This paper investigates the specific contributions of the pre-ejection period (PEP) and pulse transit time (PTT) for blood pressure estimation based on the pulse wave methodology. We show that in short-term physical stress tests, PEP dominates PTT variations raising the question of a suitable blood pressure calibration. A model using a generalized pulse wave velocity achieves acceptable accuracy for systolic blood pressure estimation, given our experimental conditions

There is an unmet need for cuff-less blood pressure (BP) monitoring especially, in personal healthcare applications. The pulse arrival time (PAT) approach might offer a suitable solution to enable comfortable BP monitoring even at beat-level. However, the methodology is based on hemodynamic surrogate measures, which are sensitive to patient activities such as posture changes, not necessarily related to blood pressure variations. In this paper, we analyze the impact of posture on the PAT measure and related hemodynamic parameters such as the pre-ejection period in well-defined procedures. Additionally, the PAT of a monitored subject is investigated in an unsupervised scenario illustrating the complexity of such a measurement. Our results show the failure of blood pressure inference based on simple calibration strategies using the PAT measure only. We discuss opportunities to compensate for the observed effects towards the realization of wearable cuff-less blood pressure monitoring. These findings emphasize the importance of accessing context information in personal healthcare applications, where vital sign monitoring is typically unsupervised.

This paper describes an unobtrusive IEEE 802.15.4-based wireless body sensor network (BSN) that enables continuous cuff-less blood pressure monitoring, opening up new perspectives for hypertension diagnosis and treatment, cardio-vascular event detection, and stress monitoring. We estimate the arterial blood pressure based on the pulse arrival time (PAT), which is measured with a waist electrocardiogram (ECG) and an ear photo-plethysmogram (PPG). The PAT measurement requires the synchronization of the wireless sensors' clocks. This is achieved with the flooding time synchronization protocol (FTSP). The evaluation of both the implemented time synchronization and the robustness of the wireless data transmission yielded promising results. Future work will include the study of packet collisions in synchronized IEEE 802.15.4 networks, the enhancement of the BSN with additional context-providing sensors (e.g. accelerometer, magnetometer, thermistor), and the integration of the blood pressure estimation algorithm in a wireless sensor unit.

This paper presents a handheld miniaturized sensor embodiment that allows simultaneous measurement of the electrical and related mechanical cardio-vascular activity. Mechanical motion is detected with a continuous wave Doppler radar sensor and interpreted with a synchronously detected ECG. The patient's posture and activity is measured using accelerometers. Challenges of the current technical approach are the positioning of the sensors, the influence of posture and the correct interpretation of the signals. The Doppler signals are compared with phonocardiography measurements, with a focus on the challenges of this technique. There is still research in an improved modeling of the sensor setup and signal interpretation required.

Blood pressure regulation failures cause neurally mediated syncope often resulting in a fall. A warning device might help to make patients aware of an impending critical event or even trigger the patient to perform countermeasures such as lying down or isometric exercises. We previously demonstrated that the Pulse Arrival Time (PAT) methodology is a potential approach to enable early detection of impending faints. The aim of the present study was to evaluate whether PAT can be used as an easy to measure beat-to-beat surrogate for systolic blood pressure (SBP) changes during a passive standing exercise (head-up tilt table testing (HUTT)). A significant PAT increase of more than 10 % was accompanied with a critical SBP decrease in syncope patients. Although PAT is in general not considered as a good measure of absolute blood pressure we found strong correlations (R>;0.89, P<;0.01) of SBP and PAT after PAT began to increase. Therefore, our data suggest that the pulse arrival time is useful to monitor blood pressure changes in patients with neurally mediated syncope. This might open up new avenues to prevent falls in these patients.