ACTIVITY OF RESPIRATORY PUMP AND UPPER AIRWAY MUSCLES DURING SLEEP ONSET

Ventilation decreases at sleep onset. This change is initiated abruptl y at alpha-theta electroencephalographic transitions. The aim of this study was to determine the contributions of reduced activity in respir atory pump muscles and upper airway dilator muscles to this change. Su rface electromyograms over the diaphragm (Di) and intercostal muscles and fine-wire intramuscular electrodes in genioglossus (GG) and tensor palatini (TP) muscles were recorded in nine healthy young men. It was shown that phasic Di and both phasic and tonic TP activities were low er during theta than during alpha activity. Breath-by-breath analysis of the changes at alpha-theta transitions during the sleep-onset perio d showed a number of changes. At alpha-theta transitions, phasic activ ity of Di, intercostal, and GG muscles fell and rose again, and phasic and tonic activities of TP fell and remained at low levels during the ta. With a state transition from theta to alpha, the phasic and tonic activities of the Di, GG, and TP increased dramatically. It is now cle ar that the fall in ventilation that occurs with sleep is related to a fall in activities of both upper airway dilator muscles and respirato ry pump muscles.