I. Kianicka et al., LARYNGEAL AND ABDOMINAL MUSCLE ELECTRICAL-ACTIVITY DURING PERIODIC BREATHING IN NONSEDATED LAMBS, Journal of applied physiology, 84(2), 1998, pp. 669-675
We recently reported that glottic closure was present throughout centr
al apneas in awake lambs. The present study tested whether glottic clo
sure was also observed during periodic breathing (PB). We attempted to
induce PB in 21 nonsedated lambs on return from hypocapnic hypoxia to
room air. Airflow and thyroarytenoid (a laryngeal constrictor, n = 16
), cricothyroid (a laryngeal dilator, n = 10), and abdominal (n = 9) m
uscle electrical activity (EMG) were monitored continuously. PB was ob
served in 16 lambs, with apneic phases in 8 lambs. Thyroarytenoid musc
le EMG was observed at the nadir of PB, either throughout apnea or wit
h prolonged expiration during the lowest respiratory efforts. Phasic i
nspiratory cricothyroid muscle EMG and phasic expiratory abdominal EMG
disappeared at the nadir of PB. Active glottic closure at the nadir o
f PB, without abdominal muscle contraction, could be a beneficial mech
anism, preserving alveolar gas stores for continuing gas exchange duri
ng the apneic/hypopneic phase of PB. However, consequences of active g
lottic closure on ventilatory instability, either enhancing or reducin
g, are unknown.