Browsing by Subject "Pulse transit time"

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Open Access
A proof-of-concept wearable photoplethysmography sensor-node for near real-time pulse transit time measurements
(IEEE, 2017-10) Hırlak, Kenan Çağrı.; Eryılmaz, Zübeyr Furkan; Korkmaz, Makbule Kübra; Töreyin, H.
Use of pulse transit time for estimating blood pressure is a promising method that could potentially address the pressing need for an unobtrusive and continuous blood pressure measurement technique. In this paper, we present a novel wearable smart sensor-node system that captures and transmits the distal timing information of pulse waves to a remote location for near real-time pulse transit time measurements. The proof-of-concept system monitors photoplethysmography signals captured from finger, identifies the foot-points of the waveforms, and transmits the timing information of the foot-points to a receiver over a free-space optical channel. Measurements from one healthy subject show that the average time difference between the distal timing information received in near real-time and calculated off-line is 34±6.2 ms. Supplied by a single 5 V power supply, the proof-of-concept system consumes 190 mW.
Open Access
Quantifying the effects of blood pressure changes on ballistocardiogram signals
(IEEE, 2017) Javaid, A. Q.; Töreyin, Hakan; İnan, Ö. T.
Quantifying the effects of blood pressure (BP) changes on the ballistocardiogram (BCG) signal shape and features can potentially improve the understanding of this mechanical modality of cardiovascular sensing. BCG, a measure of body movements caused by ejection of blood into the vasculature, has recently re-emerged as a promising method for trending cardiac output and myocardial contractility. Although recent research has shown that the BCG waveform has the potential to be used as a viable proximal timing reference for measuring pulse transit time (PTT) and indirectly BP, it has not been deeply explored for direct estimation of BP. In this paper, we posit that the BCG signal contains features corresponding to changes in BP. To further investigate this hypothesis, BCG waveforms were measured using a modified-weighing scale from 14 subjects performing an isometric handgrip challenge in a seated position. The energy in the latter half of the BCG heartbeat was estimated using polynomial fitting and interpolation methods. The results indicate that an increase in mean arterial pressure (MAP) or a decrease in PTT manifests itself in the form of high amplitude oscillations following the main peak (J-peak) in a BCG heartbeat, thus elucidating the mechanisms behind these oscillations and also potentially improving the breadth of data that can be sensed using BCG signals.