Portable non-invasive blood pressure measurement using pulse transmit time

Abstract

The conventional method of blood pressure measurement in hospitals uses a cuff that inflates on an arm and causes slight pain on the patient. An alternate device that eliminates this consequence is proposed. Plethymography is the measure of change in blood volume due to blood pressure. Photoplethymography (PPG) uses optical sensors to measure this changes in volume. From PPG, we can derive pulse transit time (PTT), the time difference of two pulses from different sites. We can also directly derive from PPG the heart rate. PTT has been strongly correlated to blood pressure. A mathematical model has been derived and presented to show the relationship of blood pressure and PTT. After testing the device, heart rate and blood pressure data were gathered from the device and the same kind of data was gathered from a conventional blood pressure and heart rate measuring device to act as actual values. These sets of data were compared with each other using the T-test method. Upon applying the treatment, all three two-tail P values are greater than 0.05 which means that the null hypothesis that there is no difference in the results obtained from the two vital signs measuring systems fails to be rejected which means that the proposed system can used as an alternative to the conventional system.