Thyroarytenoid muscle electrical activity during spontaneous apneas in preterm lambs

Laryngeal dynamics plays a major role during perinatal life, a period of re spiratory control immaturity. Continuous electromyographic (EMC) activity o f a laryngeal adductor muscle (thyroarytenoid [TA] muscle), was recently ob served throughout provoked central apneas, either isolated or during induce d periodic breathing, in full-term lambs. The aim of the present study was to test if continuous TA EMG activity was also present during spontaneous a pneas in nonsedated preterm lambs. We studied 7 premature lambs (term 131 /- 1 d of postconceptional age). Premature birth was induced after accelera tion of fetal lung maturation. Electrodes for diaphragm, inferior pharyngea l constrictor (IPC), and TA electromyograms, electrocardiogram, electroence phalogram, eye movement, and airflow recordings were implanted. Radioteleme try recordings were repeated from 135 to 149 +/- 8 d of postconceptional ag e. A total of 2,088 apneas (2,020 central and 68 mixed) greater than or equ al to 3 s were recorded in the lambs, including 57 epochs of periodic breat hing. Continuous TA EMC activity was present throughout 88.4% of all apneas and 98.4% of apneas during periodic breathing, regardless of the sleep sta ge. These results suggest that active glottic closure is frequent during sp ontaneous central apneas in this model of prematurity. This unique model wi ll allow us to study controlling mechanisms and consequences of glottic clo sure during neonatal apneas.