Randomised prospective parallel trial of therapeutic versus subtherapeuticnasal continuous positive airway pressure on simulated steering performance in patients with obstructive sleep apnoea

Background-Obstructive sleep apnoea (OSA) impairs vigilance and may lead to an increased rate of driving accidents. In uncontrolled studies accident r ates and simulated steering performance improve following treatment with na sal continuous positive airway pressure (NCPAP). This study seeks to confir m the improvement in steering performance in a randomised controlled trial using subtherapeutic NCPAP as a control treatment. Methods-Fifty nine men with OSA (Epworth Sleepiness Score (ESS) of greater than or equal to 10, and greater than or equal to 10/h dips in Sao, of >4% due to OSA) received therapeutic or subtherapeutic NCPAP (approximate to 1 cm H2O) for one month. Simulated steering performance over three 30-minute "drives" was quantified as: standard deviation (SD) of road position, deter ioration in SD across the drive, length of drive before "crashing", and num ber of off-road events. The reaction times to peripheral target stimuli dur ing the drive were also measured. Results-Subtherapeutic NCPAP did not improve overnight >4% Sao, dips/h comp ared with baseline values, thus acting as a control. The SD of the steering position improved from 0.36 to 0.21 on therapeutic NCPAP, and from 0.35 to 0.30 on subtherapeutic NCPAP (p = 0.03). Deterioration in SD of the steeri ng position improved from 0.18 to 0.06 SD/h with therapeutic NCPAP and wors ened from 0.18 to 0.24 with subtherapeutic NCPAP (p = 0.04). The reaction t ime to target stimuli was quicker after therapeutic than after subtherapeut ic NCPAP (2.3 versus 2.7 seconds, p = 0.04). Conclusions-Therapeutic NCPAP improves steering performance and reaction ti me to target stimuli in patients with OSA, lending further support to the h ypothesis that OSA impairs driving, increases driving accident rates, and t hat these improve following treatment with NCPAP.