Other Causes of Respiratory Failure

There are other causes of respiratory failure. These causes must be ruled out if the response to resuscitation is not immediate.

Pneumothorax

Pneumothorax occurs in 1% of all vaginal deliveries, in 10% of meconium-stained neonates,^[72] and in 2% to 3% of neonates who require mechanical ventilation in the delivery room. To detect a pneumothorax, the chest should be carefully examined. The hemithorax containing free air is usually hyperexpanded (because of the very compliant chest wall) and moves poorly with ventilation. The point of maximum cardiac impulse is shifted toward the chest that does not have a pneumothorax. The heart tones may be muffled.

If a pneumothorax is suspected, a small, high-intensity, cold light should be placed directly on the skin of the neonate's chest and shone onto the skin.^[81] If a pneumothorax exists, the involved chest will glow. A 22-gauge, relatively blunt needle should be inserted into the second intercostal space in the midclavicular line. The needle should be occluded with a closed stopcock. A "pop" can be felt when the needle enters the pleural cavity. Fixing the needle at skin level with a hemostat reduces the likelihood of the needle advancing too far into the chest and accidentally damaging the lung. If gas is found in the pleural space, as much of the gas as possible should be removed with a syringe while a thoracostomy tube is being inserted. The thoracostomy tube should be connected to underwater drainage.

Congenital Anomalies

Congenital anomalies of the airway are relatively common. Choanal atresia is discussed in the section on initial evaluation. Micrognathia (i.e., Pierre Robin syndrome) and relative macroglossia cause inspiratory obstruction. If an oral airway can be inserted, the problem is usually temporarily solved. If an oral airway cannot be inserted, a large (10F) orogastric tube should be inserted through the mouth and the tip of the catheter placed in the stomach. This maneuver prevents the tongue from making a tight seal with the pharyngeal wall, which prevents the neonate from developing large negative pressures in the pharynx and "sucking" the tongue into the pharynx. The neonate may make significant inspiratory noise with breathing, but there should be adequate gas entry. Grasping the tongue with a towel clip and pulling outward is seldom effective and may cause harm. However, in a life-threatening situation, this maneuver should be tried. The tips of the towel clip should be placed side to side on the tongue, not top to bottom. Neonates with micrognathia should be nursed in the prone position to let the tongue fall forward. It is seldom necessary to do a tracheotomy; however, it is occasionally necessary to intubate the trachea. It is also possible to insert a no. 1 laryngeal mask; this often provides a good airway.^[82] However, the connecting tube is a large dead space and may significantly increase the PaCO₂ .

Congenital anomalies of the larynx, such as webs, atresia, and vocal cord paralysis or fusion, are uncommon, but when present, they cause stridor and respiratory distress. Occasionally, it may be necessary to force a small endotracheal tube through these lesions. Subglottic stenosis, subglottic webs, and subglottic hemangiomas are also uncommon, but, if present, they cause severe airway obstruction.

Esophageal Atresia and Tracheoesophageal Fistulas

Esophageal atresia and tracheoesophageal fistulas occur in 1 of 2400 to 4500 births. Respiratory distress occurs if the neonate aspirates gastric secretions or esophageal pouch secretions or if the stomach and gut distend with air and limit movement of the diaphragm. Controlled ventilation may distend the gut further and should be avoided unless it is absolutely necessary. If it is necessary to ventilate the lungs, the tip of the endotracheal tube should first be advanced beyond the fistula. Breath sounds heard over the stomach diminish in intensity at this time. After ensuring that both lungs are being ventilated equally (i.e., equal chest movement and breath sounds), the endotracheal tube is firmly fixed in place. A sump-type catheter should be placed into the esophageal pouch and the catheter connected to suction to prevent accumulation of secretions in the pouch. The neonate should be nursed in the reverse Trendelenburg position to reduce the likelihood of aspirating the contents of the stomach and pouch.

Diaphragmatic Hernia

Diaphragmatic hernia occurs in 1 of 2000 births. If the hernia is large, gut fills the involved chest cavity (usually the left) and causes hypoplasia of both lungs.^[83] The ipsilateral lung is about 10% to 20% of its normal size,

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The trachea should be intubated and the lungs ventilated rapidly (60 to 150 times per minute) with small breaths. No attempt should be made to expand the hypoplastic lung, because this may cause a pneumothorax on the side of the "good" lung. Neonates with diaphragmatic hernias are usually hypovolemic and require expansion of their intravascular volume with whole blood or plasma. Overhydration should be avoided because it causes pulmonary edema and makes the PaO₂ and PaCO₂ worse. Correction of the acidosis (respiratory and metabolic) reduces PVR and improves pulmonary blood flow; reduced pulmonary blood flow is the usual cause of death. Hyperventilation (PaCO₂ of 20 to 25 mm Hg) often increases pulmonary blood flow and improves blood gases, ^[85] but it may reduce cerebral blood flow, especially if the baby is hypotensive. Hyperventilation should not be continued for protracted periods. It may be lifesaving, but it produces other serious problems.

ECMO has been used to treat pulmonary hypertension associated with diaphragmatic hernia.^[86] The success of this therapy has resulted in the survival of many neonates who otherwise would have died. Nevertheless, the mortality of neonates with a diaphragmatic hernia is still nearly 50%. Some of these infants die later of severe pulmonary hypertension.