ALL NEONATES ARE NOT OBLIGATE NOSE BREATHERS

Abstract

Unlike adults, neonates are considered obligate nose breathers, hence entirely dependent on a patent nasal airway for ventilation. To fully explore their respiratory response to nasal obstruction, we simultaneously monitored nasal and oral ventilation during sleep and in response to multiple 15 sec nasal occlusions. Ten healthy term infants (mean BW 3600±190g, age 1.7±0.6 d) were studied for 60 min periods. Nasal and oral airflow (via two resistance-matched pneumotachometers), heart rate (HR), TcPO2 PetCO2 and sleep state were continuously recorded.Five of 10 infants initiated and sustained effective oral breathing without arousal during 36±32% of occlusions independent of sleep state. In these infants, arousal occurred during 31±27% of occlusions, and no response in 34±23%. In the remaining 5 infants who did not exhibit oral breathing, arousal occurred in 42±34%, and no response in 58±34% of occlusions. Once begun (within 0-6 sec) oral breathing could be sustained for at least 1 min of continuing nasal occlusion. Tidal vol., resp. rate, HR, TcPO2 and PetCO2 did not change when oral breathing occurred during nasal occlusion, although minute ventilation decreased from 265 to 199 cc/min/kg, p<0.05. Moreover, two of 10 infants exhibited spontaneous combined nasal/oral ventilation while in undisturbed sleep. These results clearly demonstrate that not all infants are obligate nose breathers. Effective oral ventilation can now be included among the neonate's physiologic defenses against life threatening nasal obstruction.