Effects of exchange transfusion on neonatal thyroid function

Abstract

cage. 7 The resultant collapsing chest apparently triggers an inhibitory reflex which suppresses central respiratory drive. Continuous positive airway pressure may reduce rib cage distortion by stabilizing the chest wall, and, thus, may reduce the incidence of apnea by eliminating the intercostal-phrenic inhibitory reflex. ~ Stimulation of lung mechanoreceptors and alteration of sleep states are other possible mechanisms by which continuous positive airway pressure may reduce apnea. Newborn infants have a unique ventilatory response to hypoxemia, that is, a brief increase in ventilation followed by periodic breathing and, occasionally, by apnea? Thus, although apnea may be precipitated by induced hypoxemia,' in our study most episodes of apnea occurred during normal states of oxygenation, and no difference in transcutaneous oxygen could be found between nonapneic periods and periods just prior to apneic attacks. Our findings are consistent with those of Gerhardt and Bancalari) ~ who found no significant difference in Pa% or lung compliance in infants with apnea compared to infants without apnea. Therefore, although hypoxemia such as that resulting from pulmonary disease may exacerbate apneic spells, it does not appear that a low or decreasing Pa% is an important pathogenetic factor in idiopathic apnea of prematurity. Conversely, increasin~ inspired oxygen to infants with no pulmonary disease will decrease the incidence of periodic breathing and apnea and may prevent or ameliorate respiratory muscle fatigue. However, the arterial oxygen tension required for this effect may be hazardous for neonates at risk for retrolental fibroplasia. '1 In our opinion, it is inappropriate to treat apnea with continuous oxygen therapy unless blood gas monitoring reveals a true state of hypoxemia.