Pulse Photoplethysmography Derived Respiration for Obstructive Sleep Apnea Detection

Abstract

Five time series which are known to be modulated by respiration are derived from the pulse photoplethysmographic (PPG) signal, and they are analyzed for obstructive sleep apnea (OSA) detection: Pulse rate, amplitude, and width variabilities (PRV, PAV, and PWV, respectively), pulse upslopes, and slope transit time (STT). A total of 26 polysomnographic recordings were split in 1-min segments which were manually labeled as OSA (653 segments), normal breathing (7204 segments), or other pulmonary events. For each one of the 5 PPG-derived series, 4 features were extracted: the standard deviation, the power at high and low frequency (PLF) bands, and the normalized PLF. These 20 features were used as input of a least-squares support vector machine classifier using an RBF kernel. Results show an accuracy of 72.66%, suggesting that the analyzed features are promising for the detection of OSA from only the PPG signal.

Sleep Apnea Detection Using Pulse Photoplethysmography

“…given in Table 1, is lower than in previous studies in literature. We achieve an accuracy of 68.7 %, whereas in [6] an accuracy of 72.66% was obtained. In this study, however, only obstructive apneas were considered.…”

“…The PPG signals were preprocessed by applying a lowpass filter with a cut-off frequency of 35 Hz [6]. Next, the PPG peaks were detected by applying a linear filtering transformation to emphasize the peak slopes, followed by an adaptive thresholding [5].…”

“…The peak apex point (nA) was extracted, as well as its basal (nB) and mid-point (nM). Moreover, the first derivative of the signal was used to compute the peak onset (nO), end point (nE), and the slope end point (nEs) [6]. From these peak points 6 PPG time series were computed.…”

“…These could be due to subclinical apneas which are too short to be scored according to the AASM rules, or other causes such as movement of the patient. In [6], it was investigated whether these false positives occurred more often during REM sleep, which was not the case. In this study the patients were on average in REM sleep for 14 % of the recordings.…”

“…Since the pulse oximeter used to measure the SpO2 also records the pulse photoplethysmography (PPG) signal, this signal seems to be the first choice to improve the SpO2 based detection. Previous studies have already used the PPG signal for the detection of sleep apnea [5][6], since parameters linked to autonomic arousals and respiration can be extracted from the signal.…”