Detrended Fluctuation Analysis of Oxyhemoglobin Saturation by Pulse Oximetry in Sleep Apnea Syndrome
Variability of oxyhemoglobin saturation during sleep has been utilized as diagnostic index for sleep apnea. This work examined the parameters of a detrended fluctuation analysis (DFA) plot created from series data for oxyhemoglobin saturation during a sleep study in 273 subjects. A novel automated algorithm was devised to measure the parameters of a DFA log–log plot that included the slopes of 4 line segments and the coordinates and angles of their intersections. The diagnostic value of the parameters was investigated by receiver operating characteristic (ROC) curves using apnea/hypopnea index (AHI) cutoff values of 5, 15, and 30. Three of the DFA plot parameters exhibited an area under the ROC curve ≥0.89 for all three AHI cutoff values. Principal component analysis found a surrogate variable that increased the areas under ROC curves to greater than 0.92 for all of the AHI cutoff values. The algorithm was “leave-one-out” cross-validated and validated in another 206 subjects receiving polysomnographic studies. The results demonstrate that the DFA plot of oxyhemoglobin saturation is a useful tool for screening subjects with sleep apnea.