Upper airway muscle activity and upper airway resistance in young adults during sleep.

To determine the relationship between upper airway muscle activity and upper airway resistance in nonsnoring and snoring young adults, 17 subjects were studied during sleep. Genioglossus and alae nasi electromyogram activity were recorded. Inspiratory and expiratory supraglottic resistance (Rinsp and Rexp, respectively) were measured at peak flow, and the coefficients of resistance (Kinsp and Kexp, respectively) were calculated. Data were recorded during control, with continuous positive airway pressure (CPAP), and on the breath immediately after termination of CPAP. Rinsp during control averaged 7 +/- 1 and 10 +/- 2 cmH2O.l-1.s and Kinsp averaged 26 +/- 5 and 80 +/- 27 cmH2O.l-1.s-2 in the nonsnorers and snorers, respectively (P = not significant). On the breath immediately after CPAP, Kinsp did not increase over control in snorers (80 +/- 27 for control vs. 46 +/- 6 cmH2O.l-1.s-2 for the breath after CPAP) or nonsnorers (26 +/- 5 vs. 29 +/- 6 cmH2O.l-1.s-2). These findings held true for Rinsp. Kexp did not increase in either group on the breath immediately after termination of CPAP. Therefore, 1) increases in upper airway resistance do not occur, despite reductions in electromyogram activity in young snorers and nonsnorers, and 2) increases in Rexp and expiratory flow limitation are not observed in young snorers.