation of fat tissue in the chest wall, abdominal cavity, and intrathoracic space decreases compliance and diminishes lung volume Cephalic displacement of the diaphragm increases abdominal content and pulmonary blood volume, further reducing compliance and lung volume [ 1 5 ]

Resting tidal volume normalized to total body weight or lean body weight is reduced by 50 % or 20 %, respectively, in comparison with that of patients with normal weights [ 1 , 2 ] In addition, the respiratory rate may be 40 % higher in obese patients than in nonobese subjects [ 1 2 ] Forced vital capacity (FVC), forced expi-ratory volume in 1 s (FEV 1 ), functional residual capacity (FRC), expiratory reserve volume (ERV), total lung capacity (TLC), and maximal voluntary ventilation are reduced, particularly among morbidly obese patients [ 2 ] Because both FEV 1 and

M Carron and A Toniolo

Mechanical pulmonary function is further altered by physiological changes that are present in the obese state [ 1 , 2 ] Increased lean body weight and fat tissue increases oxygen consumption and carbon dioxide production to satisfy metabolic requirements These changes increase minute ventilation [ 1 2 ] Oxygen consump-tion is increased at rest by approximately 25 % in obese subjects [ 1 , 2 ] Despite increased production of carbon dioxide, normocapnia is usually maintained by the increased minute ventilation [ 1 , 2 ] Patients with chronic obstructive pulmonary disease (COPD) or obesity hypoventilation syndrome are generally hypercapnic [ 1 ,

2] Increased upper airway resistance, restrictive pulmonary pathophysiology, increased minute ventilation, oxygen consumption, carbon dioxide production, and respiratory muscle dysfunction due to increased cytokine levels and fatty infi ltration signifi cantly increase the effort required to breathe [ 1 2 ] Normocapnic, morbidly obese subjects exhibit increased breathing effort at rest by about 30–70 % In severe obesity, effort required may increase up to 280 % of normal, leading to a 10-fold increase in the energy cost of breathing [ 1 2 ]

Altered pulmonary function in obese patients affects pulmonary gas exchange, especially among those with BMIs that exceed 40 kg/m 2 [ 1 , 2 ] Morbidly obese patients may have reduced partial arterial oxygen concentrations (PaO 2 ), increased partial arterial carbon dioxide concentrations (PaCO 2 ), and increased alveolar-to- arterial oxygen partial pressure differences The increased shunt fraction and the ventilation-perfusion mismatch result in hypoxemia [ 1 2 ]

30.2.4 Postoperative Changes in Respiratory Function

and Impact on Postoperative Outcome

Anesthesia, surgery, and postoperative pain further reduce respiratory function [ 1 2 ] Airway resistance and respiratory system elastance increase up to 60 % and

50 %, respectively, whereas the FRC decreases by about 60 % [ 4 , 5 ] Reduced lung volume, modifi ed breathing patterns, diaphragm dysfunction, and postoperative pain favor low tidal volume ventilation These changes collectively promote alveo-lar hypoventilation, hypoxemia, hypercapnia, and increased atelectasis, which pre-dispose the patient to pneumonia [ 1 3 6 ]

The Nationwide Inpatient Sample database documents 304,515 patients as receiving bariatric surgery between 2006 and 2008, with an overall ARF rate of 1.35 % The greatest rate of ARF (4.10 %) was observed after open gastric bypass surgery The ARF rate was lower after laparoscopic surgery compared with that

after open surgery (0.94 % vs 3.87 %, p < 0.01) or after nongastric bypass versus gastric bypass (0.82 % vs 1.54 %, p < 0.01) [ 7 ] Age, BMI, ASA =American Society

of Anesthesiologists physical status, metabolic syndrome, and additional

30 Noninvasive Mechanical Ventilation in Postoperative Bariatric Surgery

comorbidities are associated with an increased risk of postoperative respiratory complications (i.e., pneumonia, atelectasis, respiratory failure, adult respiratory dis-tress syndrome) [ 1 3 ] Despite a relatively low incidence, postoperative ARF may represent a life-threatening event A retrospective analysis of a large prospective database from 1996 to 2006, including 13,871 bariatric surgical procedures, showed that ARF was the fourth cause of mortality (11.8 %) [ 8 ]

30.2.5 Noninvasive Ventilation Techniques and Device

Continuous positive airway pressure (CPAP) and non-invasive positive pressure ventilation (NPPV) have been proposed for use during the postoperative period in obese patients [ 2 3 ]

CPAP is a method that delivers constant positive airway pressure noninvasively during both inspiration and expiration [ 3 ] When CPAP is applied with positive inspiratory ventilatory support (PSV), it is referred to as positive end-expiratory pressure (PEEP) [ 3 ] CPAP decreases upper airway obstruction and prevents airway and alveolar collapse This action reduces atelectasis and increases FRC by recruit-ing and stabilizing previously collapsed lung tissue, reducing ventilation/perfusion mismatch and shunt fraction with improved gas exchange [ 2 3 ] CPAP counteracts the effect of increased abdominal pressure on the diaphragm and decreases the work

of breathing, counterbalancing the inspiratory threshold load imposed by intrinsic PEEP in some patients (i.e., COPD patients) [ 2 , 3 ] Furthermore, CPAP reduces left ventricular afterload and increases cardiac output [ 2 3 ]

NPPV refers to PSV with or without PEEP and BiPAP (bi-level positive airway pressure) [ 3 ] BiPAP is a technique that delivers two positive airway pressures [ 3 ]

In fact, BiPAP includes PSV plus PEEP and CPAP, in which the later delivers only one positive airway pressure In comparison to that achieved with CPAP, PSV above PEEP achieves improved muscle unloading and relief from dyspnea during NIV [ 3 ] PSV plus PEEP increases the alveolar ventilation obtained with CPAP alone [ 2 3 ]

It is diffi cult to establish a standard recommendation for all obese patients An individual titration should be performed to fi nd the best NIV setting to reduce dys-pnea, unload respiratory muscles, increase oxygenation, and counteract the effect of increased abdominal pressure on the diaphragm in obese patients after surgery [ 2 , 3 ] Patient selection and monitoring are crucial for reducing NIV failure [ 6 ] NIV should never be initiated in uncooperative and/or hemodynamically unstable patients [ 6 ] Such patients need prompt tracheal intubation to allow conventional ventilation; delayed ventilation is associated with increased morbidity and mortality [ 6 ]

During NIV, gas is delivered to the airway via an interface (nasal or facial mask or helmet) [ 2 6 ] The appropriate selection and adequate management of a device are crucial for minimizing the risk of complications and failure during NIV [ 2 6 ] It is important to choose an interface that fi ts properly and minimizes air leaks and to allow the patient to become familiar with the equipment in the fi rst few minutes of NIV [ 2 ,

6 ] In patients who feel claustrophobic, the use of different sizes or types of masks or helmets may enhance patient comfort [ 2 6 ] To date, there is no evidence supporting

M Carron and A Toniolo

the use of a specifi c patient interface device in obese patients [ 2 , 6 ] However, the use

of a helmet may improve patient comfort and compliance Helmets are better tolerated than masks, resulting in longer use and lower NIV failure rates [ 6 ]

Prevention and management of gastric insuffl ation may be achieved by placing a nasogastric tube for intermittent air and fl uid aspiration prior to NIV [ 2 , 6 ] Antacid prophylaxis should be considered for reducing gastric content and vomiting after gastric insuffl ation to avoid serious complications (i.e., pulmonary aspiration, pneu-monia, and possibly death) [ 2 6 ]

30.2.6 Rationale for Postoperative NIV in Obese Patients

Postoperative NIV can be used in a prophylactic or curative manner during bariatric surgery Prophylactic use involves treating postoperative changes in respiratory function to prevent postoperative ARF Curative use occurs after ARF develops and

is aimed toward alleviating respiratory failure and avoiding tracheal intubation, which is associated with increased morbidity and mortality [ 3 ]

30.2.6.1 Postoperative Prophylactic Use of NIV in Obese Patients

Gaszynski et al [ 9 ] compared postoperative Boussignac CPAP delivered through a facial mask with traditional oxygen delivery via nasal catheter in 19 morbidly obese patients after open Roux-en-Y gastric bypass [ 9 ] CPAP improved blood oxygen-ation compared with that achieved with standard treatment (PaO 2 81.0 ± 16.0 vs

65.9 ± 4.9 mmHg, p < 0.05) without infl uencing carbon dioxide clearance [ 9 ] Neligan et al [ 10 ] compared the effect of Boussignac CPAP (CPAP System; Vitaid; Toronto, CA) on lung function to that of supplemental oxygen alone after extubation of 40 morbidly obese patients with known OSA who received laparo-scopic bariatric surgery [ 10 ] FEV 1 , FVC, and peak expiratory fl ow were increased

by 35 % after administering CPAP immediately after extubation for the duration of stay in the PACU (post-anesthesia care unit) and by 22 % after CPAP was applied for at least 8 h overnight [ 10 ]

El-Solh et al [ 11 ] evaluated NIV immediately after extubation of 62 consecutive severely obese patients NIV was delivered by the BiPAP mode (BiPAP S/T-D Ventilatory Support System; Respironics Inc.; Murrysville, PA, USA) through a nasal mask [ 11 ] Compared with conventional therapy, BiPAP resulted in a 16 % absolute risk reduction in the rate of respiratory failure [ 11 ] There were signifi cant differences

in the lengths of intensive care unit (ICU) and hospital stays between the two groups [ 11 ] Subgroup analysis of hypercapnic patients showed a reduced number of hospital mortalities in the NIV group compared with that of the control group [ 11 ]

Joris et al [ 12 ] investigated the effect of BiPAP (BiPAP System; Respironics Inc.; Murrysville, PA, USA) delivered through a nasal mask on postoperative pulmonary function in 33 morbidly obese patients after gastroplasty Patients were assigned to one of three types of ventilatory support during the fi rst 24 h postoperatively: oxygen via face mask, BiPAP 8/4, or BiPAP 12/4 [ 12 ] Patients in the two BiPAP groups used the mask at least 2 h out of every 3 h during the fi rst 24 h postoperatively [ 12 ] The

30 Noninvasive Mechanical Ventilation in Postoperative Bariatric Surgery

use of BiPAP 12/4, but not 8/4, allowed signifi cant reduction in the magnitude of pulmonary dysfunction after gastroplasty [ 12 ] FVC and FEV 1 were more than 50 % greater in the BiPAP 12/4 group compared with those in the control group during 3 days of follow-up observation [ 12 ] The peak expiratory fl ow rate was also increased

in the BiPAP 12/4 group ( p = 0.10) [ 12 ] Improved pulmonary function was ated with a signifi cant increase in oxygenation in both BiPAP groups [ 12 ]

Zoremba et al [ 13 ] prospectively studied 60 obese patients undergoing minor peripheral surgery Half were randomly assigned to receive short-term NPPV (PSV + PEEP; Dräger AG; Lübeck, Germany) through full face masks during their PACU stays; the others received supplemental oxygen via Venturi masks [ 13 ] Pulmonary function in the NPPV group was signifi cantly better than that in the

control group ( p < 0.0001) [ 13 ] Blood gas levels and the alveolar to arterial oxygen

partial pressure difference were also improved ( p < 0.03) [ 13 ] These effects

per-sisted for at least 24 h after surgery ( p < 0.05) [ 13 ] (Fig 30.1 )

30.2.6.2 Postoperative Curative Use of NIV in Obese Patients

No data are available in the literature regarding the role of NIV for postoperative treatment of ARF in obese patients

In a study of 72 nonobese patients with ARF after abdominal surgery who were treated with NPPV (PSV + PEEP; Servo-Ventilator 300; Siemens; Elema, Sweden; or Evita 4; Dräger Medical; Lübeck, Germany) via face mask, Jaber

et al [ 14 ] found that 67 % of patients avoided intubation [ 14 ] Within the fi rst NPPV observation period, a signifi cant benefi t was observed only in the NPPV group, with increased PaO 2 /FiO 2 (+36 ± 29), decreased respiratory rate (from 28.2 ± 3.4 to 23.1 ± 3.8 breaths/min), reduced length of ICU stay, and reduced mortality rate [ 14 ]

Fig 30.1 Postoperative use of NIV in obese patients ( a ) Prophylactic use of CPAP in an obese

patient after laparoscopic sleeve gastrectomy through a CPAP mask with integral Venturi fl ow

driver and adjustable PEEP valve (Ventumask; StarMed; Mirandola, Italy) ( b ) Therapeutic use of

NPPV (PSV + PEEP) in an obese patient with respiratory failure after gastric bypass surgery ered by a helmet for NIV (CaStar R; StarMed; Mirandola, Italy) Written informed consent was obtained from patients

deliv-M Carron and A Toniolo

One meta-analysis showed that NIV reduced reintubation rates (odds ratio (OR) 0.24), incidence of pneumonia (OR 0.27), and ICU length of stay (0.44 days) when applied after major surgery [ 15 ] There was insuffi cient evidence to suggest that NIV improves ICU survival, but an increased hospital survival was observed when NIV was used after surgery (OR 4.54) [ 15 ]

Conclusion

Obese patients present preoperative changes in respiratory function Anesthesia and surgery can profoundly impair respiratory function, increasing the risk of postoperative respiratory complications and ARF Evidence supports early administration of NIV as a prophylactic and as a therapeutic tool after surgery in obese patients for improving respiratory function and gas exchange Selection of the correct interface (face or nasal mask vs helmet) and the type of NIV (CPAP

vs NPPV) together with proper monitoring of the patient during NIV is mental for increasing the likelihood of success of NIV

Confl ict of Interest Disclosure The authors have no interests to disclose

Key Major Recommendations

• Obese patients have a restrictive pattern, which includes reduced lung ume and compromised respiratory system compliance Obese patients may

vol-be hypoxemic with increased at-rest consumption of oxygen Carbon ide is usually close to normal

diox-• Anesthesia, surgery, and postoperative pain further reduce lung volumes, altering respiratory mechanics and gas exchange

• Early administration of NIV should be considered as a prophylactic and therapeutic tool in obese patients after surgery to improve respiratory func-tion and gas exchange and to avoid respiratory failure

• CPAP essentially decreases upper airway obstruction and increases genation by recruiting and stabilizing previously collapsed lung tissue, increasing lung volumes NPPV unloads respiratory muscles, relieves dys-pnea, and reduces the work required for breathing

oxy-30 Noninvasive Mechanical Ventilation in Postoperative Bariatric Surgery

4 Pelosi P, Croci M, Ravagnan I, et al Total respiratory system, lung, and chest wall mechanics

in sedated-paralyzed postoperative morbidly obese patients Chest 1996;109:144–51

5 Pelosi P, Croci M, Ravagnan I, et al Respiratory system mechanics in sedated, paralyzed, morbidly obese patients J Appl Physiol 1997;82:811–8

6 Carron M, Freo U, BaHammam AS, et al Complications of non-invasive ventilation techniques:

a comprehensive qualitative review of randomized trials Br J Anaesth 2013;110:896–914

7 Masoomi H, Reavis KM, Smith BR, et al Risk factors for acute respiratory failure in bariatric surgery: data from the Nationwide Inpatient Sample, 2006–2008 Surg Obes Relat Dis 2013;9:277–81

8 Morino M, Toppino M, Forestieri P, et al Mortality after bariatric surgery: analysis of 13,871 morbidly obese patients from a national registry Ann Surg 2007;246:1002–7

9 Gaszynski T, Tokarz A, Piotrowski D, et al Boussignac CPAP in the postoperative period in morbidly obese patients Obes Surg 2007;17:452–6

10 Neligan PJ, Malhotra G, Fraser M, et al Continuous positive airway pressure via the Boussignac system immediately after extubation improves lung function in morbidly obese patients with obstructive sleep apnea undergoing laparoscopic bariatric surgery Anesthesiology 2009;110:878–84

11 El-Solh AA, Aquilina A, Pineda L, et al Noninvasive ventilation for prevention of post- extubation respiratory failure in obese patients Eur Respir J 2006;28:588–95

12 Joris JL, Sottiaux TM, Chiche JD, et al Effect of bi-level positive airway pressure (BiPAP) nasal ventilation on the postoperative pulmonary restrictive syndrome in obese patients under- going gastroplasty Chest 1997;111:665–70

13 Zoremba M, Kalmus G, Begemann D, et al Short term non-invasive ventilation post-surgery improves arterial blood-gases in obese subjects compared to supplemental oxygen delivery – a randomized controlled trial BMC Anesthesiol 2011;11:10

14 Jaber S, Delay JM, Chanques G, et al Outcomes of patients with acute respiratory failure after abdominal surgery treated with noninvasive positive pressure ventilation Chest 2005;128:2688–95

15 Glossop AJ, Shephard N, Bryden DC, et al Non-invasive ventilation for weaning, avoiding reintubation after extubation and in the postoperative period: a meta-analysis Br J Anaesth 2012;109:305–14

M Carron and A Toniolo

© Springer International Publishing Switzerland 2016

A.M Esquinas (ed.), Noninvasive Mechanical Ventilation and Diffi cult Weaning

in Critical Care: Key Topics and Practical Approaches,

DOI 10.1007/978-3-319-04259-6_31

E Calvo-Ayala , MD • P E Marik , MD, FCCM, FCCP ( * )

Division of Pulmonary and Critical Care Medicine, Department of Medicine, EVMS ,

Eastern Virginia Medical School , 825 Fairfax Ave, Suite 410 , Norfolk , VA 23507 , USA

e-mail: marikpe@evms.edu

31

Noninvasive Ventilation After

Extubation in Obese Critically Ill

31.2 Effects of Obesity in the Respiratory System

and Physiologic Usefulness of Noninvasive Ventilation

Obese subjects have an increased oxygen demand as a consequence of the increased body mass from excess adipose tissue [ 7 ] Meeting this high oxygen demand is challenging because obesity affects the respiratory system at different levels (lung

mechanics, lung ventilation/perfusion, respiratory muscles, and upper airways obstruction) [ 8 9 ] Lung mechanics and lung volumes are signifi cantly affected by obesity There is consensus that lung volumes are signifi cantly reduced in obese individuals, particularly functional residual capacity and expiratory reserve volume, leading to a restrictive ventilatory defect [ 10 – 12 ] This restrictive defect is wors-ened by a generalized stiffness and low compliance of the respiratory system, which has been attributed to increased blood volume within the lungs (caused by the aug-mented cardiac output from increased oxygen demand from excess adiposity), low lung volumes, and an overall low chest wall compliance [ 8 ] These changes are exacerbated by a high airway resistance caused by parapharyngeal fat deposition in the upper airway and low forced expiratory volume in 1 sec (FEV1) in these sub-jects, suggesting small airway remodeling

Obese subjects also have a ventilation/perfusion mismatch Although, in obesity, the lower lung zones are well perfused, because of the aforementioned reasons, there is closure of small airways in this region, making the lower zones relatively hypoventilated This closure of the small airways in the bases causes the ventilation

to be redistributed to the upper lobes, which are usually hypoperfused, resulting in

a ventilation-perfusion mismatch with subsequent hypoxemia Lastly, obese jects have respiratory muscle insuffi ciency from lack of endurance and fatigue from increased work of breathing and relatively high oxygen consumption These factors all lead to increased risk of respiratory failure resulting from low respiratory reserve Noninvasive ventilation (NIV) helps overcome some of the aforementioned effects of obesity by (a) “stenting” the upper airway; (b) unloading the respiratory muscles, reducing the work of breathing; and (c) increasing the lung volume, aug-menting alveolar ventilation and reversing atelectasis [ 13 ]

sub-31.3 Weaning Mechanical Ventilation in the Obese Patient:

The Role of NIV

International guidelines and consensus statements recommend liberating patients from mechanical ventilation as soon as possible while making every effort to decrease the chances for reintubation [ 14 , 15 ] The steps required to achieve these goals include assessment of readiness for extubation, performance of a spontaneous breathing trial, and consideration of NIV after extubation These basic principles should be applied to obese critically ill subjects with some modifi cations

Once the underlying triggering factor for respiratory failure has been identifi ed and adequately treated, clinical assessments are needed to determine the patient’s readiness for discontinuation of ventilator support and extubation Although there is

no consensus about the parameters that need to be met to deem a patient “ready” for extubation, in general, there should be adequate oxygenation (SpO 2 > 90 % or PaO 2 > 60 mmHg), adequate acid base status (pH of 7.40 ± 0.05), hemodynamic sta-bility, and adequate mental status The fi rst (and probably most important) consid-eration in obese subjects is that, because of their relatively high intrapleural pressure, the level of positive end-expiratory pressure (PEEP) that is needed to keep the

E Calvo-Ayala and P.E Marik

alveoli recruited may be higher than the level recommended by the guidelines to deem the patient ready (usually the guidelines recommend a PEEP between 5 and

8 cmH 2 O) [ 14 ] In general, because of the altered lung mechanics in obese subjects,

we advocate the measurement of esophageal pressures as a surrogate for the pleural pressure, with titration of PEEP to maintain the transpulmonary pressure gradient (pressure in the airway – pleural pressure) between 0 and 5 cm H 2 O [ 16 ] In our experience, the mean end-expiratory esophageal pressure of severely morbidly obese subjects is approximately 17 cmH 2 O [ 17 ], which means that these patients should be kept on a relatively high PEEP even when considering extubation This requirement is one of the justifi cations to extubate these patients to NIV If the esophageal manometry is not available, it is reasonable to keep the PEEP between

10 and 15 cmH 2 O based on previously published observational studies [ 8 ] These data suggest that obese subjects can be deemed ready for extubation if they meet the aforementioned criteria, even if the PEEP is relatively high

Once the subject is ready for extubation, then the next step is to proceed with a spontaneous breathing trial (SBT) Although the literature recommends the use of either a T-piece trial or a trial under PEEP and some pressure support ventilation, based on the lung mechanics of the obese subjects it is recommended that they undergo a SBT maintaining the same level of PEEP used during the acute phase with some pressure support The criterion for failure of SBT in obese subjects does not differ from the general population and includes tachypnea, hypoxemia, tachy-cardia, hemodynamic instability, or signs of respiratory distress (thoracoabdominal paradox, use of accessory muscles for respiration) If none of the criteria for failure are present during the SBT, then extubation should follow If a high level of PEEP has been maintained during the weaning process, it is reasonable to extubate to NIV Even if the PEEP is at a low level (<8 cmH 2 O), NIV should still be considered

in obese subjects being liberated from invasive mechanical ventilation

31.4 Preparing for NIV After Extubation

As reviewed above, NIV overcomes many of the obesity-related physiologic malities that affect the respiratory system There are, however, no randomized con-trolled trials that have investigated the effects of NIV when used after extubation in critically ill obese subjects A single before-after study has shown a positive out-come (decreased length of ICU and hospital stays) with NIV in obese patients [ 18 ] Studies performed in the postoperative period have shown benefi cial outcomes when NIV is used routinely after extubation [ 19 , 20 ] Because of the anticipated need for high pressure, a facial mask is preferred in these cases Adequate fi tting of the face mask is essential for optimal use of NIV Face masks have the advantage of achieving a better seal with less air leak and better minute ventilation [ 21 ] Based on previously published data and our experience, we recommend extubating obese patients directly to bi-level positive airway pressure ventilation The inspiratory positive airway pressure (iPAP) should be titrated to optimize minute ventilation There is no consensus on the amount of iPAP that needs to be provided in this

abnor-31 Noninvasive Ventilation After Extubation in Obese Critically Ill Subjects

particular setting, however, it is acceptable to start with a pressure difference between iPAP and expiratory positive airway pressure (ePAP) of at least 6–7 cmH 2 O, but higher pressures may be required to achieve the desired ventilation With the same rationale, ePAP should be high enough to overcome the high intrapleural pres-sure of these subjects and should be kept around the same level as the PEEP prior to extubation

There is no standard approach to weaning patients from NIV In general, NIV is discontinued for short periods of time to allow for facial hygiene, oral medications, and small sips of fl uid and enteral nutrition supplements If there is immediate dete-rioration, then NIV is resumed, however, the goal should be to progressively increase the periods of time where the patient is off NIV We usually attempt to continue intermittent NIV support indefi nitely At this point, we initiate a diagnostic workup

to document the presence of obesity hypoventilation syndrome (OHS), sleep apnea,

or both so that patients can be discharged with positive airway pressure therapy that they can use at home

Confl ict of Interest None

• NIV is an option when considering extubation of obese subjects

• High PEEP and ePAP is recommended when using mechanical ventilation

in obese individuals We strongly recommend the use of esophageal manometry to guide this decision

• Because of the advantages of tidal volume delivery and less leakage, we recommend the use of a full face mask when using NIV in obese subjects

• There is no consensus on how to wean patients from NIV We recommend the use of intermittent NIV (with naps and during sleep) for an indefi nite period of time in patients who meet criteria for OHS or sleep apnea

E Calvo-Ayala and P.E Marik

Respiratory failure Am J Respir Crit Care Med 2001;163(1):283–91

14 MacIntyre NR, Cook DJ, Ely Jr EW, et al Evidence-based guidelines for weaning and tinuing ventilatory support: a collective task force facilitated by the American College of Chest Physicians; the American Association for Respiratory Care; and the American College of Critical Care Medicine Chest 2001;120(6 Suppl):375S–95

15 Boles JM, Bion J, Connors A, et al Weaning from mechanical ventilation Eur Respir J 2007; 29(5):1033–56

16 Akoumianaki E, Maggiore SM, Valenza F, et al The application of esophageal pressure surement in patients with respiratory failure Am J Respir Crit Care Med 2014;189(5): 520–31

17 Marik PE, Desai H Characteristics of patients with the “malignant obesity hypoventilation syndrome” admitted to an ICU J Intensive Care Med 2013;28(2):124–30

18 El-Solh AA, Aquilina A, Pineda L, Dhanvantri V, Grant B, Bouquin P Noninvasive ventilation for prevention of post-extubation respiratory failure in obese patients Eur Respir J 2006; 28(3):588–95

19 Pankow W, Hijjeh N, Schuttler F, et al Infl uence of noninvasive positive pressure ventilation

on inspiratory muscle activity in obese subjects Eur Respir J 1997;10(12):2847–52

20 Huerta S, DeShields S, Shpiner R, et al Safety and effi cacy of postoperative continuous tive airway pressure to prevent pulmonary complications after Roux-en-Y gastric bypass

posi-J Gastrointest Surg 2002;6(3):354–8

21 Navalesi P, Fanfulla F, Frigerio P, Gregoretti C, Nava S Physiologic evaluation of noninvasive mechanical ventilation delivered with three types of masks in patients with chronic hypercap- nic respiratory failure Crit Care Med 2000;28(6):1785–90

31 Noninvasive Ventilation After Extubation in Obese Critically Ill Subjects

© Springer International Publishing Switzerland 2016

A.M Esquinas (ed.), Noninvasive Mechanical Ventilation and Diffi cult Weaning

in Critical Care: Key Topics and Practical Approaches,

DOI 10.1007/978-3-319-04259-6_32

F Racca , MD ( * )

Anesthesiology and Intensive Care Unit , SS Antonio Biagio e Cesare Arrigo Hospital ,

Alessandria , Italy

S.C Anestesia e Rianimazione Pediatrica Azienda Ospedaliera SS Antonio Biagio e Cesare

Arrigo , Via Venezia 16 , 15100 Alessandria , Italy

Noninvasive Mechanical Ventilation

in Patients with Neuromuscular Disease

Fabrizio Racca , Chiara Robba , and Maria Pia Dusio

32.1 Introduction

Respiratory failure is the most common cause of morbidity and mortality in patients with progressive neuromuscular diseases (NMDs) [ 1 4 ] The wide variety of NMDs that can affect respiratory function are listed in Table 32.1 NMDs are often compli-cated by progressive involvement of the respiratory muscles and can lead to both chronic and acute respiratory failure (ARF) Reduced inspiratory muscle strength can result in ineffective alveolar ventilation, and weakness of expiratory muscles can lead to inadequate clearance of airway secretions Thus, these conditions can cause chronic respiratory failure as well as potentially life-threatening problems [ 5 – 10 ]

Once patients with NMDs develop respiratory failure, noninvasive mechanical ventilation (NIV) combined with techniques of manually or mechanically assisted coughing are the main therapeutic interventions to support their respiratory function [ 5 – 10 ] This chapter reviews the pathophysiological mechanisms responsible for respiratory failure in patients with slowly progressive NMDs (e.g., amyotrophic lateral sclerosis (ALS), spinal muscular atrophy (SMA), Duchenne muscular dys-trophy (DMD)) and the issues concerning their respiratory care during ARF We do

evolu-32.2 Mechanisms Underlying Respiratory Failure in NMDs

Patients with NMDs can develop respiratory failure because of an imbalance between respiratory load and muscle strength, resulting in ineffective alveolar ven-tilation and hypercapnia The main determinant of this process is the respiratory muscles’ weakness [ 3 ] In addition, patients with slowly progressive NMD have a chronically elevated respiratory load, which leads to increased work of breathing [ 11 – 13 ] The main contributions to the increased mechanical load are as follows:

1 Inability to achieve an effective lung expansion, resulting in progressive

occur-rence of microatelectasis [ 12 , 13 ]

2 Stiffening of the chest wall, caused by muscle atrophy, osteoporosis, and in some

cases extra-articular contractures and intra-articular adhesions, progressing to the irreversible degeneration of the joint cartilage of the rib cage [ 14 ]

3 Spinal deformities (e.g., thoracic scoliosis), contributing to increased work of

breathing [ 11 ] and leading to mechanical embarrassment of the respiratory cles, impairing their contractile function [ 12 ]

As the NMD progresses, nocturnal respiratory dysfunction becomes evident and can result in hypercapnia that is initially limited to sleep With the progression of the NMD, hypoventilation becomes chronic, resulting in daytime hypercapnia Additionally, weakness of expiratory muscle leads to inadequate clearance of air-way secretions

Table 32.1 Neuromuscular diseases affecting respiratory function in children

1 Motor neuron diseases: Spinal muscular atrophy (SMA), amyotrophic lateral sclerosis

(ALS)

2 Peripheral neuropathies: Guillain–Barré syndrome (GBS), chronic infl ammatory

demyelinating polyneuropathy (CIDP), critical illness polyneuropathy

3 Disorders of neuromuscular junction: Myasthenia gravis (MG)

4 Myopathies

4.1 Progressive muscular dystrophies: Duchenne muscular dystrophy (DMD),

facioscapulohumeral muscular dystrophy (FSHD), limb-girdle muscular dystrophies (LGMD), myotonic dystrophies

4.2 Congenital myopathies (e.g., central core diseases, myotubular myopathy, nemaline

myopathy, myofi brillar myopathies)

4.3 Congenital muscular dystrophies (e.g., merosin-defi cient CMD)

4.4 Metabolic myopathies (Mitochondrial myopathies, glycogen storage diseases)

F Racca et al.

as pneumonia, aspiration, atelectasis, and pneumothorax [ 18 , 19 ] During these events, the inspiratory muscles’ strength cannot compensate for the increased respi-ratory load, resulting in impaired alveolar ventilation Moreover, weakness of expi-ratory and bulbar muscle causes ineffective coughing and airway mucus accumulation that further increases the work of breathing, leading to respiratory distress [ 15 – 17 , 20 ].

Patients with NMD usually experience mild to moderate bulbar dysfunction, with the exception of patients diagnosed with type 1 SMA and ALS, who may develop a severe glottis functional impairment Bulbar muscle weakness (facial, oropharyngeal, and laryngeal muscles) can affect the ability to swallow, leading to

a risk of aspiration

Additionally, several myopathies (DMD, limb-girdle muscular dystrophies, myotonic dystrophies, myofi brillar myopathies, mitochondrial myopathies, and glycogen storage diseases) are associated with cardiac dysfunctions (dilated cardio-myopathy and/or abnormalities of the conduction system) [ 21 , 22 ], which may also contribute to the development of ARF [ 23 ]

In NMD patients with compromised respiratory function, anesthetic agents may further decrease respiratory muscles strength and can exacerbate hypoventi-lation, airway secretions retention, aspiration, and obstructive and central apneas [ 5 , 7 , 24 ] These conditions may lead to nosocomial infections, prolonged intuba-tion, tracheotomy, and eventually death Therefore, in all patients with NMDs, preoperative pulmonary evaluation is strongly recommended to assess the risk of respiratory complications and when respiratory function measurements and/or sleep studies are abnormal, NIV and assisted cough techniques may be indicated [ 5 7 24 ]

Table 32.2 Causes of acute exacerbations of chronic respiratory failure in children with NMD

Upper respiratory tracts infections

Tracheal hemorrhage (patients with tracheostomy)

Acute gastric distension (patients under mechanical ventilation)

Abuse of sedative drugs

Postoperative respiratory failure

Pulmonary embolism

32 Noninvasive Mechanical Ventilation in Patients with Neuromuscular Disease

32.3 Diagnostic Process

The early identifi cation of precipitants to intensive care admission (Table 32.2 ) is essential because they are more amenable to therapy than the NMD itself [ 10 , 18 ,

25 – 28 ] The overall diagnostic process is summarized below [ 10 ]

• History: rule out abuse of sedative drugs, aspiration, and anticipatory care plan

(i.e., a do not intubate order)

• Physical examination: rule out signs and symptoms of:

– Heart failure (pulmonary crackles, peripheral edema, elevated jugular venous pressure, pleural effusion, hepatic congestion)

– Clinical signs of pneumonia, aspiration, or atelectasis

– Electrocardiogram to rule out arrhythmias and conduction defects

– Chest X-ray to rule out cardiomegaly, pulmonary congestion, new pulmonary infi ltrate, and pneumothorax (mandatory computed tomography (CT) scan in case of suspected pneumothorax and non-conclusive chest X-ray)

– Echocardiogram to evaluate ventricular function if heart failure is suspected

It is important to note that pneumothorax is a rare but serious and life-threatening complication in NMD patients Conventional chest X-ray has poor sensitivity for the detection of pneumothoraces and thoracic CT may be required [ 18 ]

tech-F Racca et al.

Invasive ventilation should be considered if, despite 6–12 h of NIV with optimal ventilator settings, it proves impossible to reduce dyspnea or lethargy, to decrease the respiratory rate, or to improve blood gas exchange (i.e., refractory arterial pH below 7.30 or below the value on admission or failure to maintain a PaO 2 > 65 mmHg with a FIO 2 ≥ 0.6) [ 27 , 36 ]

Hospital admission can be disruptive for these patients [ 38 ], who can often be cessfully managed at home by experienced and well-trained family members [ 30 ] Bach and colleagues [ 16 , 17 , 29 , 39 ] described a regimen for managing acute on chronic neuromuscular respiratory failure at home The patients received a 24-h NIV during the exacerbation periods Oxygen saturation of room air was monitored con-tinuously and when it fell below 95 %, secretions were aggressively removed using MI-E (mechanical insuffl ation-exsuffl ation) until oxygen saturation returned to the

suc-95 % range Although controlled studies establishing the effi cacy of this approach are lacking, the authors reported a dramatic reduction in the need for hospitalization and

a prolongation of life expectancy Vianello et al [ 40 ] showed that “hospital at home” for NMD patients with respiratory tract infection for whom hospital admission had been recommended after medical assessment is an effective alternative to hospital admission They treated these patients according to the following treatment protocol:

• District nurses visited the subjects mornings and afternoons until recovery from exacerbation The nurse assessed the subject’s adherence and response to treat-ment and could request a pulmonology visit if clinical progress was unsatisfactory

• A pulmonologist visited the subjects each morning for the fi rst 3 days, and after at the discretion of the district nurses or subject’s general practitioner, to assess the response to therapy and eventually introduce changes

there-• Subject telephone access to the pulmonologists was ensured

• The subjects’ general practitioners were informed of the subjects being ized to the hospital-at-home program

random-• Standard antibiotic therapy was used, following guidelines for the management

of acute bronchitis or community-acquired pneumonia

• The ventilator was readjusted to obtain a tidal volume of 10–12 ml/kg and a breathing frequency of <25 breaths/min and to maintain SpO 2 ≥ 95 % NIV was initially delivered continuously, except for 30–60 min periods of “rest” to allow the subject to receive liquid dietary supplements, drink water, and speak After the fi rst 24–48 h, if clinical conditions and blood gas exchange were satisfactory, the application of NIV was interrupted by progressively longer intervals of spontaneous breathing In all cases, nocturnal ventilation via nasal mask was continued until the end of the follow-up period

32 Noninvasive Mechanical Ventilation in Patients with Neuromuscular Disease

treat-of the device Subsequently, assisted cough was independently administered by home caregivers

• Hospital-at-home subjects received pulse oximeter monitoring, and their givers were instructed to perform assisted coughing, NIV, or both as needed to return SpO 2 ≥ 95 %

If home management fails, patients must be hospitalized and they should be managed in an ICU, where a cough machine and NIV should be applied aggres-sively NIV and assisted coughing techniques have become a standard therapy for

the treatment of acute on chronic neuromuscular respiratory failure also in the cal care setting [ 26 – 28 , 30 , 36 , 37 ] The increased utilization of NIV has been driven in large part by the need to reduce patient discomfort and to avoid sedation and complications of invasive MV [ 41 ]

In particular, Vianello and colleagues [ 27 ] demonstrated that in the NIV group compared with the invasive MV group, intrahospital mortality (14 % vs 57 %), treatment failure (29 % vs 79 %), and duration of ICU stay (13.6 ± 9.7 vs 47.1 ± 51.9 days) were lower Interestingly, superimposed or unresolved pneumonia with septic shock was absent in individuals receiving nasal intermittent positive pressure ventilation (NIPPV) These complications represented the cause of failure in 6 of the 11 subjects unsuccessfully treated via translaryngeal tube In addition, the results of another prospective cohort study evaluating only NMD patients treated with a noninvasive approach (NIV and MI-E) showed a low mortality rate (8.3 %) and a short hospital stay (12.05 ± 7.03 days) [ 26 ]

Moreover, Servera et al [ 26 ] treated 24 consecutive episodes of ARF in 17 patients with neuromuscular disease using NIV and mechanical coughing aids They showed that noninvasive management was successful in averting death and endotracheal intubation in 79.2 % of the acute episodes

The role of NIV as a reliable alternative to intubation is indirectly supported by two clinical studies conducted in patients with NMDs treated with invasive MV for ARF [ 38 , 42 ] In these studies, the mortality rate was 29 % and 32.8 %, respectively Moreover, Bradley and colleagues [ 38 ] reported a median weaning time period before being discharged to the community of 10 weeks among survivors

Patient selection remains crucial for the success of this ventilatory strategy Bulbar dysfunction increases the patient’s risk for aspiration, hampers the elimina-tion of airway secretions, and increases resistance to airfl ow [ 26 , 41 , 43 ] Therefore,

it can decrease the possibilities of successful use of NIV and MI-E [ 44 ] In addition,

F Racca et al.

32.4.2 Assisted Coughing Techniques

Cough augmentation is a necessary part of the noninvasive respiratory management

of patients with NMD with respiratory insuffi ciency Previous research has strated that cough peak fl ows (CPFs) relate directly to the ability to clear secretions from the respiratory tract The normal CPF in adults exceeds 360 l/min In NMDs, patients with a CPF of >270 l/min are thought to have an adequate cough Studies have demonstrated that a CPF of <160 l/min is associated with diminished cough effectiveness and that cough augmentation is required Patients with a CPF between

demon-160 and 270 l/min have an adequate cough when they are well However, these patients get weaker with the progression of the illness (e.g., upper respiratory tract infections) and CPF can often drop below 160 Therefore, patients with CPF < 270 l/min benefi t from cough-assisted maneuvers during ARF [ 5 47 ]

In patients with acute exacerbation of respiratory failure, techniques to improve airway clearance and MV should always be considered as integrated fi rst-line ther-apy In particular, during acute illness, assisted coughing techniques should be used

in case of (1) oxygen desaturation, (2) increased dyspnea, (3) patient sense of retained secretions, (4) presence of auscultatory rhonchi, and (5) increased ventila-tor peak airway pressure [ 16 , 26 , 28 ]

Effective secretion clearance is crucial for patients with NMD to prevent tasis, pneumonia, and ARF and to reduce hospitalization Thus, in these patients, the use of airway clearance techniques is strongly recommended and should be always included in the noninvasive approach to treat respiratory tract infections [ 23 , 34 ] Mechanical coughing aids include techniques of manually or mechanically assisted coughing

Manual assisted coughing techniques include inspiratory assistance followed by

augmentation of the forced expiratory effort An improvement of the inspiratory capacity can be achieved by a series of tidal breaths without exhalation between

them (i.e., air stacking ), obtained with the application of positive pressure with

self-infl ating bags or mechanical ventilators Forced exhalation is augmented by pushing

on the upper abdomen (i.e., abdominal thrust ) or chest wall (i.e., anterior chest

32 Noninvasive Mechanical Ventilation in Patients with Neuromuscular Disease

Bronchoscopy should be considered only in cases of persistent atelectasis after

all noninvasive airway clearance techniques have proven to be unsuccessful [ 23 ]

32.4.3 Extubation Process

After recovery from the acute illness, patients who do not have severe bulbar ment should be promptly extubated and started immediately on NIV [ 10 , 52 , 53 ] Unfortunately, because of the weakness of the inspiratory muscles, inadequate cough, and inability to handle oropharyngeal secretions, a substantial proportion of patients with NMD who undergo invasive mechanical ventilation fail to pass spon-taneous breathing trials after recovery from the acute illness and are at high risk for extubation failure [ 2 38 , 54 , 55 ] It should be emphasized that extubation failure is

impair-an outcome to be avoided because it is independently associated with increased hospital mortality, prolonged ICU and hospital stay, higher costs, and greater need for care Therefore, strategies preventing this occurrence are required

NMD patients are considered at high risk of extubation failure in the presence of one or more of the following conditions:

• Ineffective cough, defi ned as peak cough expiratory fl ow less than 160 l/min

• Hypercapnia during spontaneous breathing trials

• History of extubation failure

• Failed multiple spontaneous breathing trials

Early application of NIV combined with cough-assist techniques can increase the possibility of successful extubation in these patients Vianello et al [ 56 ] demon-strated that patients with NMDs who received NIV combined with assisted cough were less likely to require reintubation and tracheotomy compared with historical controls who had received standard medical treatment consisting in supplemental oxygen and conventional chest physical therapy Moreover, Bach et al [ 52 ] reported

F Racca et al.

the results of a large uncontrolled study performed on a NMD population that also included patients with acquired critical care myopathy, showing that the standard-ized use of NIV and cough assistance leads to successful extubation in almost all cases of NMD patients

Bach et al [ 52 ] developed a NMD-specifi c extubation protocol and NMD- specifi c extubation criteria While intubated, ventilatory support was used to main-tain normocapnia and normal respiratory rates A cough machine was used at −40

to + 40 cmH 2 O or greater with exsuffl ation-timed abdominal thrusts The cough machine sessions were up to every 20 min to maintain or return the pulse oxyhemo-globin saturation (SpO 2 ) to ≥95 % in ambient air Once extubation criteria (Table 32.3 ) were met, the orogastric or nasogastric tube was removed to facilitate post-extubation nasal NIV The patient was then extubated directly to NIV on assist/control on room air NIV was provided via a combination of nasal, oronasal, and mouthpiece interfaces For episodes of SpO 2 < 95 %, ventilator setting, interface air leakage, CO 2 retention, and cough machine were considered The therapists, nurses, and, in particular, the family and personal care attendants provided Mechanical assisted cough via oronasal interfaces up to every 20 min until the SpO 2 no longer dipped below 95 % and the patients felt comfortable and clear of secretions Tracheostomy may be required, but it should not be considered in the acute phase Tracheotomy would be recommended if the extubation criteria (Table 32.3 ) could not be met within 2 weeks of application of the protocol [ 52 ]

Conclusion

In conclusion, when patients with NMDs develop respiratory failure, a sive approach is preferred where feasible For patients who do not have severe bulbar impairment, the use of NIV in combination with assisted coughing is an effective alternative to invasive ventilation Moreover, ARF is usually prompted

noninva-by precipitating factors, whose identifi cation is essential because they are nable to therapy If a noninvasive approach fails, patients can be intubated and mechanically ventilated as a short-term measure After recovery from the acute illness, patients without severe bulbar impairment should be promptly extubated and treated with NIV combined with assisted coughing Finally, tracheotomy can

ame-be considered, but not as an acute intervention

Table 32.3 Extubation criteria for patients with NMD at high risk of extubation failure

Afebrile and normal white blood cells count

PaCO 2 ≤ 40 mmHg at peak inspiratory pressures < 35 cmH 2 O on full-setting assist/control mode

SpO 2 ≥ 95 % for 12 h or more in ambient air

All oxyhemoglobin desaturations <95 % reversed by cough machine and suctioning via

translaryngeal tube

Fully alert and cooperative, receiving no sedative medications

Chest radiograph abnormalities cleared or clearing

Air leakage via upper airway suffi cient for vocalization upon cuff defl ation

SpO 2 pulse oxyhemoglobin saturation

32 Noninvasive Mechanical Ventilation in Patients with Neuromuscular Disease