1170 PHARYNGEAL PRESSURE DURING NASAL CPAP

Abstract

The pressure in an infant's airway when CPAP is delivered by nasal prongs has not been previously reported. Using air-filled catheters and differential pressure transducers we have measured simultaneous pressures in nasal prongs (P_pr) and pharynx(P_px) in 18 newborns. After a steady state was achieved, end expiratory pressure in five consecutive breaths was measured: these were usually identical but otherwise were averaged. The pressure difference (P_pr-P_px=ΔP) was low in infants with visual evidence of tight palato-glossal apposition. Though there was much variation, babies whose mouths were a) spontaneously open without tongue/palate seal had a %ΔP=48% ± 4% (weighted average ± SEM), b) spontaneously closed or who had a demonstrable seal had a %ΔP=8% ± 3%; these are significantly different means (p=<.001). In the latter group there was a close correlation between P_pr and P_px (r = 0.965). The ability to maintain a good seal was not related to gestational age, post natal age, severity or type of disease. However, babies who maintained a good seal frequently had an active gag reflex (Fishers exact test p=.04). Spontaneous closure of the mouth usually indicated a good seal but forcible closure did not consistently decrease the pressure drop.

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