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

STUDY OBJECTIVE

To test the hypothesis that the change of body and head position affects upper airway patency during midazolam sedation.

DESIGN

Clinical study using 30 healthy subjects.

SETTING

Research unit for sleep study.

INTERVENTIONS

We 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 degrees elevation, and 30 degrees 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).

MEASUREMENTS

The 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 RESULTS

In experiment 1, 30 degrees elevation of the body significantly decreased Pcrit (P < 0.05) to -13.3 +/- 1.3 cm H(2)O compared with -8.2 +/- 1.4 cm H(2)O in supine condition without changing the slope (1/Rua). In experiment 2, head extension significantly decreased Pcrit (-12.5 +/- 1.3 cm H(2)O) (P < 0.05) compared with the value (-8.2 +/- 1.0 cm H(2)O) in supine condition without changing the slope (1/Rua).

CONCLUSIONS

Our findings indicate that 30 degrees 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.