CHANGES IN AIRWAY-RESISTANCE DURING SLEEP ONSET

Ventilation is lower during sleep than wakefulness. An increase in air way resistance has been proposed as the critical factor. As the change in ventilation has been shown to occur abruptly at transitions betwee n alpha and theta electroencephalogram activity, it was of interest to determine whether the increase in airway resistance between wakefulne ss and sleep also occurs at these transitions. Three young healthy mal e subjects were run for an average of 15 sleep onsets in each of three conditions. The three conditions were 1) an esophageal balloon was pu t in place to allow the measurement of airway resistance, 2) in additi on to an esophageal balloon the nose was occluded, and 3) there was no esophageal balloon and the nose was not occluded. Ventilation and air way resistance were measured during sleep onset and analyzed as a func tion of arousal state. In those conditions of the experiment in which airway resistance was affected by state, the changes, like those in ve ntilation, occurred at transitions between alpha and theta electroence phalogram activity. However, in the three subjects studied, the magnit ude of ventilatory changes at alpha-theta transitions and the extent t o which changes in ventilation were associated with changes in airway resistance differed between subjects. It was concluded that although i nspiratory airway resistance is a major component affecting the state- related changes in ventilation at sleep onset, the degree of its contr ibution may vary over individuals.