NEONATAL RESUSCITATION AIRWAY BREATHING

Airway management
Once the infant is placed in a heated environment, the infant should be positioned to open the airway, and the mouth and nose should be suctioned. A bulb syringe should be used for the initial suctioning. Infants have a vagal reflex response to sensory stimulation of the larynx, which may induce hypotension, bradycardia, swallowing, and apnea. Therefore, the act of suctioning the airway with a catheter because of extremely thick or meconium-stained fluids may cause profound central apnea, bradycardia, and laryngospasm. This reflex bradycardia may be profound. Therefore, deep suctioning of the trachea should be limited to infants who have thick mucous that cannot be removed by bulb syringe or used for the aspiration of aspirate stomach contents, when necessary.

The instillation of saline into the trachea also has been shown to stimulate the afferent sensory neurons leading to these sequelae and has no place in the immediate resuscitation period. Lung inflation has been shown to reverse the effects of vagal stimulation. Vigorous suctioning of the nares with a catheter can lead to edema with resulting respiratory distress after the infant leaves the delivery room. Wall suction should be set so that pressures do not exceed 100 mm Hg.

Stimulation
Drying and suctioning often is enough stimulation to initiate breathing; however, if more vigorous stimulation is necessary, slapping the soles of the feet or rubbing the back may be effective. The back should be visualized briefly for any obvious defect in the spine before beginning these maneuvers. If there is no response to stimulation, it may be assumed the infant is in secondary apnea, and positive pressure ventilation should be initiated. At this point, the infant's respiratory rate, heart rate, and color should be evaluated. Most infants do not require further intervention.

Supplemental oxygen
Infants who have a sustained heart rate more than 100 beats per minute (BPM) and adequate respiratory effort but who remain cyanotic should receive blow-by oxygen via oxygen tubing or a mask. It is arguably advantageous to provide heated, humidified oxygen if possible, but this is rarely available in the delivery room environment. Supplemental oxygen should be initially provided with a FiO2 of 1 at a flow rate of 8-10 L/min. If supplemental oxygen is to be provided for a prolonged period, then heated humidified oxygen should be supplied via an oxy-hood with the FiO2 adjusted to result in pulse-oximetry saturations of 92-96% in the term infant and 88-92% in the preterm infant.

Positive pressure ventilation
For a number of reasons (discussed above), it can be difficult for the infant to clear fluid from the airways and establish air-filled lungs. Initial respiratory efforts may need to be augmented by the addition of either continuous positive airway pressure (CPAP) or positive pressure ventilation. The addition of positive pressure aids in the development of functional residual capacity and is needed more commonly in premature infants. Mechanical lung inflation also is important to reverse persistent bradycardia in an apneic asphyxiated infant.

Infants with adequate respirations who are having respiratory distress manifested by tachypnea, grunting, flaring, retracting, or persistent central cyanosis may benefit from CPAP. If the infant is apneic, has inadequate respiratory efforts, or a heart rate less than 100 BPM, then positive pressure ventilation should be initiated immediately. The bag must be equipped to deliver positive end-expiratory pressure and the appropriately sized mask should be applied firmly to the face.

Some infants respond to brief mechanical ventilation and subsequently begin independent ventilation; others need continued ventilatory support. It is essential that sufficient, but not excessive, initial pressure be used to adequately inflate the lungs, or bradycardia and apnea will persist. A pressure manometer always should be used with a pressure release valve limiting the positive pressure to 30-35 cm H2O. To provide adequate distending pressure, the infant must be positioned properly and the upper airway cleared of secretions; the mask must be the correct size and form a tight seal on the face.

While providing assisted breaths, look for a rise and fall in the chest and an immediate increase in heart rate. If no chest rise occurs, either the airway is blocked or insufficient pressure is being generated by the squeezing of the bag. Ventilatory rates of 40-60 breaths per minute should be provided initially, with proportionally fewer assisted breaths provided if the infant's spontaneous respiratory efforts increase. Although not studied extensively, it has been reported that the initial inflation of the newborn's lungs with either slow-rise or square wave inflation to 30 cm H2O pressure for approximately 5 seconds results in more rapid formation of a functional residual capacity.

It should be remembered that, at the moment of delivery and first, breath the neonatal lung is converting from a fetal, nonaerated status to a neonatal status. The neonatal lung has a requirement for gas exchange, and this requires the development of a functional residual capacity because of the resorption of lung fluid and the resolution of most of the atelectasis. Therefore, it is logical to conclude that initial slow ventilation with more prolonged inspiratory times may be useful to assist in this task, balanced with the avoidance of inappropriate inspiratory pressures.

However, these observations are counterbalanced with data showing that an increased risk of chronic lung disease in infants with very low birth weight is associated with centers who initiate mechanical ventilation more frequently. Therefore, prospective, randomized clinical trials are urgently needed to resolve several issues related to the timing of surfactant administration, use of various forms of positive end-pressure (CPAP), and/or initiation of mechanical ventilation.