A mobile system for precise wireless pulse transit time (PTT) monitoring

The pulse transit time (PTT) is a parameter which can be used to characterize the functional state of the cardiovascular system. The PTT, which is closely connected to the blood pressure, can be derived from an electrocardiogram (ECG) and a simultaneously recorded photoplethysmogram (PPG) signal. In contrast to conventional non-invasive blood pressure measurements, the PTT can be calculated quasi continuously, giving instant feedback to condition changes. Many proposed systems use cables to connect ECG and PPG sensors. This is sufficient for stationary applications. This paper presents a system for wireless PTT measurements that permits patient mobility and thus makes new application scenarios possible. The main challenge of wireless time synchronization, necessary for precise PTT results, is solved using the IEEE 802.15.4 beacon enabled mode.