Chapter 11:	The Infant
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Congenital Anomalies

Neonates experience a variety of respiratory and cardiac anomalies. The anomalies that can inflict the fetal respiratory tract during development include:

• an atresia of the upper esophagus with an accompanying fistula between the lower esophagus and trachea

• esophageal atresia without any fistula

• a normal esophagus and tracheas with a fistula connecting the two ("H" type)

• lower esophageal atresia with the upper esophagus attaching to the trachea

• both upper and lower esophageal attachments to the trachea

• choanal atresia (tissue blockage at the posterior nasal chamber)

• herniation of the diaphragm

• Pierre-Robin (micrognathia) which causes respiratory distress because of airway occlusion by the tongue

Cardiac defects occur in about 1 percent of all newborn deliveries, and the anomalies include:

• The ductus arteriosus sometimes fails to close following delivery (PDA), causing the shunting of blood away from the lungs and making it difficult for the newborn to maintain oxygenation.

• Defects in the atrial septum also cause blood to shunt from the left atrium to the right.

• Ventricular septal defects allow blood to shunt from the left ventricle to the right.

• The Tetralogy of Fallot is a well known defect that includes ventricular septal defects, an overriding aorta, hypertrophy of the right ventricle, and pulmonary valve obstruction.

• Transposition of the great vessel occurs when the aorta arises from the right ventricle, and the pulmonary artery arises from the left ventricle.

• Coarction of the aorta involves a constriction of the aorta, severely impeding the flow of blood.

• With tricuspid artesia, blood flow between the right atrium and ventricle is interrupted and shunting through the foramen ovale occurs.

• Anomalous venous return involves the return of pulmonary blood flow to the right atrium instead of the left.

• In truncus arteriosus, one large vessel acts both as the aorta and pulmonary artery.

• Hypoplastic left-heart syndrome involves outflow from the left ventricle being impeded by coarctation of the aorta and stenosis of the aortic valve.

The respiratory care provided neonates with these anomalies depends on whether the defects increase or decrease the flow of blood to the lungs. Defects that reduce pulmonary flow include tricuspid atresia and the Tetralogy of Fallot; increased blood flow is caused by VSD, coarctation of the aorta, subaortic stenosis, PDA, and anomalous venous return.

Lung compliance is generally increased in neonates with decreased pulmonary blood flow. Using high ventilatory pressures can further compromise blood flow and worsen V/Q ratios. By changing the frequency of ventilation instead of inspiratory pressures can help maintain low mean airway pressure while still meeting the neonate's ventilatory needs. Judicial use of oxygen is frequently required since high PaO₂ levels will increase the chance of closure of the PDA, which may be their only source of pulmonary blood flow.

Neonates who are experiencing increased pulmonary blood flow have decreased lung compliance and require higher ventilatory pressures and PEEP in order to maintain adequate V/Q ratios. Higher pulmonary blood pressures are less affected by increases in ventilatory pressures for these neonates. Oxygen should also be cautiously used if the defect involves a necessary PDA. In all cases, RCPs caring for these patients need to be prepared to adjust ventilator settings to compensate for any changes in compliance.

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