Laryngeal muscle activity during nasal high-frequency oscillatory ventilation in nonsedated newborn lambs.
We have previously shown that nasal pressure support ventilation (nPSV) can lead to an active inspiratory laryngeal narrowing in lambs. This, in turn, can limit lung ventilation and divert air into the digestive system, with potentially deleterious consequences. On the other hand, nasal high-frequency oscillatory ventilation (nHFOV) is particularly attractive in newborns, especially since, unlike nPSV, it does not require synchronization with the patient's inspiratory efforts. The main aim of the present study was to test the hypothesis that glottal constrictor muscle activity (EMG) does not develop during nHFOV. A secondary objective was to study laryngeal EMG during nHFOV-induced central apneas. Polysomnographic recordings were performed in 7 nonsedated lambs which were ventilated with increasing levels of nPSV and nHFOV at both 4 and 8 Hz, in random order. States of alertness, diaphragm and glottal muscle EMG, SpO2, and respiratory movements were continuously recorded. While phasic inspiratory glottal constrictor EMG appeared with increasing nPSV levels in 6 out of 7 lambs, it was never observed with nHFOV. In addition, nHFOV at 4 Hz dramatically inhibited central respiratory drive in 4/7 lambs, with 64-100% of recording time spent in central apnea in 3 lambs. No glottal constrictor EMG was observed during these central apneas. nHFOV does not induce glottal constrictor muscle EMG in nonsedated newborn lambs, in contrast to nPSV. This may be an additional advantage of nHFOV relative to nPSV.