Analysis of nocturnal pulse oximetry in sleep medicine

Oxygen saturation obtained from nocturnal pulse oximetry is a significant evaluation parameter for sleep related breathing disorders, especially in the diagnosis of the obstructive sleep apnea syndrome (OSA). Today clinical interpretation relies mainly on the number of desaturation events per hour (oxygen desaturation index, ODI). In this study various alternatives were established and their applicability for OSA screening was evaluated. The discussed methods include time-based approaches (Δ-index), non-linear analysis (central tendency measure, approximate entropy), and spectral methods (Welch transform, wavelet transform). When applied to 192 data sets (132 male, 60 female, 47.9±15.5 years, BMI 27.4±6.5 kg/m(2)) these methods showed good correlation with clinical findings. When discriminating between non-OSA and OSA patients the approaches under investigation yield sensitivity values between 96.6% and 100% and specificity values between 97.4% and 100%. Particularly spectral methods could provide parameters for an optimized OSA screening based on nocturnal pulse oximetry.