The effects of head and body positioning on upper airway collapsibility in normal subjects who received midazolam sedation

Study ObjectiveTo test the hypothesis that the change of body and head position affects upper airway patency during midazolam sedation.DesignClinical study using 30 healthy subjects.SettingResearch unit for sleep study.InterventionsWe used a pressure-flow relationship to evaluate critical closing pressure (Pcrit) and upper airway resistance (Rua) in different condition of body and head position. A pressure-flow relationship was obtained in 3 body postures (supine, 15° elevation, and 30° elevation) and was obtained in 3 head positions (supine with the head in the neutral, supine with head extension, and supine position with head rotated).MeasurementsThe pressure and inspiratory flow at subjects' nose mask were recorded. Polysomnographic parameters (electroencephalograms, electrooculograms, submental electromyograms, upper esophageal pressure, and plethysmogram) were also recorded.Main ResultsIn experiment 1, 30° elevation of the body significantly decreased Pcrit (P < 0.05) to −13.3 ± 1.3 cm H2O compared with −8.2 ± 1.4 cm H2O in supine condition without changing the slope (1/Rua). In experiment 2, head extension significantly decreased Pcrit (−12.5 ± 1.3 cm H2O) (P < 0.05) compared with the value (−8.2 ± 1.0 cm H2O) in supine condition without changing the slope (1/Rua).ConclusionsOur findings indicate that 30° body elevation and head extension significantly decreased upper airway collapsibility during midazolam sedation and established the relative potency of maneuvers that maintain upper airway patency.