Systolic blood pressure estimation using Android smart phones

Systolic blood pressure (SBP) is one of the important vital signs that need to be monitored for personal healthcare. Measuring SBP via pulse wave transit time (PWTT) requires monitoring ECG and pulse wave signals simultaneously, which has no portability. And before the measurement the parameters indicating the relationship between BP and PWTT must be calculated through training. This paper describes a portable method developed by the authors to measure SBP from PWTT using one Android smart phone. Volume pulse waves were acquired by a smart phone with its built-in camera, and then accelerated pulse waves were gotten through filtering, amplifying and processing the signals. The PWTT between the progressive and reflected waves of the accelerated pulse waves was calculated. The tester swayed his arm with hand holding the same phone to change the SBP for the training. The displacement of the hand was calculated through the accelerometer of the smart phone. Experimental results indicated that there is no obvious difference between SBP measured by the new system and by an electronic sphygmomanometer with error less than 10mmHg.