NEONATAL TRANSITION

Although neonatologists use the term resuscitation we rarely practise resuscitation as the adult doctors understand it. An adult who collapses lifeless needs very urgent chest compressions, cardioversion and ventilation. Such an episode is very uncommon in neonates. Wyckoff et al suggests that it probably occurs in less than 1:2000 deliveries.1 Newborn infants who do not breathe sufficiently need gentle assistance to make the transition from placental to pulmonary gas exchange.

LUNG AERATION AND OXYGENATION

Apnoea and bradycardia after birth are caused by relative hypoxia of the brain stem and myocardium. At birth the lungs are not aerated and filled with lung liquid. If infants do not breathe adequately they need assistance aerating their lungs and forming a functional residual capacity (FRC). Oxygenation of the myocardium then improves and the heart rate and blood pressure rapidly increase. Shortly thereafter the brain stem recovers and breathing starts. Most apnoeic newborn infants respond well to effective aeration of the lungs. If the heart rate does not increase quickly then the ventilation technique is probably unsatisfactory. Cardiac massage is rarely needed if the ventilation is adequate.

100% OXYGEN OR AIR

Treating newborn infants at birth with 100% oxygen is traditional.2^–5 However, 100% oxygen may cause injury and should be used cautiously.6 7 Free radical damage to the newborn and in particular the preterm infant is well recognised.8 9 A meta-analysis of randomised controlled trials suggests that using 100% oxygen is associated with an increased mortality compared with air.10

PULSE OXIMETRY

Observing whether a newborn infant is cyanosed is part of the traditional assessment. However, it is subjective and cannot be reliably used to decide on the appropriate fraction of inspired oxygen (FiO₂).11 Recent studies show that it is possible to obtain accurate oximetry readings of heart rate and oxygen saturation, from the right hand or wrist, within 90 s of birth.12

During both stabilisation and full resuscitation, after birth the heart rate is the key sign of an infant’s response. A continuous display of heart rate is very useful. The present technique of intermittently listening to the heart rate, counting for 6 s and multiplying by 10 is inaccurate.13 The sicker the infant, the more important the heart rate and the less the resuscitative efforts should be interrupted. Pulse oximetry displays heart rate continuously, making it useful during difficult resuscitations.

Pulse oximetry continuously displays oxygen saturation (SpO₂). However, resuscitators need to be taught what is normal in the first minutes of life. In utero, the SpO₂ is about 60% and during labour and delivery it can fall to 30%.14 Immediately after birth normal term infants have an SpO₂ about 60% which rises over the next 10 min to over 90%. At 5 min the lower end of the normal range is ∼70%.15 16 When considering whether to use oxygen it is important to appreciate that having a relatively low SpO₂ in the first few minutes is not, on its own, an indication for oxygen therapy. Aiming for SpO₂ values similar to those used in the neonatal intensive care unit will lead to inappropriate oxygen treatment after birth.

Others suggest that infants be resuscitated with an intermediate level of inspired oxygen. Whatever the starting concentration chosen, oxygen delivery can now be titrated against the infant’s SpO₂ bearing in mind the normal changes seen in the first minutes of life.15

CONTINUOUS POSITIVE AIRWAY PRESSURE AND POSITIVE END EXPIRATORY PRESSURE

Immediately after birth the lungs must aerate and develop an FRC. Oxygenation is related to lung volume. If the infant does not breathe deeply, the lungs will not aerate adequately and form an FRC. These infants will need respiratory support. Studies in newborn animals have shown that positive end expiratory pressure (PEEP) improves oxygenation within minutes of birth by increasing the FRC.17 18 The use of PEEP reduces lung injury and improves the lung volume by 2 h after birth.19

A randomised controlled trial of two techniques of ventilating preterm infants after birth compared a self-inflating bag with a 10 s prolonged inflation followed immediately by continuous positive airway pressure (CPAP)/PEEP and showed more infants were subsequently intubated and ventilated in the group without CPAP/PEEP.20

To facilitate lung aeration, a device is needed that delivers PEEP during ventilation and CPAP to spontaneously breathing infants. Self-inflating bags cannot produce PEEP and are not ideal for resuscitating sick infants. Addition of a PEEP valve partially corrects the problem but does not allow provision of CPAP. A flow inflating bag can be used to give PEEP but the level is very variable.21 A T piece device can accurately provide both PEEP and CPAP and is therefore probably the most appropriate for respiratory support of very preterm infants. CPAP can be given immediately after birth through a facemask or nasal prong.

USE OF A CARBON DIOXIDE DETECTING DEVICE AFTER INTUBATION

Intubating newborn infants is difficult.22 23 It may be hard to determine whether the endotracheal tube is in the trachea and the clinician may take minutes to realise that the poor response to ventilation is because the endotracheal tube is misplaced.24 A colorimetric carbon dioxide detector attached to the endotracheal tube gives a rapid detection of carbon dioxide in expired air within six inflations.25 When carbon dioxide is detected, the colour changes from purple to yellow.

If there is no colour change after a few inflations the likely causes are: the endotracheal tube is not in the trachea; the inflating pressure is inadequate; or no carbon dioxide is being produced because of absent lung perfusion due to cardiac arrest.

We recommend an exhaled carbon dioxide detector is used for verification of correct tube placement every time an infant is intubated.

LUNG INJURY DURING RESUSCITATION

Bjorklund et al26 showed that just six large volume inflations severely injured the lungs of newborn lambs. The lungs of newborn infants probably can be damaged in the first few minutes by large tidal volumes. The tidal volume delivered is determined by the peak inflating pressure and total chest compliance. Tidal volume is not measured while ventilating immediately after birth. The pressure used varies between about 20 cm H₂O and 40 cm H₂O depending on resuscitation guidelines. The problem with a fixed inflating pressure is that the tidal volume will vary widely depending on: the compliance of the lungs, the infant’s spontaneous breathing efforts and the leak at the face mask or endotracheal tube. These can change during a resuscitation. Without measuring tidal volume it is possible the tidal volume will be damagingly high or too low causing inadequate ventilation. The lungs can be damaged by repeated inflation from a collapsed state. This is called atelectrauma, and occurs if very premature infants are ventilated without PEEP.

If very preterm infants are over-ventilated and become hypocarbic they are at increased risk of adverse neurodevelopmental outcomes.27 Tracy et al28 showed about 20% of very preterm infants become dangerously hypocarbic (Paco₂ <20 mm Hg, ∼3 kPa) within minutes of ventilation after birth. To avoid injuring the lungs and inducing hypocarbia we should consider measuring and controlling tidal volumes during ventilation in the delivery room.

FACEMASK LEAKS

Successful neonatal facemask ventilation requires an airtight seal between the mask and face.29^–31 Achieving this can be difficult.32 Leak at the mask is a common reason for failure of ventilation.29 Efficacy of mask ventilation is judged by observing chest rise and an increase in heart rate.33 Even when the set pressure is achieved large leaks can occur in the presence of a high gas flow into the system.34^–36 With variable leaks there will be variable tidal volumes. Improved techniques of holding face masks can be taught.37 38

INTUBATION OR CPAP FOR VERY PRETERM INFANTS?

Despite antenatal corticosteroids,39 surfactant40 and improved ventilation techniques, the incidence of bronchopulmonary dysplasia (BPD) has not decreased.41 42 Observational studies have suggested treating very preterm infants with early CPAP may reduce the intubation rate and incidence of BPD without increasing morbidity.43^–55 Some have suggested CPAP may be started at birth for most infants above 25 weeks’ gestation.56 Vanpee et al57 recently compared two nurseries and found that one unit, with a policy of intubating all infants delivered <28 weeks gestation, had a higher rate of oxygen treatment at term than a unit which used early CPAP.

The COIN trial58 randomly allocated infants born at 25–28 weeks’ gestation, who breathed at birth, to nasal CPAP or intubation and ventilation. There was no difference in mortality. At 28 days the CPAP group had a markedly lower incidence of death or oxygen treatment (54% vs 65%). By 36 weeks’ gestation there was no remarkable difference in death or oxygen treatment (34% vs 39%). There were no significant differences in any complications of prematurity except there was a marked increase in pneumothorax in the CPAP group (9% vs 3%). The CPAP group had significantly fewer days’ ventilation. This trial confirms that not all preterm infants need to be intubated at birth and many can be managed with CPAP at birth. If CPAP treatment fails to adequately support their breathing and they are intubated their outcome will be no worse than infants who are routinely intubated.

SURFACTANT

For two decades surfactant has been standard treatment for very preterm infants.59 60 Randomised trials showed it reduced mortality and pneumothoraces. However, these trials were in an era when most very preterm infants were electively intubated, rarely received early CPAP, and few had antenatal steroid treatment. It is therefore possible that these data do not apply to the present era.

There are suggestions that infants treated with early CPAP, who have a high FiO₂ requirement, have a lower incidence of ventilation and fewer pneumothoraces if they are transiently intubated and treated with surfactant.61 However, there is also evidence that very preterm infants managed with early CPAP do not need surfactant.43 Ammari et al55 reported their hospital’s experience of early nasal CPAP. They found that 76% of infants weighing <1251 g and 50% of those <751 g were not treated with surfactant. This suggests it is possible to start CPAP treatment in very preterm infants and only treat them with intubation and surfactant if they require ventilation for respiratory failure.

CONCLUSION

Current research is challenging widely held views about neonatal “resuscitation” and that a less aggressive, more gentle, approach may actually be more beneficial. It seems that 100% oxygen is inappropriate as the initial gas. Pulse oximetry is useful for monitoring difficult resuscitations. CPAP and PEEP support lung aeration and oxygenation. Carbon dioxide detectors can confirm endotracheal intubation. The technique of holding facemasks needs to be improved. Not all very preterm infants need to be intubated and treated with surfactant. Even very preterm infants may be successfully supported from birth with CPAP. There is still a great deal to learn about how to improve the care of infants during the transition to breathing.