# Detection of Sleep Apnea from Electrocardiogram and Pulse Oximetry Signals Using Random Forest  
[PERSON]  
1 School of Life and Environmental Sciences, Guilin University of Electronic Technology, Guilin 541004, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (A.Z. ); [EMAIL_ADDRESS] (Q.G. ); zhujuyu85994163.com (Y.Z. ); [EMAIL_ADDRESS] (J.H.) [PERSON]  
1 School of Life and Environmental Sciences, Guilin University of Electronic Technology, Guilin 541004, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (A.Z. ); [EMAIL_ADDRESS] (Q.G. ); zhujuyu85994163.com (Y.Z. ); [EMAIL_ADDRESS] (J.H.) [PERSON]  
1 School of Life and Environmental Sciences, Guilin University of Electronic Technology, Guilin 541004, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (A.Z. ); [EMAIL_ADDRESS] (Q.G. ); zhujuyu85994163.com (Y.Z. ); [EMAIL_ADDRESS] (J.H.) Junxiang Huang  
1 School of Life and Environmental Sciences, Guilin University of Electronic Technology, Guilin 541004, China; [EMAIL_ADDRESS] (J.Z. ); [EMAIL_ADDRESS] (A.Z. ); [EMAIL_ADDRESS] (Q.G. ); zhujuyu85994163.com (Y.Z. ); [EMAIL_ADDRESS] (J.H.) [PERSON]  
Guilin 541004, China;  
Footnote 1: email: {Zhuj, 2, 4218, 42  
wearing too many sensors during physiological signal collection can cause discomfort to the patient. In addition, the diagnosis of OSA requires sleep specialists to spend a lot of time manually analyzing PSG data [7]. Therefore, automatic detection of SA using fewer signals is necessary. Researchers have typically developed SA detection algorithms using ECG signals. ECG is a non-invasive technique for recording the electrical activity of heart and the physiological activity of heart is regulated under the autonomic nervous system (ANS). Studies have shown that hypoxia caused by SA can lead to the dysregulation of the ANS. Clinically, heart rate variability (HRV) is an important indicator of the outcome of ANS regulation [8]. Therefore, it is feasible to screen for apnea by monitoring ECG during sleep [9]. Yet, ECG signals are easily influenced by cardiovascular disease status. This makes the diagnosis of SA more challenging. Apart from ECG signals, SpO2 signals are also widely used to detect SA as the lack of airflow due to SA events can lead to a decrease in SpO2. Repetitive oxygen desaturation is highly specific for apnea. However, the sensitivity of oximetry is usually low, as not all apnea events lead to discernible desaturations [7]. Thus, SpO2 alone or ECG alone can be used as a potential diagnostic means of SA, but not as a reliable means. With technological advances in sensors and low-power embedded systems, the collection of physiological signals has become easier and more economical [10]. Therefore, we consider using multiple signals to develop a more reliable detection algorithm of SA, rather than being limited to a single signal. This study explores the efficiency and reliability of a multimodal approach to the automated detection of SA events using a combined channel of ECG and SpO2. To this end, we extracted features from ECG signal and SpO2 signal separately, and then fused the features of the two different modalities. Feature selection was performed using the recursive feature elimination with cross-validation (RFECV) algorithm. Then, the selected features were fed to the RF classifier to identify sleep apnea events. Our study provides three main contributions to research. First, we verify the complementarity of ECG and SpO2 signals to automatically detect SA. When the two signals are combined, the diagnostic ability is increased. Second, the RFECV algorithm is employed to select the most important features. The proposed SA detection technique uses a smaller number of features and is computationally inexpensive compared to most of the existing methods. Third, we enrich the method in the field of the automated detection of SA by applying a multimodal approach to fuse ECG and SpO2 signals at the feature level. So far, most of the extant literature primarily used SpO2 alone or ECG alone, but did not consider the combination of ECG and SpO2.