Abstract
We investigated the relationship between optical BCG and ECG signals measured simultaneously for the same heartbeat cycles. Despite the long history of BCG, earlier studies compared BCG and ECG features across large time cycles (inter-heartbeat), but not within the heartbeat cycle (intra-heartbeat). The non-invasively derived BCG signal was found to have a remarkable relationship with the arterial pressure signal, which has not been previously reported. We achieved synchronization of the two disparate modalities to within an estimated uncertainty of 50-70 ms, which allowed us to compare features within the heart cycle (which may be related to the arterial pressure) for one pathological and four healthy subjects lying supine, and found it consistent regardless of their breathing condition, gender and health status. Although not a one-to-one correlation, we show optical BCG proves to be a convenient and an unobtrusive and complementary modality to monitor cardiac activity alongside the well-established ECG.