Ventilation during sleep onset in young adult females.

Ventilation is known to decrease from wakefulness to non-rapid-eye-movement sleep. In males, the change is associated with the commencement of theta activity in the electroencephalogram (EEG). The magnitude of the decrease is greater than that required by the reduction in metabolic rate at sleep onset and it has been suggested that the nonmetabolic component reflects the loss of a wakefulness drive to respiration. The effect of sleep onset on ventilation in female subjects was of interest because previous studies on changes in respiratory activity during sleep in this population have produced inconsistent results, a phenomenon that may relate to the menstrual cycle and the role of progesterone in respiratory activity. The present experiment sought to investigate ventilation during sleep onset in young adult females as a function of the menstrual cycle, and to compare the results with data collected from male subjects in an earlier experiment. Sleep onset was studied in five subjects in a series of single subject designs. The data were consistent with those of the male subjects and showed decreases in ventilation associated with the onset of theta activity in the EEG. Furthermore, no menstrual phase differences were apparent. The results indicate that in females, as in males, sleep is associated with loss of a wakefulness drive to ventilation.