Development of Lead System for ECG-Derived Respiration Aimed at Detection of Obstructive Sleep Apnea Syndrome

Obstructive sleep apnea syndrome is the most common type of sleep apnea, characterized by repetitive pauses in breathing during sleep. Recent studies have investigated screening methods based only on an electrocardiogram (ECG). Generally, in ECG-based screening, the ECG-derived respiration (EDR) is often used, which is caused by the variance in the cardiac electrical axis due to the chest movement associated with the respiration itself. This method might be effective for diagnosing the sleep apnea severity, called the apnea-hypopnea index, which is defined by the duration and occurrence rate of apnea episodes. However, conventional ECG lead systems are not necessarily optimized for this purpose. In this study, nine bipolar electrodes located across the entire ventral thoracic region were devised, based on the conventional lead system, to effectively measure thoracic breathing. To evaluate the most effective electrode placements, two eupneic and three apneic tasks with nine electrodes were conducted, and EDRs were calculated. Then, the respiratory rates were estimated from the EDRs, and the eupnea and apnea groups were classified using features of the EDRs. Consequently, it was found that three electrodes located at the lower thoracic region yielded accurate estimations of the respiratory rate and discrimination rate.