Spectral Analysis of ECG Ventricular Waveform Parameters in Obese Sleep Apnea Patients

Obstructive Sleep Apnea/Hypopnea Syndrome (OSAHS) is a serious sleep disorder in which partial or complete blockage in the upper airway causes reduction or cessation of breathing with continuous respiratory effort. Hypoxemia and hypercapnia accompanying OSAHS events are correlated with changes in the cardiovascular response and in particular, the electrocardiogram (ECG). Temporal and spectral changes in ECG waveforms, namely corrected QT interval (QTc), ST-segment, and T-wave duration, have been highly correlated with apneic breathing. In this study, ECG recordings, marked by an accredited sleep technician, obtained from five obese patients diagnosed with sleep apnea (Aged $35.6\pm 8.3$ years, BMI $52.4\pm 8.9\text{kg}/\mathrm{m}2$, AHI $14.6\pm 8 \text{events}/\text{hr})$ were analyzed (a total of 56 15-minute ECG records). Of the recordings, 29 did not contain any apneic events. The remaining 27 recordings included events with an average of $8.2\pm 4.7$ events per recording. QTc intervals, ST-segments, and T-wave durations were extracted from each beat in these records. Spectrograms of the QTc records indicate a continuous power band around 0.3 Hz in the uneventful record, correlating with a continuous breathing pattern modulation of the QTc signal. Furthermore, separately comparing QTc to T-Wave durations and ST-segments in certain frequency bands show significant differences between eventful versus uneventful records $(\mathrm{p} <$ 0.05) that can be used to automatically classify apneic ECG records.