One night's CPAP withdrawal in otherwise compliant OSA patients: marked driving impairment but good awareness of increased sleepiness

PURPOSE. OSA patients effectively treated by and compliant with CPAP occasionally miss a night’s treatment. The purpose of this study was to use a real car interactive driving simulator to assess the effects of such an occurrence on the next day’s driving, including the extent to which these drivers are aware of increased sleepiness. METHODS. 11 long-term compliant CPAP treated 50-75y male OSA participants completed a 2h afternoon, simulated, realistic monotonous drive in an instrumented car, twice, following one night: i) normal sleep with CPAP ii) nil CPAP. Drifting out of road lane (‘incidents’), subjective sleepiness every 200sec and continuous EEG activities indicative of sleepiness and compensatory effort were monitored. RESULTS. Withdrawal of CPAP markedly increased sleep disturbance, and led to significantly more incidents, a shorter ‘safe’ driving duration, increased alpha and theta EEG power and greater subjective sleepiness. However, increased EEG beta activity indicated more compensatory effort was being applied. Importantly, under both conditions there was a highly significant correlation between subjective and EEG measures of sleepiness, to the extent that participants were well aware of the effects of nil CPAP. CONCLUSIONS. Patients should be aware that compliance with treatment every night is crucial for safe driving.