Approximate Entropy from Overnight Pulse Oximetry for the Obstructive Sleep Apnea Syndrome

The aim of this preliminary study was to asses whether a time series analysis from overnight pulse oximetry by means of approximate entropy (ApEn) could yield essential information on the diagnosis of obstructive sleep apnea (OSA) syndrome. We analyzed the oxygen saturation (SaO
₂
) signals of 74 patients (44 with a positive diagnosis of OSA and 30 with a negative diagnosis of OSA) by means of ApEn, which quantified the regularity (or complexity) of time series. Results showed that recurrence of apnea events in patients with OSA determined a significant increase in ApEn values with a mean plusmnstandard deviation (SD) of 1.07 plusmn 0.30. A mean plusmn SD ApEn value of 0.47 plusmn 0.25 was estimated in patients without OSA. We obtained an area under the ROC curve of 0.94. The optimum threshold was selected at 0.81, where we achieved a 79.5% sensitivity and 90% specificity. Further analyses are necessary with new and larger data set to test the potential value of our methodology prospectively