Influence of sleep on response to negative airway pressure of tensor palatini muscle and retropalatal airway

Increased retropalatal airway resistance may be caused by a sleep-induced loss of palatal muscle activity and a diminished ability of these muscles to respond to the increasing intrapharyngeal negative pressure that develops during sleep. To investigate these possibilities, in six normal subjects, we determined the effect of non-rapid-eye-movement sleep on 1) the tensor palatini (TP) electromyogram (EMG) response to rapid-onset negative-pressure generations (NPG) in the upper airway and 2) the collapsibility of the retropalatal airway during these NPGs. During wakefulness, the change in TP EMG from basal to peak levels (during NPG) was 19.8 +/- 3.2 arbitrary units (P < 0.005). This was markedly reduced during sleep (3.6 +/- 1.5 arbitrary units; P < 0.001). The latency of the TP EMG response was 48.5 +/- 5.6 ms during wakefulness but was prolonged during sleep (105.0 +/- 12.2 ms; P < 0.02). The peak transpalatal pressure during NPG (a measure of airway collapse) was 2.1 +/- 0.7 cmH2O during wakefulness and increased to 5.3 +/- 0.8 cmH2O during sleep (P < 0.05). We conclude that the brisk reflex response of the TP muscle to negative pressure during wakefulness is markedly reduced during non-rapid-eye-movement sleep, in association with a more collapsible retropalatal airway. We speculate that the reduction in this TP reflex response contributes to retropalatal airway narrowing during sleep in normal subjects.