EFFECTS OF GENIOGLOSSAL RESPONSE TO NEGATIVE AIRWAY PRESSURE ON UPPERAIRWAY COLLAPSIBILITY DURING SLEEP

Continuous negative airway pressure (CNAP) trials can be used to measu re upper airway (UA) collapsibility. This procedure can be accompanied by an increase in UA muscle activity. The purpose of this study was t o evaluate the influence of CNAP-induced increase in genioglossal (GG) activity on UA collapsibility in 10 healthy sleeping men. UA collapsi bility was measured on two occasions; each recording was preceded by t he administration of a placebo or diazepam (0.15 mg/kg) in a randomize d double-blind crossover design. In seven subjects, the decrease in ma sk pressure (P-mask) was associated with an increase in mean GG electr omyographic (EMG) activity during the placebo trial, with a significan t negative relationship between these two variables. This relationship was still observed with diazepam. In six subjects, the slope of the r elationship between mean EMG and P-mask was less negative with diazepa m. This was associated with an increase in critical pressure (P-crit). With the placebo, a positive relationship was found between P-crit an d the slope of the mean EMG/P-mask relationship. We conclude that P-cr it is influenced by the GG response to the decrease in P-mask during C NAP.