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Respiratory Support in Neonates and Infants

by James W. Kendig, MD, Ursula Nawab, MD

Initial stabilization maneuvers include mild tactile stimulation, head positioning, and suctioning of the mouth and nose followed as needed by

  • Supplemental O 2

  • Continuous positive airway pressure (CPAP)

  • Noninvasive positive pressure ventilation (NIPPV)

  • Bag-and-mask ventilation or mechanical ventilation

Neonates who cannot be oxygenated by any of these means may require a full cardiac evaluation to exclude congenital heart disease and treatment with high-frequency oscillatory ventilation, nitric oxide, extracorporeal membrane oxygenation, or a combination.

Oxygen

O 2 may be given using a nasal cannula, face mask, or O 2 hood, with O 2 concentration set to achieve a Pa o 2 of 50 to 70 mm Hg in preterm infants and 50 to 80 mm Hg in term infants or an O 2 saturation of 90 to 94% in preterm infants and 92 to 96% in term infants. Lower Pa o 2 in preterm infants provides almost full saturation of Hb, because fetal Hb has a higher affinity for O 2 ; maintaining higher Pa o 2 increases the risk of retinopathy of prematurity (see Retinopathy of Prematurity). No matter how O 2 is delivered, it should be warmed (36 to 37° C) and humidified to prevent secretions from cooling and drying and to prevent bronchospasm.

An umbilical artery catheter (UAC) is usually placed for sampling ABGs in neonates who require fraction of inspired O 2 (F io 2 ) 40%. If a UAC cannot be placed, a percutaneous radial artery catheter can be used for continuous BP monitoring and blood sampling.

Neonates who are unresponsive to these maneuvers may require fluids to improve cardiac output and are candidates for CPAP ventilation or bag-and-mask ventilation (40 to 60 breaths/min). If the infant does not oxygenate with or requires prolonged bag-and-mask ventilation, endotracheal intubation with mechanical ventilation is indicated, although very immature neonates (eg, < 28 wk gestation or < 1000 g) are typically begun on ventilatory support immediately after delivery so that they can receive preventive surfactant therapy. Because bacterial sepsis is a common cause of respiratory distress in neonates, it is common practice to draw blood cultures and give antibiotics to neonates with high O 2 requirements pending culture results.

Continuous positive airway pressure (CPAP)

CPAP delivers O 2 at a positive pressure, usually 5 to 7 cm H 2 O, which keeps alveoli open and improves oxygenation by reducing the amount of blood shunted through atelectatic areas while the infant breathes spontaneously. CPAP can be provided using nasal prongs and various apparatuses to provide the positive pressure; it also can be given using an endotracheal tube connected to a conventional ventilator with the rate set to zero. CPAP is indicated when F io 2 40% is required to maintain acceptable Pa o 2 (50 to 70 mm Hg) in infants with respiratory disorders that are of limited duration (eg, diffuse atelectasis, mild respiratory distress syndrome, lung edema). In these infants, CPAP may preempt the need for positive pressure ventilation.

Noninvasive positive pressure ventilation (NIPPV)

NIPPV (see also Noninvasive positive pressure ventilation (NIPPV)) delivers positive pressure ventilation using nasal prongs or nasal masks. It can be synchronized (ie, triggered by the infant's inspiratory effort) or nonsynchronized. NIPPV can provide a back-up rate and can augment an infant's spontaneous breaths. Peak pressure can be set to desired limits. It is particularly useful in patients with apnea to facilitate extubation and to help prevent atelectasis.

Mechanical ventilation

Endotracheal tubes are required for mechanical ventilation (see also Endotracheal tubes):

  • Endotracheal tubes 2.5 mm in diameter (the smallest) typically used for infants < 1250 g

  • 3 mm for infants 1250 to 2500 g

  • 3.5 mm for infants > 2500 g

Intubation is safer if O 2 is insufflated into the infant’s airway during the procedure. Orotracheal intubation is preferred. The tube should be inserted such that the

  • 7-cm mark is at the lip for infants who weigh 1 kg

  • 8-cm mark for 2 kg

  • 9-cm mark for 3 kg

The endotracheal tube is properly placed when its tip can be palpated through the anterior tracheal wall at the suprasternal notch. It should be positioned about halfway between the clavicles and the carina on chest x-ray, coinciding roughly with vertebral level T2. If position or patency is in doubt, the tube should be removed and the infant should be supported by bag-and-mask ventilation until a new tube is inserted. Acute deterioration of the infant’s condition (sudden changes in oxygenation, ABGs, BP, or perfusion) should trigger suspicion of changes in the position of the tube, patency of the tube, or both.

Ventilators can be set to deliver fixed pressures or volumes; can provide assist control (AC, in which the ventilator is triggered to deliver a full breath with each patient inspiration) or intermittent mandatory ventilation (IMV, in which the ventilator delivers a set number of breaths within a time period, and patients can take spontaneous breaths in between without triggering the ventilator); and can be normal or high frequency (delivering 400 to 900 breaths/min). Optimal mode or type of ventilation depends on the infant’s response. Volume ventilators are considered useful for larger infants with varying pulmonary compliance or resistance (eg, in bronchopulmonary dysplasia), because delivering a set volume of gas with each breath ensures adequate ventilation. AC mode is often used for treating less severe pulmonary disease and for decreasing ventilator dependence while providing a small increase in airway pressure or a small volume of gas with each spontaneous breath. High-frequency jet, oscillatory, and flow-interrupter ventilators are used in extremely premature infants (< 28 wk) and in some infants with air leaks, widespread atelectasis, or pulmonary edema (see Pulmonary Edema).

Initial ventilator settings are estimated by judging the severity of respiratory impairment. Typical settings for an infant in moderate respiratory distress are F io 2 = 40%; inspiratory time (IT) = 0.4 sec; expiratory time =1.1 sec; IMV or AC rate = 40 breaths/min; peak inspiratory pressure (PIP) = 15 cm H 2 O for very low-birth-weight infants and up to 25 cm H 2 O for near-term infants; and positive end-expiratory pressure (PEEP) = 5 cm H 2 O. These settings are adjusted based on the infant’s oxygenation, chest wall movement, breath sounds, and respiratory efforts along with arterial or capillary blood gases.

  • Pa co 2 is lowered by increasing the minute ventilation through an increase in tidal volume (increasing PIP or decreasing PEEP) or an increase in rate.

  • Pa o 2 is increased by increasing the F io 2 or increasing the mean airway pressure (increasing PIP, PEEP, or rate or prolonging IT).

Patient-triggered ventilation often is used to synchronize the positive pressure ventilator breaths with the onset of the patient’s own spontaneous respirations. This seems to shorten the time on a ventilator and may reduce barotrauma. A pressure-sensitive air-filled balloon attached to a pressure transducer (Graseby capsule) taped to the infant’s abdomen just below the xiphoid process can detect the onset of diaphragmatic contraction, or a flow or temperature sensor placed at the endotracheal tube adapter can detect the onset of a spontaneous inhalation.

Ventilator pressures or volumes should be as low as possible to prevent barotrauma and bronchopulmonary dysplasia; an elevated Pa co 2 is acceptable as long as pH remains 7.25 (permissive hypercapnia). Likewise, a Pa o 2 as low as 40 mm Hg is acceptable if BP is normal and metabolic acidosis is not present.

Adjunctive treatments used with mechanical ventilation in some patients include

  • Paralytics

  • Sedation

  • Nitric oxide

Paralytics (eg, vecuronium or pancuronium bromide 0.03 to 0.1 mg/kg IV q 1 to 2 h prn [with pancuronium, a test dose of 0.02 mg/kg is recommended in neonates]) and sedatives (eg, fentanyl 1 to 4 mcg/kg IV push q 2 to 4 h or midazolam 0.05 to 0.15 mg/kg IV over 5 min q 2 to 4 h) may facilitate endotracheal intubation and can help stabilize infants whose movements and spontaneous breathing prevent optimal ventilation. These drugs should be used selectively, however, because paralyzed infants may need greater ventilator support, which can increase barotrauma. Inhaled nitric oxide 5 to 20 ppm may be used for refractory hypoxemia when pulmonary vasoconstriction is a contributor to hypoxia (eg, in idiopathic pulmonary hypertension, pneumonia [see Neonatal Pneumonia], or congenital diaphragmatic hernia [see Diaphragmatic Hernia]) and may prevent the need for extracorporeal membrane oxygenation (see Extracorporeal membrane oxygenation (ECMO)).

Weaning from the ventilator can occur as respiratory status improves. The infant can be weaned by lowering

  • F io 2

  • Inspiratory pressure

  • Rate

Continuous-flow positive pressure ventilators permit the infant to breathe spontaneously against PEEP while the ventilator rate is progressively slowed. As the rate is reduced, the infant takes on more of the work of breathing. Infants who can maintain adequate oxygenation and ventilation on lower settings typically tolerate extubation. The final steps in ventilator weaning involve extubation, possibly support with nasal (or nasopharyngeal) CPAP or NIPPV, and, finally, use of a hood or nasal cannula to provide humidified O 2 or air.

Very low-birth-weight infants may benefit from the addition of a methylxanthine (eg, aminophylline, theophylline, caffeine) during the weaning process. Methylxanthines are CNS-mediated respiratory stimulants that increase ventilatory effort and may reduce apneic and bradycardic episodes that may interfere with successful weaning. Caffeine is the preferred agent because it is better tolerated, easier to give, safer, and requires less monitoring. Corticosteroids, once used routinely for weaning and treatment of chronic lung disease, are no longer recommended in premature infants because risks (eg, impaired growth and neurodevelopmental delay) outweigh benefits. A possible exception is as a last resort in near-terminal illness, in which case parents should be fully informed of risks.

Complications

Mechanical ventilation complications more common among neonates include

  • Pneumothorax

  • Asphyxia from endotracheal tube obstruction

  • Ulceration, erosion, or narrowing of airway structures due to adjacent pressure

  • Bronchopulmonary dysplasia

Extracorporeal membrane oxygenation (ECMO)

ECMO is a form of cardiopulmonary bypass used for infants who cannot be oxygenated adequately or ventilated with conventional ventilators. Eligibility criteria vary by center, but in general, infants should have reversible disease (eg, persistent pulmonary hypertension of the newborn [see Persistent Pulmonary Hypertension of the Newborn], congenital diaphragmatic hernia, overwhelming pneumonia) and should have been on mechanical ventilation < 7 days.

After systemic heparinization, blood is circulated through large-diameter catheters from the internal jugular vein into a membrane oxygenator, which serves as an artificial lung to remove CO 2 and add O 2 . Oxygenated blood is then circulated back to the internal jugular vein (venovenous ECMO) or to the carotid artery (venoarterial ECMO). Venoarterial ECMO is used when both circulatory support and ventilatory support are needed (eg, in overwhelming sepsis). Flow rates can be adjusted to obtain desired O 2 saturation and BP.

ECMO is contraindicated in infants < 34 wk, < 2 kg, or both because of the risk of intraventricular hemorrhage with systemic heparinization. Complications include thromboembolism, air embolization, neurologic (eg, stroke, seizures) and hematologic (eg, hemolysis, neutropenia, thrombocytopenia) problems, and cholestatic jaundice.

Drugs Mentioned In This Article

  • Drug Name
    Select Trade
  • No US brand name
  • ACTIQ, DURAGESIC, SUBLIMAZE
  • ELIXOPHYLLIN

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