AIRWAY MANAGEMENT IN EMERGENCIES - PART 3 pot

䉴BMV TIPS AND PEARLS Ideal Head and Neck Positioningfor BMV Ideally, for BMV, the head and upper neckshould be extended23a to attain a more directpath for the delivered volumes from face

Sounds: A number of conditions associated

with abnormal upper and lower airway sounds

may cause difficulty with BMV

A history of snoring has been correlated

with DMV.21As with the obese patient, this may

be associated with redundant oropharyngeal

tissues Early placement of an OPA, and

main-taining a head-extended position will help

Stridor is almost always a sign of

patho-logic airway obstruction and should be

consid-ered an ominous sign Any patient presenting

with inspiratory or expiratory stridor should be

considered as potentially very difficult or

impos-sible to bag-mask ventilate

The patient with “stiff”, poorly compliant

lungs, (often associated with wheezing or rales)

will present increased resistance to bag-mask

ventilation and requires higher than normal

insufflation pressure

The presence of two or more of the factors

presented above significantly increases the

potential for DMV.21The true incidence of DMV

in the emergency department (ED) is not clear

but is likely greater than that seen with the

elective surgical population In the operating

room, DMV has been reported to occur in up

to 5–8% of elective surgical patients.19, 21

Inter-estingly, the DMV rate is twice as high (15.5%)

in patients who were also described as difficult

intubations.19

Prediction of difficulty with BMV is an

important component of the airway assessment,

as BMV remains the “go to” method of gas exchange

both before and between intubation attempts It

also represents a vital decision node in airway

management in two ways:

A Decision making: Anticipated difficulty

with BMV may point to the need for an

awake technique for intubation, especially

if difficulty with laryngoscopy is also

pre-dicted (see Chap 11)

B Defining the failed airway: In the setting

of failed intubation, the inability to maintain

the SaO2 >90% with BMV defines failed

oxygenation, mandating proceeding with

rescue oxygenation via an extraglottic device

or cricothyrotomy (see Chap 12)

One last implication of predicted difficultywith BMV is the automatic need for an addi-tional assistant, assuming a high probability ofrequiring a two-person technique

䉴BMV TIPS AND PEARLS Ideal Head and Neck Positioningfor BMV

Ideally, for BMV, the head and upper neckshould be extended23(a) to attain a more directpath for the delivered volumes from face to tra-chea, (b) to maintain longitudinal tension onthe lumen of the upper airway24 and possibly,(c) to increase retrolingual and retropalatalspace.25 When studied, no additional benefitwas noted with elevation of the occiput (i.e.,the “sniff” position) compared with simple headtilt starting in the neutral position.23

Gastric Insufflation

Protracted periods of BMV or poor technique(e.g., delivering breaths during the expiratoryphase of the patient’s respiratory cycle; notmaintaining an adequately open upper airway;

or using excessive tidal volumes or positivepressure) can lead to insufflation of the esoph-agus and stomach Gastric distention in turnpresents two problems:

• It predisposes to regurgitation of gastric tents, potentially leading to aspiration, withits sequellae

con-• Particularly in children, but also in adults,massive gastric distention can significantlyelevate and interfere with movement of thediaphragm, in turn creating further difficultywith BMV by impacting respiratory systemcompliance In extreme cases, gastric rupturecan occur

Gastric insufflation can be avoided by

care-ful attention to delivered tidal volumes,

employ-ing the lowest ventilation pressures possible

(below 20 cm H2O), and using airway adjuncts

such as the OPA and NPA Evidence is

emerg-ing that especially in the cardiac arrest patient,

lower esophageal sphincter pressure decreases

rapidly from the normal 20 cm H2O to as little

as 5 cm H2O, underscoring the need to

mini-mize applied insufflation pressures.26

Applica-tion of cricoid pressure (see below) can also be

considered Although most patients can be

ade-quately oxygenated and ventilated using good,

well-timed BMV technique, some gastric

insuf-flation is inevitable BMV should therefore be

viewed as a “bridging” procedure to be used for

a limited period of time If clinically significant

gastric distention is suspected, an oro- or

naso-gastric tube should be passed to decompress

the stomach

Cricoid Pressure and BMV

Posterior pressure on the cricoid cartilage

com-presses the esophagus between the

cartilagi-nous ring of the cricoid and the body of the

C6 vertebra It is often used to prevent passive

regurgitation of gastric contents during

rapid-sequence intubation, but can also be

consid-ered in the unconscious patient during BMV to

reduce inadvertent insufflation of air into the

stomach,27as discussed above However, it must

be appreciated that cricoid pressure can cause

difficulty with BMV,28, 29especially if applied at

excessive pressures or in an upward direction.30

If this is suspected, it should be at least

tran-siently released, to determine if that is the cause

of difficulty

“AutoPEEP”

The patient with reactive airways disease

experi-ences air trapping and difficulty with exhalation

In all patients, but particularly those with known

or suspected air trapping disease, attention must

be paid to allowing sufficient time for tion during BMV Failure to do this may result

exhala-in a buildup of exhala-intrathoracic pressure, which exhala-inturn risks both cardiovascular collapse and baro-trauma Pressure may also be alleviated simply

by intermittently releasing the seal made by themask against the face

Cervical Spine Precautionsand BMV

BMV can be performed safely in the patient who

is considered at risk for a cervical spine (C-spine)injury, for example, the unconscious traumapatient However, radiologic studies haveshown that movement of the C-spine with BMV

is as much or more than that occurring withlaryngoscopic endotracheal intubation.31–34 Assuch, during BMV, manual in-line neck stabi-lization (MILNS) should be applied Head tiltshould be omitted: jaw lift is the only airway-opening maneuver that should be used

The Clinician with Small orTiring Hands

A one-person technique may be difficult orimpossible for the clinician with smaller hands,

or a clinician of average stature dealing with avery large patient In such situations, early use of

a two-person technique should be considered

Laryngospasm

Laryngospasm is a tight and complete adduction

of the vocal cords It sometimes occurs in response

to attempted airway manipulation in deeplysedated patients, and may be more common inthe pediatric patient Its effects can be dramatic,with an almost total inability to bag-mask venti-late the patient If this is suspected, application

of CPAP with the BVM device will often helpbreak the spasm: simply continue to apply a tight

seal with the mask, while maintaining light but

continuous positive pressure on the bag Severe

or recalcitrant cases may require a small dose of

skeletal muscle relaxant, for example,

succinyl-choline 20 mg in the adult patient

All clinicians with airway management

respon-sibilities must be able to assess the critically ill

patient for airway patency and adequacy of gas

exchange BLS protocols should be followed to

open the airway, and if needed, positive-pressure

ventilation with BMV instituted BMV must be

learned and practiced, and should not be looked

upon as an easy skill As the clinician becomes

familiar with basic BMV, various adjuncts and

additions to BMV can be used, such as PEEP

and “pop-off” valves, depending on the

prac-tice environment A formal approach should be

applied to the difficult BMV situation, and the

predictors of difficult BMV appreciated Faced

with ongoing difficulty in performing BMV

and/or intubation, the clinician should consider

placing an extraglottic device such as a laryngeal

mask airway or Combitube

REFERENCES

1.Dorges V, Wenzel V, Knacke P, Gerlach K

Com-parison of different airway management strategies

to ventilate apneic, nonpreoxygenated patients.

Crit Care Med 2003;31(3):800–804.

2 Gausche M, Lewis RJ, Stratton SJ, et al Effect of

out-of-hospital pediatric endotracheal intubation

on survival and neurological outcome: a controlled

clinical trial JAMA 9, 2000;283(6):783–790.

3 Stockinger ZT, McSwain NE, Jr Prehospital

endo-tracheal intubation for trauma does not improve

survival over bag-valve-mask ventilation J Trauma.

2004;56(3):531–536.

4 Stapleton ER Basic life support cardiopulmonary

resuscitation Cardiol Clin 2002;20(1):1–12.

5 Martin PD, Cyna AM, Hunter WA, et al Training

nursing staff in airway management for

resuscita-tion A clinical comparison of the facemask and

laryngeal mask Anaesthesia 1993;48(1):33–37.

6 Caples SM, Gay PC Noninvasive positive pressure ventilation in the intensive care unit: a concise

review Crit Care Med 2005;33(11):2651–2658.

7 Masip J, Roque M, Sanchez B, et al Noninvasive ventilation in acute cardiogenic pulmonary edema: systematic review and meta-analysis JAMA 2005;294(24):3124–3130.

8 Mehta S, Hill NS Noninvasive ventilation.

Am J Respir Crit Care Med 2001;163(2):540–577.

9 Confalonieri M, Garuti G, Cattaruzza MS, et al A chart

of failure risk for noninvasive ventilation in patients

with COPD exacerbation Eur Respir J 2005;25(2):

348–355.

10 Templier F, Dolveck F, Baer M, et al Laboratory testing measurement of FIO2 delivered by Boussi- gnac CPAP system with an input of 100% oxygen.

Ann Fr Anesth Reanim 2003;22(2):103–107.

11 Gabbott DA, Baskett PJ Management of the airway

and ventilation during resuscitation Br J Anaesth.

1997;79(2):159–171.

12 Levitan R, Ochroch EA Airway management and direct laryngoscopy A review and update.

Crit Care Clin 2000;16(3):373–388.

13 Roberts K, Porter K How do you size a

nasopha-ryngeal airway Resuscitation 2003;56(1):19–23.

14 Stoneham MD The nasopharyngeal airway ment of position by fibreoptic laryngoscopy.

16 Schade K, Borzotta A, Michaels A Intracranial

mal-position of nasopharyngeal airway J Trauma.

2000;49(5):967–968.

17 Part 4: Adult Basic Life Support Circulation.

2005;112(24_suppl):IV19–IV34.

18 Wenzel V, Idris AH, Montgomery WH, et al Rescue

breathing and bag-mask ventilation Ann Emerg Med.

2001;37(4 Suppl):S36–S40.

19 Yildiz TS, Solak M, Toker K The incidence and risk

factors of difficult mask ventilation J Anesth.

2005;19(1):7–11.

20 Davidovic L, LaCovey D, Pitetti RD Comparison of 1-versus 2-person bag-valve-mask techniques for manikin ventilation of infants and children.

Ann Emerg Med 2005;46(1):37–42.

21 Langeron O, Masso E, Huraux C, et al Prediction of

difficult mask ventilation Anesthesiology 2000;92(5):

1229–1236.

22 Walls RM, Murphy M Identification of the

diffi-cult and failed airway In: Walls RM, ed Manual

of Emergency Airway Management 2nd ed.

Philadelphia: Lippincott Willimas and Wilkins;

2004.

23 Morikawa S, Safar P, Decarlo J Influence of the

headjaw position upon upper airway patency.

Anesthesiology 1961;22:265–270.

24 Hillman DR, Platt PR, Eastwood PR The upper

air-way during anaesthesia Br J Anaesth 2003;91(1):

31–39.

25 Isono S, Tanaka A, Ishikawa T, et al Sniffing

posi-tion improves pharyngeal airway patency in

anes-thetized patients with obstructive sleep apnea.

Anesthesiology 2005;103(3):489–494.

26 Gabrielli A, Wenzel V, Layon AJ, et al Lower

esophageal sphincter pressure measurement

dur-ing cardiac arrest in humans: potential implications

for ventilation of the unprotected airway

Anesthe-siology 2005;103(4):897–899.

27 Wenzel V, Idris AH, Dorges V, et al The respiratory

system during resuscitation: a review of the history,

risk of infection during assisted ventilation,

respi-ratory mechanics, and ventilation strategies for

patients with an unprotected airway Resuscitation.

2001;49(2):123–134.

28 Palmer JHM, Ball DR The effect of cricoid pressure

on the cricoid cartilage and vocal cords: an

endo-scopic study in anaesthetised patients sia 2000;55(3):263–268.

Anaesthe-29 Hocking G, Roberts FL, Thew ME Airway

obstruc-tion with cricoid pressure and lateral tilt thesia 2001;56(9):825–828.

Anaes-30 Hartsilver EL, Vanner RG Airway obstruction with

cricoid pressure Anaesthesia 2000;55(3):208–11.

31 Brimacombe J, Keller C, Kunzel KH, et al Cervical spine motion during airway management: a cine- fluoroscopic study of the posteriorly destabilized

third cervical vertebrae in human cadavers Anesth Analg 2000;91(5):1274–1278.

32 Aprahamian C, Thompson BM, Finger WA, et al Experimental cervical spine injury model: evalua- tion of airway management and splinting tech-

niques Ann Emerg Med 1984;13(8):584–587.

33 Donaldson WF 3rd, Heil BV, Donaldson VP, et al The effect of airway maneuvers on the unstable

C1-C2 segment A cadaver study Spine 1997;22(11):

1215–1218.

34 Hauswald M, Sklar DP, Tandberg D, et al Cervical spine movement during airway management: cinefluoroscopic appraisal in human cadavers.

Am J Emerg Med 1991;9(6):535–538.

• To avoid patient morbidity, esophagealintubations must be immediately recognizedand corrected.

䉴INTRODUCTIONThis chapter will review direct laryngoscopy andintubation, including the initial response to

encountered difficulty Direct laryngoscopy (DL)

is so named because it results ideally in direct

line-of-sight visualization of the glottis (Fig 5–1).While DL is only one method of facilitating defin-itive airway management, it is still the proceduralstandard for intubation in emergencies, and assuch is deserving of a detailed discussion Alter-native intubation techniques, including blind naso-tracheal intubation, are discussed in later chapters

䉴PREPARATION FORENDOTRACHEAL INTUBATION

The adage that “your first shot is your best shot”

is very applicable to laryngoscopy and tion Prior to proceeding with any intubation, it

intuba-is essential that the following preparations havebeen undertaken:

䉴KEY POINTS

• Direct laryngoscopy remains the

proce-dural standard for emergency intubation

• The clinician should always

psychologi-cally prepare for a difficult airway, in an

attempt to “anticipate the unanticipated.”

• Special attention must be paid to positioning

the morbidly obese patient to facilitate

direct laryngoscopy

• Cricoid pressure and external laryngeal

manipulation (ELM) are two separate

maneuvers done on two separate structures,

for different purposes

• Failure to engage the hyoepiglottic

liga-ment in the vallecula is a probable cause

of the novice failing to achieve an

ade-quate view during direct laryngoscopy

• Head lift, two-handed laryngoscopy

and ELM represent three ways to use

two hands on the first intubation

attempt (“3–2–1”)

• Beware the “pseudolarynx,” especially in

young children

• A tracheal tube introducer (“bougie”) or

fiberoptic stylet can be used on the first

intubation attempt when “best look” direct

laryngoscopy has failed to yield an

ade-quate view

Copyright © 2008 by The McGraw-Hill Companies, Inc Click here for terms of use

A Equipment should be assembled and

imme-diately available for management of either a

standard or unanticipated very difficult airway

If possible, this equipment should be

pre-pared prior to the patient’s arrival Ideally, a

dedicated airway equipment cart with all

the necessary tools, checked daily, should

be a fixture in most acute-care areas

B The patient and clinician performing the

intubation should be positioned in the

optimal (allowable) position for direct

laryn-goscopy

C The patient has been optimally

preoxy-genated.

D Large-bore intravenous (IV) access has

been obtained and a fluid bolus delivered,

when appropriate

E Drugs needed to facilitate airway

manage-ment are available Care should be taken to

match the drug type and dosage with the

patient and any acute or underlying chronic

conditions

F Personnel: Airway management is not a

one-person job At least one assistant is

nec-essary to help, guided by specific directions

If problems are anticipated, this should becommunicated to the team, and roles assignedbefore getting started

INTUBATION

A well-equipped airway cart is not useful unless

it is at the bedside and its contents are familiar.The following mnemonic may be helpful toensure that essential pieces of equipment are

immediately available: STOP “I” “C” BARS.

Suction—Rigid tonsillar suction is vital, turned

on and placed in close proximity to thepatient’s head If there is a high likelihood

of encountering copious amounts of blood

or regurgitated matter, two running suctionsare not excessive The suction tubing mustFigure 5–1 Direct laryngoscopy is so-named as it affords a direct line-of-sight view from the clinician’s eye to the laryngeal inlet.

be connected to an appropriate wall unit.

The rigid suction catheter should be checked

to see if it has a thumb port that must be

occluded to work effectively

Tubes—An appropriately sized endotracheal

tube (ETT, e.g., adult female 7.0; adult male

8.0 internal diameter, [ID]) is prepared, as

well as a tube a half or full size smaller

Rarely is a larger tube size required in an

adult patient A 10 cc syringe is attached to

the pilot line, and the cuff integrity checked

by fully inflating, then deflating it The ETT

tip can be lubricated with 2% lidocaine jelly

or other water soluble lubricant For all

emer-gency intubations, a lubricated stylet should

be inserted into the ETT If a curved

Mac-intosh blade is used, the stylet curve should

not exceed the default curvature of the ETT

Alternatively, and in particular for a straight

blade, a “straight to cuff” shape will be

ben-eficial, whereby the tube is styletted

straight, with a 25–35° upward bend placed

just proximal to the cuff1(Fig 5–2) For atric patients, the Broselow tape can be con-sulted for appropriate ETT sizing

pedi-Oxygen and positive pressure—A manual

resuscitator with oxygen reservoir bag,attached to high flow O2,should be avail-able As the only source of positive pressureventilation, this device should be checked

by occluding the patient end with a fingerand squeezing the self-inflating bag, feelingfor the positive pressure thus developed.The reservoir bag should be distended

Pharmacology—All the drugs that could

possi-bly be needed should be drawn up and

labeled This may include drugs needed for

topical airway anesthesia, IV sedation, orrapid-sequence intubation (RSI), includinginduction agent and muscle relaxant Thearmamentarium should always include anagent to treat postintubation hypotension—merely instituting positive pressure ventila-tion can interfere with venous return and

Figure 5–2 “Straight to cuff” stylet preparation of the ETT (above) compared to natural curve (below).

cause hypotension, particularly in the

vol-ume-depleted patient

Intravenous access—Good IV access (ideally

18G or larger) should be in situ,

free-flowing and not on a pump It is rare that

a patient will not benefit from a fluid bolus

of 10–20 mL/kg prior to intubation

Connect to monitors and Confirmation—During

intubation, the patient should ideally be

mon-itored with an electrocardiogram (ECG) tracing,

noninvasive blood pressure cuff (cycling at

intervals of no longer than 3 minutes), and a

pulse oximeter In addition, objective means

for confirming tracheal location of the ETT

should be available, for example, capnometry

and/or an esophageal detector device

Blades and Bougie—The laryngoscope should

be checked for bright light intensity

Sev-eral blades should be available The #3

Mac-intosh (curved) blade will be useful as a

default blade, with the #4 for larger males

To those familiar with it, a straight blade

(e.g., Miller, Phillips, or Wisconsin) can be

a useful primary or alternative blade A

tra-cheal tube introducer (bougie) should be

within easy reach during all emergency

intu-bation attempts

Alternative intubation device—In addition to

the bougie, during every emergency

intuba-tion attempt, equipment for an alternative

intubation technique should be available for

immediate use Examples include the LMA

FastrachTM

(Intubating Laryngeal Mask

Air-way [ILMA]), fiberoptic optical stylet, or

Tra-chlight These devices all require

prepara-tion by someone familiar with their use If

the patient is being bag-mask ventilated

with difficulty in between intubation

attempts, the primary clinician will not be

available to prepare this equipment

Rescue oxygenation technique—A Laryngeal

Mask Airway (e.g., LMA ClassicTM

, ProSeal,Supreme, or Fastrach), Combitube, or other

extraglottic device is useful as a rescue

oxy-genation tool One such device should be

sized for the patient and within arm’s reach

for the infrequent failed intubation or failedoxygenation (Chap 12) situation

Surgical (i.e., cricothyrotomy) technique—For

most intubations, simply knowing the ment’s location and how to use it is adequatepreparation However, for anticipated verydifficult situations, it may be appropriate tohave this equipment out and opened: a com-ponent of the so-called “double set-up”

equip-䉴POSITIONING FORLARYNGOSCOPY ANDINTUBATION

The clinician should be optimally positionedbefore an intubation attempt, as should the patient

Clinician Positioning

Comparisons of the posture of experienced andnovice laryngoscopists have observed the fol-lowing: experienced clinicians stand furtherback, with straighter backs and arms,2and holdthe laryngoscope closer to the base of theblade3(Fig 5–3) During direct laryngoscopy,the laryngoscopist’s arm should be only mod-estly flexed at the elbow and adducted, and notbent at right angles and abducted Better mechan-ical advantage is then developed by the applica-tion of a more in-line axial force through the arm

to the handle of the laryngoscope Once a view

of the laryngeal inlet is obtained, some clinicianselect to keep the arm adducted against the trunkfor additional support This position of the arm isconsistent with the optimal distance from thelaryngoscopist’s eye to the patient’s glottis ofapproximately 16–18 inches Attention to clinicianpositioning may help deliver favorable mechanicaland visual advantage during laryngoscopy

Patient Positioning

Three aspects of patient positioning are crucial.Failure to observe these positioning principlesmay make obtaining a good view at laryn-goscopy more difficult

A “Up-down,” referring to stretcher height.

Often overlooked, the patient should be at the

appropriate height—with the middle of the

patient’s head at the level of the clinician’s belt

buckle

B “North-south”: the patient’s head should

be positioned as close as possible to theupper (“north”) end of the stretcher

C “Sniff,” that is, head and neck positioning.

Classic teaching suggests placing the headFigure 5–3 Clinician positioning during direct laryngoscopy: relatively straight back; modestly flexed, adducted elbow, and a grip on the laryngoscope handle close to the blade.

and neck in the “sniffing” position for direct

laryngoscopy When not contraindicated by

C-spine precautions, this involves flexing

the neck at the cervico-thoracic junction,

with extension of the neck at the upper few

cervical vertebrae and head at the

occipito-cervical junction This will help align airway

axes, in turn helping attain a direct

line-of-sight view from the clinician’s eye to the

laryn-geal inlet (Fig 3–8, Chap 3) The sniffing

position can be attained by placing folded

blankets (about 4”/8 cm high) under the

patient’s occiput and/or lifting the head ing laryngoscopy, using the right hand underthe occiput

dur-The axis alignment sought by placing thepatient in the sniffing position can be exter-nally referenced Observing the patient fromthe side, when the external auditory meatus islined up horizontally with the sternal notch, thepatient is generally well positioned for laryn-goscopy in a good “sniff” position (Figs 5–4 Aand B) This same “ear-to-sternum” positioning

Figures 5–4 In contrast to the positioning of the patient in the neutral position (A), a line drawn from the external auditory meatus to the patient’s sternum (“ear to sternum” line) will give a rough indication of good positioning for direct laryngoscopy (B).

A

B

is also key to positioning the morbidly obese

patient4(see next section) While some recent

publications have suggested that

cervicotho-racic flexion is not a necessary component of

optimal positioning for laryngoscopy,5–7other

studies challenge this contention by

suggest-ing the utility of a head lift8,9in improving

laryn-geal view

䉴POSITIONING IN SPECIAL

SITUATIONS

C-Spine Precautions

In the patient requiring C-spine precautions,

the sniff position is not an option DL under

these conditions will be more difficult, with an

expected incidence of blind, Grade 3 views

(no part of the glottis visible) of 20%–25%10

with application of manual in-line neck

stabi-lization (MILNS) The incidence of Grade 3

views increases to 50% or more10, 11with a

cer-vical collar applied For this reason, during

attempts at laryngoscopy and intubation,

MILNS should be substituted for the cervical

collar, as the latter increases difficulty by also

interfering with mouth opening Note that the

function of in-line stabilization is as a reminder

to the laryngoscopist to minimize movement,

not necessarily to preclude any movement

whatsoever

Morbid Obesity

Airway management in the morbidly obesepatient can be difficult in terms of bag-mask ven-tilation (BMV), laryngoscopy and intubation, aswell as cricothyrotomy In this population, unlessthe patient is well positioned, during laryn-goscopy, the handle of the laryngoscope mayabut the chest wall Specially made short handlescan be used in this situation but are usually unnec-essary when the patient is properly positioned.Such positioning can be attained by building aramp with folded blankets (Fig 5–5) Five to sevenfolded blankets are placed under the occiput, 3–5under the shoulders, and 1–3 under the scapulae.This will elevate the face above the chest walland eliminate the concern of the handle hittingthe chest During “ramping,” the unsupportedarms are allowed to fall to the side, taking withthem additional soft tissue from the anterior chest.These benefits cannot be accomplished bysimply raising the head of the bed, nor by just lift-ing the head of the obese patient at laryngoscopy.Ramping is required in the morbidly obese patient

to achieve the previously mentioned “ear tosternum” positioning4(Fig 5–6 A and B)

Tipping the gravid uterus to the left will help

avoid compression of the aorta and inferior

vena cava, which can otherwise cause supine

hypotension syndrome There is also a higher

incidence of difficult laryngoscopy and

intu-bation in the obstetrical population,12 and

pregnant patients in the second and thirdtrimesters should be considered at high risk forpassive regurgitation

Both morbidly obese and third trimesterpregnant patients have a limited functionalresidual capacity, and can be expected to

Figure 5–6 A morbidly obese patient (A) before and (B) after positioning on a “ramp” of folded blankets Note the “ear-sternum” line before and after

A

B

desaturate quickly when rendered apneic, for

example, during an RSI

The Patient in Extreme Respiratory

Distress

The acutely dyspneic patient will not tolerate

the supine position If an awake intubation is

planned, the patient can be intubated in the ting or semisitting position using DL or otherintubation technique In this situation, the clin-ician may need to be positioned on a chair atthe patient’s head (Fig 5–7) If an RSI is planned,the patient will need to be in the sitting positionuntil loss of consciousness occurs with theinduction agent

sit-Figure 5–7 Sitting position direct laryngoscopy Note laryngoscopist initially guiding laryngoscope blade with fingers of right hand.

The Pediatric Patient

The neonate, with its large head and occiput

relative to the thorax, will often end up with the

neck excessively flexed, if placed supine on a

table This is the one situation in which a folded

towel may need to be placed under the

shoul-ders, to decrease lower C-spine flexion to the

same degree that is needed in the adult The

toddler and young child (to approximately

age six) will be well-positioned merely placed

with the head flat on a table Above age six,

positioning with the usual towel or folded

blanket under the occiput will be needed

During the preparation phase, the patient

should receive as close to 100% O2as possible

Holding a manual resuscitator (supplying O2

at 15 L/min, with a functioning O2 reservoir

system) firmly on the face is ideal If the

patient’s spontaneous ventilations are felt to

be inadequate, timed inspiratory assisted

ven-tilation may be required Obviously, in the

apneic patient, positive pressure ventilation

will be needed Preoxygenation is a vitally

important step Unintentionally

omit-ting this step puts the patient at risk of

profound hypoxemia during attempted

intubation.

Laryngoscopes and Blades

The laryngoscope used for DL consists of a blade

and handle: the handle houses the power supply

and sometimes the light source Generally the

laryngoscope blade snaps on to the top of a

handle Rotating the blade to a position 90° to

the handle activates the illumination supply,

which is delivered toward the tip of the blade

Some blades have a distal bulb-on-blade design,

while others transmit light from a bulb located

in the handle to the blade tip via a fiberopticbundle A fiberoptic laryngoscope with arechargeable battery system is likely the mostdependable and has the potential to provide thebrightest lighting Blades can be reusable or dis-posable Disposable blades are made of plastic

or steel As the most important piece of tion equipment, the laryngoscope should be ofreliable quality

intuba-Familiar to many clinicians, the Macintosh

blade (Fig 5–8) is curved, designed to partiallyconform to the shape of the tongue It is mostoften used by placing the blade tip in the val-lecula, at the junction of the base of the tongueand origin of the epiglottis As the blade tip ispressed into this space and lifted, pressure onthe hyoepiglottic ligament will help indirectlylift the epiglottis anteriorly, exposing theunderlying glottic opening A size 3 Macintoshblade will be appropriate in the majority ofadult patients, although in larger patients, espe-cially those with long necks, a Macintosh 4 blademay be needed Also note that curved bladescan be used to directly “pick up” or elevate theepiglottis

Straight laryngoscope blades (Fig 5–9) such

as the Miller, Phillips, or Wisconsin are

designed primarily to displace the tongue tothe left and directly elevate the epiglottis, thusexposing the vocal cords Often used as theblades of choice in pediatric patients, they canalso be useful in the adult patient with an “ante-rior” larynx, small mandible, large tongue, orprominent central incisors.13 Many straight

blade aficionados prefer its use by a glossal approach, whereby the blade is placed

para-alongside the tongue, on its right Thisapproach has been shown to be effective insome situations where curved blade laryn-goscopy had failed.14

Finally, specialty blades exist to help in

dif-ficult situations The McCoy blade, also known

as the levering tip or CLM McCoy) blade, has the basic shape of the

(Corazelli-London-Macintosh, but in addition, features a levering

distal tip When an activating lever is depressed

toward the laryngoscope handle (Figs 5–10 A

and B), the blade tip levers upward, helping

to elevate the epiglottis (Figs 5–11 A and B)

The literature suggests it may be useful inconverting Grade 3 views to 2 or better, par-ticularly when caused by applied manual in-linestabilization.15–18

Figure 5–8 Macintosh size 3 and 4 (adult) curved blades.

Figure 5–9 From left to right, Wisconsin, Phillips, and Miller straight blades

Figure 5–10 A, B The McCoy (CLM) blade, (A) in the neutral and (B) partially activated positions.

Figure 5–11 Fluoroscopic images of the McCoy blade (A) before and (B) after partial blade tip activation (the arrow in both images points to the epiglottis)