Photoplethysmography is an easy non-invasive method to detect the pulse wave amplitude (PWA) from a finger. This can be measured using the Somnocheck micro system. A pulse wave amplitude decrease (PWAD) is considered to be a marker for autonomic activation. Detecting the PWAD is a surrogate marker for waking reactions (arousal) which eventually will contribute to assess sleep disruption and resulting performance deterioration. Arousal and performance deterioration and its possible improvement under continuous positive airway pressure (CPAP) therapy will be determined in this study.

Patients from the sleep laboratory with verified obstructive sleep apnea syndrome (OSAS) will be asked to participate in this study.

A device is used to determine autonomic arousal over night (SOMNOcheck micro). The Somnocheck micro records oxygen saturation as well as pulse frequency and breathing, and calculates an autonomic arousal index (AAI). Somnocheck measurements will take place in two nights (baseline and with CPAP) and parallel to a standard polysomnography (PSG). The PSG provides data to analyze the arousal frequency according to ASDA rules, which will then be compared to the AAI.

Performance is determined twice (prior and after CPAP therapy) by the use of a steering simulator programme (DASS). Differences in arousal will be correlated with differences in performance (deviation from the road, reaction time). The subjects are also asked to fill out the Epworth Sleepiness Scale (ESS) twice, prior and after therapy. Aim is to compare Somnocheck and PSG measurements and daytime sleepiness with DASS and ESS.

Inclusion Criteria:

• Obstructive Sleep Apnea (AHI >5)

Exclusion Criteria:

• Suspected acute cardiac, pulmonary or neurologic disease