Cepstrum feature selection for the classification of Sleep Apnea-Hypopnea Syndrome based on heart rate variability

Cepstrum Coefficients are analyzed in order to study its performance in Sleep Apnea Hypopnea Syndrome (SAHS) screening. A forward feature selection technique is applied in order to know for one thing, what cepstrum parameters can extract better information about the influence of breath sleep disorder on the heart rhythm, and on the other hand, trying to detect apneas based on the RR series obtained from the electrocardiogram (EKG). 70 ECG recordings from Computers in Cardiology Challenge 2000 are divided into a learning set and a test set of equal size. Each set consists of 35 recordings, containing a single ECG signal. Each recording includes a set of reference annotations, one for each minute, which indicates the presence or absence of apnea during that minute. These reference annotations were made by human experts on the basis of a complete polysomnography. Statistical classification methods based on Linear Discriminant Analysis (LDA) and Quadratic Discriminant Analysis (QDA) are applied to the classification of sleep apnea epochs. LDA presents a sensitivity of 64.1% and specificity of 90.2% (auc=0.87). QDA presents a sensitivity of 73.7% and specificity of 85.9% (auc=0.89). In both cases, contribution of the 4th coefficient related to Respiratory Sinus Arrhythmia plays an important role in SAHS detection.