CPAP ONLY REDUCES NEONATAL APNEA ASSOCIATED WITH ARWAY OBSTRUCTION

Abstract

Although continuous positive airway pressure (CPAP) is an established treatment for apnea of prematurity, its physiologic mechanism of action is unclear. We therefore investigated the effect of CPAP on obstructive, central and mixed apneas, defined by the presence or absence of upper airway obstruction. 14 preterm infants of GA 28 wk (range 26-32) and WT 1156g (range 680-2000g) were studied during sequential 45 min periods on, off, and again on 4 cm H2O CPAP. Ventilation (via nasal mask pneumo-tachometer), HR, chest wall movement, TcPO2 and TcPCO2 were continuously recorded. 252 apneas ⩾5 sec (mean duration 13±19 sec), and 170 apneas ⩾10 sec (mean duration 17±9 sec) were analyzed. CPAP markedly reduced both mixed and obstructive apneas ⩾5 sec and ⩾10 sec. In contrast, central apneas ⩾5 and ⩾10 sec were entirely unaffected by CPAP. Although minute ventilation was not altered, TcPO2 increased by 11±11 mmHg on CPAP, whether or not apnea was present. We conclude that CPAP only relieves apnea with an obstructive component, possibly by splinting the pharyngeal airway, or reflexly activating muscles which maintain upper airway patency in preterm infants. Sponsored by NIH Grant No. HL25830