EFFECT OF SLEEP ON CHANGES IN BREATHING PATTERN ACCOMPANYING SIGH BREATHS

We studied the effect of sleep on the characteristics of sigh breaths and the associated changes in breathing pattern in breaths following s pontaneous sighs in 4 unrestrained dogs with an intact upper airway. T he sigh breath was characterized by its large tidal volume (VT), long TI and TE in comparison with the control breath. The volume of the sig h breath was larger in awake sighs than in those recorded during non-R EM (NREM) and REM sleep. The strength of Hering-Breuer reflex as deter mined by duration of the post-sigh apnea was similar in NREM and REM s leep. Sighs occurring during wakefulness, NREM and REM sleep were asso ciated with augmented activity of the parasternal muscles during inspi ration, and a persistent tonic abdominal muscle activity during the ex piratory period. Breathing pattern in the post-sigh period was charact erized by a smaller VT and longer TE in the first post-sigh breath in all sleep states (compared with the control breath), but the pattern r eturned to control level within the second or third post-sigh breath i n both NREM and REM sleep. Sighs did not precipitate periodic breathin g or other forms of abnormal breathing patterns in either wakefulness or sleep. We conclude that the respiratory control mechanisms stabiliz ing breathing after a sigh in the awake dog are intact in NREM and REM sleep.