Monitoring of heart rate, blood oxygen saturation, and blood pressure using a smartphone

Smartphones can be used as multifunctional devices for instant monitoring of the users' health. In this study, we proposed methods for the estimation of heart rate (HR), blood oxygen saturation (SpO2), and blood pressure (BP). Two smartphone sensors were used for data recording: the rear camera and the microphone. Our approach for HR and SpO2 estimation was based on creating a photoplethysmogram (PPG) from the camera data. SpO2 estimation was improved and the smartphone quantum efficiency did not have to be known. BP was estimated using the pulse transit time value calculated from the PPG and phonocardiogram (PCG) recorded using the microphone. Fifty records (for HR and SpO2) and 15 records (for BP) were sensed and used for training and testing purposes. An Android (TM) application was developed to provide audio-visual feedback to the measured subject, to indicate whether the placement of the smartphone was appropriate to provide signals of sufficient quality for BP estimation. The mean absolute errors (MAE) were 1.1% for SpO2 and 1.4 beats per minute (bpm) for HR estimation using the testing dataset. MAE of systolic and diastolic BP were 5.1 mmHg and 7.5 mmHg, respectively. The possibility of using the smartphone as a fast alternative to conventional and specialized devices for SpO2, HR, and BP estimation was statistically proven.