The effect of polysomnography on sleep position: possible implications on the diagnosis of positional obstructive sleep apnea.

This prospective study was designed to determine if physical constraint due to the polysomnography (PSG) apparatus affects PSG results by inducing subjects to sleep in the supine position. Twelve patients found to have positional obstructive sleep apnea (OSA) during standard PSG returned for two additional nights of study during which no PSG leads were attached. The time spent supine was 56% greater during the PSG night than the non-PSG nights, 195 +/- 88.6 min during the baseline PSG and 125 +/- 84.6 min during the non-PSG nights (p < 0.05). Therefore, PSG may overestimate the severity of OSA in some patients with positional OSA.