EFFECT OF SLEEP AND SIGHING ON UPPER AIRWAY-RESISTANCE IN MONGREL DOGS

We investigated the effect of sleep and sighing on supratracheal resis tance in unrestrained mongrel dogs breathing through the nose by compa ring within-breath changes in upper airway pressure-flow relationship in control, sigh, and five postsigh breaths recorded during wakefulnes s and during non-rapid-eye-movement and rapid-eye-movement sleep. A si gh breath was characterized by a high tidal volume and was typically f ollowed by an apnea of a variable duration. Sleep had little or no eff ect on supratracheal resistance, measured at peak flow rates, during q uiet breathing (awake 7.3 +/- 0.4, non-rapid eye movement 8.3 +/- 0.4, and rapid eye movement 6.8 +/- 0.4 cmH(2)0.1(-1).s). The resistance w as identical in the early part of inspiration in control and sigh brea ths but increased during the augmented phase of sigh breaths. Resistan ce at peak inspiratory flow was higher in sigh breaths than in control breaths in all sleep states. The flow-pressure profile of postsigh br eaths was identical to that of control breaths in all sleep states. We conclude that upper airway resistance is essentially unaffected by sl eep state in the mongrel dog and that sighing increases upper airway r esistance regardless of sleep state.