I. Kianicka et al., COORDINATION BETWEEN GLOTTIC ADDUCTOR MUSCLE AND DIAPHRAGM EMG ACTIVITY IN FETAL LAMBS IN-UTERO, Journal of applied physiology, 84(5), 1998, pp. 1560-1565
It has previously been reported that; active glottic adduction is pres
ent during prolonged apneas but absent during periods of breathing mov
ements in fetal lambs in utero. The present study was aimed at examini
ng the precise coordination between fetal breathing movements [diaphra
gm electromyographic (EMG) activity (Di EMG)] and glottic adduction [t
hyroarytenoid muscle EMG activity (TA EMG)]. Electrodes for electroenc
ephalogram,, eye movements, TA EMG, and Di EMG and an arterial cathete
r were surgically implanted in fetal lambs 123-142 days postconception
. Polygraphic recordings were performed without sedation while the ewe
breathed room air (n = II) or various gas mixtures (hypoxia, n = 5; h
yperoxia, it = 4; hypercapnia, it = 5; hypercapnia + hyperoxia, n = 5)
. Tonic TA EMC was observed throughout >90% of apneas (>6 s) in both n
on-rapid-eye-movement and rapid-eye-movement sleep, and when Di EMG fr
equency decreased in rapid-eye-movement sleep. In all but two fetuses,
TA EMG was immediately inhibited when Di EMG appeared. Altering blood
gases did not modify these results. In conclusion, Di EMG and TA EMG
are well coordinated in late gestation in fetal lambs, except in a few
cases. These findings may have consequences for understanding the pat
hogenesis of mixed/obstructive apneas of prematurity.