Critical Care Obstetrics part 13 pdf

Assisted v entilation If an infant is not breathing, is breathing but incapable of sustain-ing a heart rate of above 100, or is in signifi cant respiratory dis-tress and requiring supp

an increase in pulmonary vascular resistance For the neonate, without connection to the placenta after the cord is clamped, maintenance of the fetal circulation shunts blood away from the lungs, the only available organ of gas exchange

In the circumstances of progressive asphyxia, the fetus or newborn responds with an increase in systemic vascular resis-tance or vasoconstriction This decreases blood fl ow to the mus-culature and the intestines, while attempting to increase blood

fl ow to the head and heart Thus, blood fl ow to the cardiac and cerebral vessels is maximized at the expense of “ non - vital ” organs This pattern of blood fl ow, if prolonged, results in an increasing acidosis [4,5] The increasing acidosis along with the hypoxia further increases the pulmonary vascular resistance, exacerbating the problem (Figure 8.2 ) For both fetus and newborn, cardiac output and blood pressure are maintained to the vital organs initially, but will, in the face of increased hypoxia and acidosis fail, as the myocardium fails [6]

Primary and s econdary a pnea

Superimposed on these circulatory and hemodynamic changes is

a characteristic respiratory pattern response to asphyxia The fetus or neonate will initiate gasping respirations (which may

occur in utero ) and, should the asphyxia persist, enter an apneic

phase known as primary apnea If the asphyxia continues, the primary apnea will be followed by a period of irregular gasping respirations Continued asphyxia will lead to a period of unremit-ting apnea known as secondary apnea Figure 8.3 illustrates the respiratory and cardiovascular effects of asphyxia

If an infant is in primary apnea and exposed to oxygen when gasping respirations ensue, exposure to oxygen may be suffi cient

fetal, may occur at the time of delivery or signifi cantly before the

events of parturition It is important to note that intrauterine

ischemic events, even those quite remote from the delivery of the

infant, may extend into the newborn period resulting in a

com-promised infant

Response to h ypoxia

In the normal fetal circulation, blood returning to the heart from

the body and placenta is primarily shunted through the foramen

ovale to the left side of the heart facilitating oxygenated blood to

going to the head and the heart Blood that reaches the right

ventricle is shunted through the ductus arteriosus to the aorta,

bypassing the lungs as a result of a high pulmonary vascular

resistance [3] This serves the fetus well as the major organ of gas

exchange is the placenta (Figure 8.1 )

However, if the fetus or newborn is subjected to “ hypoxic ”

conditions the physiologic response is to exacerbate or maintain

Figure 8.1 Fetal circulation (Reproduced by permission from Faranoff AA,

Martin RJ, eds Neonatal - Perinatal Medicine: Diseases of the Fetus and Newborn ,

7th edn St Louis: Mosby, 2002: 417.)

Figure 8.2 Pulmonary vascular resistance (PVR) in the calf (From [3] )

It is very important to understand that asphyxia may begin in utero The infant may go through primary apnea in utero and be

born in secondary apnea Thus, it is extremely diffi cult to assess the degree of asphyxia at the time of birth For this reason, the resuscitative efforts should begin immediately for all infants born with any degree of depression To wait may only subject the infant to a potentially prolonged resuscitation and an increased risk of neonatal brain damage

Use of the Apgar s core

The Apgar score, which is not routinely given until 1 minute of

age, should not be used to guide decisions regarding resuscitation

interventions If an infant is born in secondary apnea interven-tion should be initiated immediately rather than waiting until 1 minute The Apgar score is intended to provide a “ snapshot ” look

at the condition of the infant at any one moment in time – it is not to be used as a guide for initiating resuscitation

Elements of a r esuscitation Overview (Figure 8.5 )

The ability to provide for a prompt and effective resuscitation should be available for all infants regardless of the relative risk for resuscitation as estimated by prenatal complications, fetal heart tracings or complications of labor For infants who are known to be at high risk of being born depressed, based upon the clinical circumstances, the need for resuscitation should be anticipated and prepared for before the moment of delivery

After delivery, a quick assessment allows for appropriate triag-ing of the infant If the infant is term, breathtriag-ing or crytriag-ing, with good muscle tone and clear amniotic fl uid there is no further need for resuscitation and the infant may be handed to an eager mother The infant who is preterm, and who has any diffi culty with breathing, reduced muscle tone or stained amniotic fl uid should be placed on a preheated radiant warmer for further evaluation

If the neonate is placed on a radiant warmer, the initial steps include drying and warming, correct airway positioning, clearing the airway by suctioning of the mouth and nose, and assessment

of respiratory effort, heart rate and color This should occur within the fi rst few seconds of life and is independent of the

1 - minute Apgar score Subsequent efforts are dictated by assess-ment of respiratory effort, heart rate and color

Gasping or apnea, or a heart rate below 100, should prompt initiation of assisted ventilation Most infants will respond to assisted ventilation alone In an infant with persistent central cyanosis but adequate spontaneous respirations and a heart rate greater than 100 beats per minute, free - fl ow oxygen may be all that is necessary

While the long - term effects of asphyxia are sometimes unavoid-able, a prompt and effective resuscitation will in most cases, restore spontaneous respiratory effort and reverse the hypoxia,

to reverse the process However, once the infant reaches

second-ary apnea, positive - pressure ventilation is required to initiate

spontaneous ventilation Furthermore, the longer the duration of

secondary apnea, the longer it will take for spontaneous

respiratory effort to return following the administration of positive

pressure ventilation (Figure 8.4 ) [7,8]

Figure 8.3 Heart rate and blood pressure changes during apnea (Reproduced

by permission from Textbook of Neonatal Resuscitation , 4th edn Elk Grove, IL:

American Academy of Pediatrics/American Heart Association, 2000: 1 – 7.)

10

20

30

Duration of asphyxia (min)gasp

Last

To first gasp

Time to breathing

Figure 8.4 Time from ventilation to fi rst gasp and to rhythmic breathing in

newborn monkeys asphyxiated for 10, 12.5, and 15 minutes at 30 ° C (From

Adamsons K et al Resuscitation by positive pressure ventilation and tris

hydroxymethyl - aminomethane of rhesus monkeys asphixiated at birth J Pediatr

1964; 65: 807.)

fact that in those infants with persistent neonatal depression, 75% were believed to be due to ineffective or improper ventilatory support Thus, if adequate ventilation is established, in less than one - tenth of 1% is there any need to progress onto chest com-pression or medications

Preparation for a r esuscitation Anticipation

It must be assumed that the infant delivered of a mother requir-ing critical care to support and maintain a pregnancy may require resuscitation Thus, preparation is the fi rst step to assure neonatal resuscitation A careful review of the antepartum and peripartum maternal history, as well as careful assessment of the infant ’ s response to labor, will frequently identify the potential for the delivery of a depressed infant (Box 8.2 ) This review will help assure that the resuscitative team is less likely to be caught unpre-pared or surprised by an infant born in a high - risk situation who requires immediate resuscitation If the infant is vigorous and

ischemia, hypercapnia and acidosis and minimize the long - term

consequences to the child (Box 8.1 )

In those very few infants who do not respond to ventilation,

chest compressions and, possibly, medications may be needed

However, before chest compressions or medications are given, it

must be assured that the infant is being provided with

appropri-ate positive - pressure ventilation

The resuscitative steps for infants with special circumstances

such as thick meconium - stained amniotic fl uid, pneumothorax,

congenital diaphragmatic hernia or erythroblastosis/hydrops will

be discussed later in this chapter

Importance of e stablishing v entilation

In the vast majority of resuscitations, the initiation of effective

positive - pressure ventilation alone will restore spontaneous

res-pirations and heart rate In an exceedingly important and often

overlooked paper, Pearlman et al reported on a large series of

over 30 000 deliveries [9] In their experience only 0.12% of

infants required chest compressions or medication Of note is the

Eval HR Eval

HR

Birth

Clear amniotic fluid?

breathing or crying?

Good muscle tone?

Term gestation?

Routine Care

• Warmth

• Clear airway

• Dry

• Assess color

(may go to mother)

Place under radiant heater (Suction trachea - if meconium guidelines anpply)

Dry thoroughly Remove wet linen Position

Suction mouth, then nose Provide tactile stimulation (optional)

Below 60

Continue PPV

Initiate chest

compressions

Provide oxygen

Above 60 Continue PPV Watch for spontaneous ventilation

Then, discontinue PPV

if HR above 100

Initiate medication if HR below 60 after 30 seconds

of PPV with 100% oxygen and chest compressions

Observe and monitor

Provide oxygen

Evaluate color

No

PPV

? with oxygen

None or gasping

Pink or peripheral cyanosis

Spontaneous

Above 100

Cyanotic

Yes

Evaluate respirations

Figure 8.5 Overview of resuscitation in the delivery room HR, heart rate; PPV, positive - pressure ventilation (Modifi ed from Textbook of Neonatal Resuscitation , 4th edn; Elk Grove, IL; American Academy of Pediatrics/American Heart Association, 2000 Originally published in Faranoff AA, Martin RJ, eds Neonatal - Perinatal Medicine: Diseases of the Fetus and Newborn , 7th edn St Louis: Mosby, 2002: 434.)

Adequate p ersonnel

Individuals vested with the responsibility of resuscitating infants should be adequately trained, readily available and capable of working together as a team Adequate training involves more than simple completion of a certifi cation course on the resuscita-tion of the newborn infant The Neonatal Resuscitaresuscita-tion Program

of the American Heart Association/American Academy of Pediatrics and similar courses serve simply as starting points They do not qualify one to assume independent responsibility in the delivery room Those having completed a course, but still lacking the expertise gained through experience must be ade-quately supervised and supported by experienced personnel Ultimately, the ability to resuscitate neonates is not determined

by professional designation or course completion, but by experi-ence and expertise

Finally, those responsible for resuscitating an infant must be capable of working together as a team If individuals are aware of and able to fulfi ll their respective responsibilities as well as antici-pate the needs of other team members, the tension inherent in a diffi cult resuscitation will be reduced In those institutions where resuscitations are uncommon events, frequent mock code drills will help to maintain skills and develop coordination among team members

Initial s teps and e valuation

To i ts m other or n ot?

Most infants are vigorous, cry upon birth and breathe easily thereafter The decision to bypass resuscitative efforts should, however, be based on data collected during a brief triage of the infant The infant born at term without obvious deformity or the

passage of meconium in utero , who immediately after birth is

vigorous, is breathing easily and who exhibits good tone, may be triaged to its mother if those are the wishes of the parents A light blanket and some drying of the infant by the mother and delivery room staff will help to establish an appropriate thermal environ-ment but should not hinder frequent and adequate assessenviron-ments

of the neonate ’ s condition

If, however, the infant is premature, has passed meconium in utero or exhibits any degree of respiratory distress, hypotonia, or

obvious malformations, the infant should be placed onto a radiant warmer for the initial steps of resuscitation There a more thorough assessment can be performed and possible further resuscitative interventions begun

Initial s teps

Thermal m anagement

Temperatures in delivery rooms are typically lower than the neutral thermal environment for neonates This can leave the newly delivered, wet infant at risk for cold stress Immediately after birth, the infant with any degree of compromise, or for whom there is any concern, should be placed in the microenvi-ronment of a preheated radiant warmer The infant should be thoroughly dried with all wet blankets removed to reduce evaporative heat loss These simple measures can minimize the signifi

Box 8.1 Consequences of asphyxia

Central nervous system

Cerebral hemorrhage

Cerebral edema

Hypoxic - ischemic encephalopathy

Seizures

Lung

Delayed onset of respiration

Respiratory distress syndrome

Meconium aspiration syndrome

Cardiovascular system

Myocardial failure

Papillary muscle necrosis

Persistent fetal circulation

Renal system

Cortico/tubular/medullary necrosis

Gastrointestinal tract

Necrotizing enterocolitis

Blood

Disseminated intravascular coagulation

(From Faranoff AA, Martin, RJ, eds Neonatal - Perinatal Medicine:

Diseases of the Fetus and Newborn , 7th edn St Louis: Mosby, 2002:

420.)

pink despite its high - risk situation, it will be only a pleasant

sur-prise to those preparing for resuscitation

Traditionally, a cesarean delivery of any type has been

consid-ered high risk Enough information is now available to state that

the uncomplicated repeat cesarean section carries no greater risk

for the infant than a vaginal delivery [10]

Anticipation of the potential need for resuscitation has been

made easier by technologic advances allowing better prenatal

assessment of the fetus But, not all events compromising an

infant ’ s response to labor may be predicted For this reason,

equipment and personnel must be immediately available to

inter-vene on behalf of the infant requiring an unanticipated

resuscitation

Equipment

Whenever an infant is delivered, appropriate equipment must be

close at hand and in good working order Having the correct

equipment and skilled individuals to establish adequate

ventila-tion is imperative It is unacceptable for a team member to have

to leave the delivery room in order to retrieve an essential piece

of equipment

cant drop in infant core body temperature experienced

immediately after birth [11] This is particularly important for

the infant with any degree of compromise Hypoxia reduces the

infant ’ s homeostatic response to cold stress, and without

inter-vention, the hypoxic infant will undergo a greater than normal

drop in core body temperature [12] Hypothermia also reduces

the clearance of metabolic acidosis and thus prolongs the

recov-ery from perinatal asphyxia [13]

The premature and/or small infant represents an especially

diffi cult problem from the aspect of temperature control As a

result of the lack of subcutaneous tissue and thin skin they tend

to have greater evaporative water loss across the skin than a term

infant In addition, the large surface area to body mass ratio also

facilitates heat loss and a decrease in body temperature

There are three things that can be done to help diminish heat

loss in the preterm/small infant The fi rst two should be done

before the anticipated delivery: (i) increase the temperature of the

Box 8.2 Factors associated with neonatal depression and asphyxia

Pregnancy - induced hypertension Forceps or vacuum - assisted delivery

Chronic hypertension Breech or other abnormal presentation

Neurologic Prolonged rupture of membranes ( > 18 hours before delivery)

Fetal anemia or isoimmunization Persistent fetal bradycardia

Previous fetal or neonatal death Non - reassuring fetal heart rate patterns

Bleeding in second or third trimester Use of general anesthesia

Premature rupture of membranes Prolapsed cord

Size – dates discrepancy Signifi cant intrapartum bleeding

Fetal hydrops

(Modifi ed from Textbook of Neonatal Resuscitation , 4th edn; Elk Grove, IL; American Academy of Pediatrics/American Heart Association, 2000 Originally published in Faranoff AA, Martin RJ, eds Neonatal - Perinatal Medicine: Diseases of the Fetus and Newborn , 7th edn St Louis: Mosby, 2002:

420.)

delivery room and (ii) make sure that the radiant warmer is pre-heated before the birth of the infant Finally, for infants less than

28 weeks, it is now recommended that consideration be given to placing the infant in a standard, food - quality 1 - gallon polyethyl-ene bag that can easily be obtained from a grocery store A hole

is cut in the closed end of the bag and the bag slipped over the baby with his or her head coming out of the hole The “ zipper ” end can then be closed (Figure 8.6 ) This allows a resuscitation

to proceed with minimal evaporative heat loss and full visualiza-tion of the infant The infant can be placed in the bag in place of,

or after, drying A preheated transport incubator can be used to help maintain body temperature during transport to the nursery

or NICU

Clearing the a irway

The airway is normally cleared with the use of a bulb syringe or suction catheter The mouth is suctioned fi rst and then the nose

It is now clear that at about 1 minute, following an uncompli-cated birth, most infants breathing room air will only attain an oxygen saturation of around 60 – 70% By 5 minutes, most infants have reached ranges in the mid - to high 80% range and, in many infants, it may take 10 minutes to reach oxygen saturations of 90% or higher [15,16] This matter may be complicated by indi-vidual variation in the clinical assessment of color during the transition of a neonate

In the breathing infant with a heart rate of above 100 who appears cyanotic, the use of a pulse oximeter may be of some value Using the newer pulse oximetry models with placement of the oximeter probe on the right hand (preductal), it should be possible to obtain an S p O 2 reading by a couple of minutes of age

in most infants If the S p O 2 is less than 85% then blended oxygen can be provided to whatever extent is necessary to raise the S p O 2

to between 85% to 90%, or until it is quite clear that additional oxygen makes no difference in the oxygen saturations, in which case the infant is likely to have cyanotic congenital heart disease Having said this, it is important to understand that we do not know what the optimal oxygen saturation of a transitioning newborn is at any point in time Thus, the best we can do is to have oxygen blenders and pulse oximeters in delivery units that deal with high - risk infants in order to provide some guidance so that the supplemental oxygen can be provided at the levels which are no higher than necessary If the infant is in need of supple-mental oxygen, it seems prudent to start at about 40% and move

up or down as indicated

Free - fl ow oxygen in high concentrations can easily be admin-istered by oxygen mask (with escape holes) or by cupping the hand around the end of the oxygen tubing and holding this close

to the infant ’ s nose and mouth A fl ow - infl ating (anesthesia) bag and mask or a mask on the end of a T - tube device (such as the Neopuff ® ) held lightly over the infant ’ s nose and mouth may also deliver a measured concentration of inspired oxygen Caution should be used to avoid a seal of the mask to the face so as to avoid providing positive pressure to the lung A self - infl ating bag

is not capable of providing free - fl ow oxygen Cold, dry oxygen can be given in an emergency; however, a persistent need for free - fl ow oxygen should prompt humidifi cation and heating of the oxygen

Assisted v entilation

If an infant is not breathing, is breathing but incapable of sustain-ing a heart rate of above 100, or is in signifi cant respiratory dis-tress and requiring supplemental oxygen, some form of assisted ventilation may be necessary This may be simply the provision

of a continuous positive end - expiratory pressure to a spontane-ously breathing infant or intermittent mandatory positive - pres-sure ventilation with end - expiratory prespres-sure to infants who are not breathing or are in signifi cant respiratory distress

When resuscitating a newborn, one must establish a functional residual capacity (FRC) and provide tidal volumes breaths In the past when positive - pressure ventilation was used the concerns were to provide a peak inspiratory pressure capable of effecting

This is done to fi rst clear secretions in the mouth and potentially

prevent their aspiration should deep breaths occur with nasal

suctioning Gentle suctioning of the mouth will avoid the refl ex

bradycardia associated with stimulation of the posterior pharynx

[14] The infant exposed to meconium in utero represents a

special case and will be discussed later

Tactile s timulation

Drying and suctioning are generally suffi cient to stimulate

respi-rations in the newborn infant Other methods such as fl icking the

feet or rubbing the back have been traditionally used to stimulate

a more vigorous respiratory response If there is no immediate

response to these supplemental methods, positive - pressure

ven-tilation should be promptly initiated Continued tactile

stimula-tion in an unresponsive infant will not succeed and may prolong

the asphyxial process If, after suctioning and tactile stimulation

an infant exhibits apnea or a heart rate of ≥ 100 beats/min,

posi-tive - pressure ventilation should be initiated

Free - fl ow o xygen

The use of oxygen has become a topic which has been subject to

a great deal of discussion and, in some sense, controversy This

is related to the potentially harmful effects of hyperoxia,

espe-cially in an asphyxiated infant As prolonged hypoxia is to be

avoided, it is also necessary to avoid hypoxemia Most of what

has been written involves the role of oxygen in infants who are

in need of active resuscitation with ventilatory support, which we

will discuss later in this chapter However, in the infant who is

breathing spontaneously with no or minimal signifi cant signs of

respiratory distress and whose heart rate is above 100, yet who

remains cyanotic, there is general agreement that there is a need

for supplemental oxygen However, when to introduce the oxygen

and at what levels to start are not well agreed upon

Figure 8.6 Use of plastic bag for reducing evaporative heat loss (Reproduced

from Textbook of Neonatal Resuscitation , 5th edn Elk Grove, IL: American

Academy of Pediatrics/American Heart Association, 2006: 8 – 6.)

appropriate tidal volume is very limited We have neither the knowledge nor the tools to assure appropriate tidal volumes in the immediate newborn lung during resuscitation

How then do we approach a positive - pressure infl ation? Where

in the past we looked for a “ easy rise and fall of the chest ” or provided enough positive pressure to reach certain pressure values, now it is recommended that just enough pressure be pro-vided to improve the heart rate, color and muscle tone These signs are considered the best indicators that infl ation pressures are adequate If these signs are not improving, then one should look for the presence of chest movement and increase the pres-sure, assuming that one has a good face - mask seal [22] Keep in mind that in order to establish an FRC, it may be necessary to use higher pressures and longer inspiratory times for the fi rst few breaths than for subsequent breaths

Positive e nd - e xpiratory p ressure ( PEEP )

We are concerned with not only the degree of inspiration but also the expiratory wing of the breath In surfactant - defi cient animals, ventilation without end - expiratory pressure may result in col-lapse of the distal units of the lung Repeated re - expansion of units of the lung that are allowed to become atelectatic at end expiration leads to shear stresses on the lung that results in similar consequences as those induced by overexpansion of the lung When surfactant - defi cient rabbit lungs are allowed to attain low end - expiratory volumes they have reduced compliance and greater histologic lung injury than those lungs ventilated at a higher end - expiratory volume maintained with end - expiratory pressures [23] When rat lungs are ventilated with a low end expiratory lung volume there is increased cytokine release [24] and increased pulmonary edema [25] It has also been shown that when saline - lavaged rabbit lungs or preterm lambs are ventilated

at low lung volumes there is an impaired response to surfactant

On the other hand, there is also evidence that if preterm lamb lungs are held open at end - expiration with positive end - expira-tory pressure, surfactant function is preserved [26,27] For a very long time we have used end - expiratory pressure with all infants who are on ventilators

Thus, in addition to avoiding overexpansion of the lung, it also may be important to resuscitate infants, especially the pre-mature infant, using an end - expiratory pressure This may help avoid the potential damage which can result from repeated

re - opening of lung units that are allowed to become atelectatic

at end - expiration

Now, many neonatologists routinely use an end - expiratory pressure when they resuscitate an infant with positive - pressure ventilation to prevent the lung from collapsing at end - expiration with the induction of shear stress upon the subsequent infl ation

Continuous p ositive a irway p ressure ( CPAP )

End - expiratory pressure, in the form of mask CPAP, is becoming more and more frequently used in the delivery room with infants who are spontaneously breathing yet have some degree of

chest movement that resembled an “ easy breath ” In recent years

we have taken into consideration the potential lung damage that

can come from over - infl ation that may occur if chest movement

is the only indicator of adequate ventilation We have also begun

to recognize that there is a potential for damage when the lungs

are allowed to defl ate to an end - expiratory pressure of zero with

the induction of shear stresses upon re - infl ation This has led to

the use of a positive end - expiratory pressure, especially when

ventilating premature infants, whose immature lungs may well

be more susceptible to shear stresses than the term infant [17]

Tidal v olume v entilation

In a resuscitation of a newborn, one has to provide tidal volume

breaths that are suffi cient to promote adequate gas exchange, but

which do not over - distend the lung The parameter most often

used for monitoring adequacy of inspiratory fl ow while bagging

is chest wall movement What is not known is how chest wall

movement relates to appropriate expansion of alveoli and true

tidal volume in the non - uniformly infl ated lung of the neonate,

and especially the premature infant with lung disease It is quite

possible, in fact, even likely, that when chest wall movement is

used as a guide for positive - pressure ventilation in the delivery

room we are overdistending more compliant portions of the lung

in our quest for chest rise This is especially problematic in the

immature, surfactant - defi cient lung which may be subject to

non - uniform expansion In these circumstances positive -

pres-sure inspiratory gas may be forced into those areas that are more

compliant, overdistending those areas of the lung

These issues become important to consider as we now realize

that overdistention of the alveoli can induce lung damage There

is good evidence that overdistention of the lung (volutrauma) is

of greater concern than trauma caused by high pressure

(baro-trauma) [18]

Wada et al demonstrated that in preterm lambs ventilated for

30 minutes at high tidal volumes, compared to controls, there was

a decrease in compliance, lower ventilatory effi ciencies and a

decreased subsequent response to surfactant [19] Bjorklund

et al showed that only six large breaths delivered with manual

ventilation immediately after birth created enough injury in the

lung to result in an attenuated response to surfactant, greater

diffi culty in ventilating the animal and more widespread lung

injury in histologic sections [20]

Overdistention of the lung can induce a series of events that

lead to lung injury, e.g interstitial and alveolar edema, as well as

the initiation of an infl ammatory response by attraction and

acti-vation of neutrophils and macrophages Simply stretching the

lung opens stretch - activated ion channels and increases epithelial

and endothelial permeability It can also result in conformational

changes in the membrane molecules Studies at both a cell level

and of whole lung have shown that overdistention can alter cell

metabolism leading to a cascade of cytokines and chemokines

which are proinfl ammatory and lead to further lung injury [21]

Thus, there is good evidence that overdistention of the lung

promotes lung injury However, at this point our ability to assure

Those who routinely use a fl ow - infl ating bag believe it gives greater responsiveness and greater individual control Self infl ating bags, however, require less expertise and experience to use effectively than do fl ow - infl ating bags They will require a special attachment to provide end - expiratory pressure (PEEP); however, they cannot deliver CPAP Self - infl ating bags also require an oxygen reservoir to provide variable concentrations of oxygen

To guard against the delivery of excessive pressure to the infant ’ s lungs, all resuscitation bags should be equipped with a pressure gauge, a pressure - relief valve (pop - off valve) or both Pop - off valves ideally vent pressures of greater than 30 – 40 cmH 2 O, but great variability can exist between individual bags [16] Should pressures greater than 30 – 40 cmH 2 O be needed to estab-lish adequate chest rise, a fi nger can easily be placed over the pop - off valve Any bag without a pop - off valve should have a pressure gauge Pressure gauges with built - in pressure release valves are available

A T - tube device capable of providing both CPAP and PEEP, controlling the peak - inspiratory pressure as well as the

inspira-tory time, has been developed (Figure 8 7 ) The most common

one on the market today is called the NeoPuff ®

It is important to check any apparatus for defects before every resuscitation Reusable bags will develop leaks and cracks over time, and bag reassembly after cleaning may not be correct It is greatly preferable to discover a faulty bag and mask before it is urgently needed The apparatus can quickly be checked for func-tion by occluding the air outlet and squeezing the bag or occlud-ing the openocclud-ing in the T - tube A pressure should be generated and refl ected on the pressure gauge and/or the pop - off valve should vent air above 30 – 40 cmH 2 O

Use of m ask - CPAP

As pointed out previously, in infants who are breathing yet exhibit some degree of respiratory distress and/or an oxygen need, the use of CPAP has become increasingly more common The easiest way to do this is with the NeoPuff® After setting the

F i O 2 and the desired degree of continuous positive airway pres-sure, the attached mask can be sealed to the face, permitting the infant to exhale against a continuous pressure The same effect can be obtained with a fl ow infl ating bag by use of the fl ow control valve

Although there are no well - established values at which to start CPAP most neonatologists will begin with at least 5 cmH 2 O pres-sure and move up, if necessary It is uncommon to go to prespres-sures

in excess of 8 cmH 2 O Care must be taken to avoid providing excessive end - expiratory pressure to an infant with good lung compliance

Use of p ositive - p ressure v entilation

In the infant who is not breathing, has inadequate respirations to keep the heart rate above 100 or who has an excessive work of breathing and a high F i O 2 requirement on CPAP, there is a need for positive - pressure ventilation Any of the three devices that

respiratory distress The goal is the same as discussed above,

namely helping to recruit and maintain alveoli open by

prevent-ing collapse of alveoli at end - expiration In breathprevent-ing preterm

lambs when the use of CPAP was compared with intubation and

positive - pressure ventilation, it has been shown that at 2 hours

of age, those animals resuscitated and treated only with CPAP

have higher lung volumes, as well as less evidence of an infl

am-matory response or acute lung injury [28]

In 1987 the incidence of chronic lung disease was examined at

eight institutions throughout the United States Of note was the

fact that Columbia University, had the lowest incidence of chronic

lung disease and the most frequent use of CPAP as method of

resuscitation and ventilatory support in the nursery [29] This

was confi rmed again in 2000 when the incidence of chronic lung

disease was examined at two Boston hospitals (22%) and

com-pared to the hospital at Columbia University (4%) The

conclu-sion of the paper was that “ … most of the increased risk of CLD

among very low birth weight infants hospitalized at 2 Boston

NICUs, compared with those at Babies ’ Hospital, was explained

simply by the initiation of mechanical ventilation ” [30]

There are a great number of cohort studies indicating that the

use of CPAP for ventilatory support in the delivery room reduces

the number of infants who need to be ventilated There are,

however, no randomized, controlled clinical trials of suffi cient

power that compare the use of CPAP with positive - pressure

ven-tilation in neonatal resuscitation In spite of the lack of “ gold

standard ” trials, the use of CPAP is becoming more and more

accepted [31] The 2006 edition of the American NRP points out

that “ Some neonatologists recommend administering CPAP to a

spontaneously breathing baby … ” The Australian Neonatal

Resuscitation guidelines point out that there are no randomized

controlled trials of CPAP and then go on to say: “ However, there

is accumulating evidence that it is benefi cial and no evidence of

harm when used with babies with stiff lungs Therefore, CPAP or

PEEP (at least 5 cmH 2 O) should now be considered when

resus-citating very premature infants ” [32]

Resuscitation d evices

It is now recommended that any device used in assisted

ventilation be capable of controlling peak inspiratory pressure and end

expiratory pressure as well as inspiratory time In addition, the

device should be able to deliver a variable amount of oxygen

ranging from room air to 100%

There are three devices currently in use that, with various

degrees of ease, can meet these requirements These are the self

infl ating bag, the fl ow - infl ating bag and a T - tube device with

CPAP and PEEP capability Regardless of what device is used,

those who participate as part of the neonatal resuscitation team

should be trained, comfortable and profi cient in its use

If a self - infl ating or fl ow - infl ating bag is used, the volume must

be appropriate for the newborn infant (200 – 750 mL total volume)

and capable of delivering high concentrations of oxygen An

infant will only require between 5 and 8 cc/kg with each

ventila-tion A large bag makes it diffi cult to provide such small volumes

Circult Pressure Inspiratery Pressure Control

Maximum Pressure Relief

Gas Outlet Gas Intlet

Figure 8.7 T - tube device capable of providing

CPAP and PEEP (Reproduced from Textbook of

Neonatal Resuscitation , 5th edn Elk Grove, IL:

American Academy of Pediatrics/American Heart

Association, 2006: 3 – 55.)

Table 8.1 Problems associated with inadequate chest expansion

Problem Correction

Inadequate face mask seal Reapply mask to face

Alter position of hand that holds mask

Bag and mask Check infant ’ s position

Suction mouth, oropharynx, and nose Insert oral airway if indicated (Pierre – Robin, macroglossia)

Bag and endotracheal tube Suction the tube Misplaced endotracheal tube Remove endotracheal tube, ventilate with

bag and mask, replace tube Inadequate pressure Increase pressure, taking care not to

overexpand the chest; may require adjusting or overriding the pop - off valve (Reproduced by permission from Faranoff AA, Martin, RJ, eds Neonatal - Perinatal Medicine: Diseases of the Fetus and Newborn , 7th edn St Louis: Mosby, 2002: 429.)

have been discussed are capable of providing positive - pressure

ventilation However, in order to add end - expiratory pressure to

prevent alveolar collapse at end - expiration, one needs to add a

device to the self - infl ating bag Initially, positive - pressure

ventila-tion will be provided with a mask

Positive - pressure ventilation, like the fi rst spontaneous breaths

in the healthy infant, must establish FRC and an adequate tidal

volume to halt the development or progression of the asphyxial

process To prevent overdistention of the lungs, the goal is to use

just enough pressure to effect an improvement in heart rate,

oxygen saturation/color, muscle tone and spontaneous breathing

The fi rst breaths may require a greater peak inspiratory pressure

and a longer inspiratory time than subsequent breaths It is

rec-ommended that the rate of ventilation should be between 40 and

60 breaths per minute

If the infant improves, yet continues to need positive - pressure

ventilation, be aware of how much tidal volume you are

provid-ing If the chest movement is enough to make the infant appear

to be taking deep breaths, you are probably overinfl ating the

lungs In addition, to increasing the risk of the type of lung

damage we previously discussed, you are also at an increased risk

for producing a pneumothorax

If no improvement occurs with the fi rst few breaths, it may be

necessary to increase the inspiratory pressure However, before

you do this, check to see if there is any chest movement and have

someone listen with a stethoscope to assess breath sounds If these

are poor fi rst check to see if there is an adequate seal between the

mask and the face and make sure the airway is not blocked If

these are OK, and there is no improvement, increase the pressure

If there continues to be no improvement, it may be necessary to

intubate the infant and provide positive pressure through the

endotracheal tube Table 8.1 describes common problems

associ-ated with inadequate chest expansion and potential corrective actions easily performed in the delivery room

Endotracheal i ntubation

The task of endotracheal intubation is best accomplished by two people One inserts the tube into the airway, while the other assists and then assesses for correct placement of the tube by listening for equal breath sounds on both sides of the chest Uncuffed endotracheal tube sizes ranging from 2.0 to 4.0 should

be available in the delivery suite A 2.5 endotracheal tube will be

the animal and human work can be gleaned from two recent review articles [33,34] Multiple animal studies have provided evidence indicating that the generation of oxygen free radicals during the reperfusion phase of ischemic injury is associated with increased damage After a pilot study demonstrating no difference in outcomes of resuscitation with room air versus 100% oxygen, a seminal and, to date, the only large multicenter controlled study was done [35] This study enrolled 609 infants

to more rigorously test the hypothesis that room air resuscitation

of the asphyxiated infant would not increase morbidity and mortality There were no signifi cant differences in mortality, incidence and severity of hypoxic - ischemic encephalopathy, acid – base status, oxygen saturations or arterial oxygen concentrations

There are human data to indicate that the initial use of 100% oxygen increases the time to the onset of spontaneous respiration, increases the time of resuscitation, results in a lower 5 - minute Apgar score, increases oxidative stress and results in some, at least

in the short term, oxidative injury in the kidney and heart There

is also a suggestion that there is an increased neonatal mortality, although this fi nding is debated There have been a limited number of randomized controlled human studies, which indi-vidually and when looked at in a meta - analysis [36] indicated that starting resuscitation with room air and adding oxygen if needed, does no harm

The American NRP recommends that 100% oxygen should be used when resuscitating term infants with cyanosis or a need for positive pressure ventilation When resuscitating the pre - term infant one should use a blender and pulse oximeter and begin somewhere between room air and 100% oxygen; increasing or decreasing the F i O 2 upon the response of the infant

On the other hand, the Australian Neonatal Resuscitation Guidelines state that “ However, at present, the best available evidence suggests air should be used initially with supplemental oxygen reserved for infants whose condition does not improve after effective ventilatory support ” [32] The Canadian recom-mendations indicate that positive - pressure ventilations should be initiated with room air and supplemental oxygen used at 90 seconds of age if the heart rate is below 100 beats per minute or cyanosis persists [37] Others have suggested starting with an F i O 2

of 40% and moving up or down as necessary

Chest c ompressions

As emphasized above, in all but a fraction of 1% of infants, provi-sion of positive - pressure ventilation will be suffi cient to over-come any bradycardia and lead to spontaneous respirations If, however, after ventilation with 100% oxygen, the newborn remains bradycardic, chest compressions will be needed to main-tain systemic blood fl ow

The American Heart Association/American Academy of Pediatrics currently recommends beginning chest compression for a heart rate of less than 60 beats/min This can be done with the two - fi nger method, or the thumb method may be used to

small enough for all but the 500 – 600 - g, extremely low birth

weight infants (Table 8.2 ) If a soft, fl exible wire stylet is used to

assist with endotracheal tube placement, it should not extend past

the tip of the endotracheal tube, thus ensuring that the stylet does

not damage the tracheal wall or carina A tip to lip distance in cm

should be used to estimate depth of placement (Table 8.3 )

When the tube is placed in the airway, whichever resuscitation

device one is using should be attached to the endotracheal tube

and a series of breaths initiated Placement should initially be

checked both by auscultation of equal breath sounds on both

sides of the chest along with a lack of signifi cant auscultated

gastric breath sounds or of signifi cant gastric distension The

placement should be confi rmed by the use of a small, portable

exhaled CO 2 detector

Complications of endotracheal intubation include hypoxia,

bradycardia, infection and contusions or lacerations to the

struc-tures of the upper airway, including the vocal cords themselves

Rarely but tragically, the trachea or esophagus will be perforated

The utmost care must be given to placement of the endotracheal

tube to avoid such complications Even more vigilance must be

exercised if an endotracheal tube is placed with the use of a stylet

Room a ir v ersus 100% o xygen

The use of room air as opposed to 100% oxygen in the

resuscita-tion of an infant is a source of much debate The references for

Table 8.2 Endotracheal tube sizes

Tube size (mm ID) Weight (g) Gestational age (weeks)

2.0 * 500 – 600 or less 25 – 26 or less

3.5 – 4.0 > 3000 > 38

* May be needed if a size 2.5Fr tube does not fi t

ID, internal diameter

(Reproduced by permission from Faranoff AA, Martin, RJ, eds Neonatal - Perinatal

Medicine: Diseases of the Fetus and Newborn , 7th edn St Louis: Mosby, 2002:

426.)

Table 8.3 Endotracheal tube placement

Weight (kg) Depth of insertion (cm from upper lip)

* Infants weighing less than 750 g may require only 6 cm insertion

(Reproduced by permission from Textbook of Neonatal Resuscitation , 4th edn

Elk Grove, IL: American Academy of Pediatrics/American Heart Association,

2000: 5 – 19.)