Cuff-Less Blood Pressure Monitoring System Using Smartphones

Abstract

Recently, smartphones with mobile health applications have become promising tools in the healthcare industry due to their convenience, ubiquity for patients, and the ability to gather data in real time. In this paper, we propose a novel non-invasive, portable, and cuff-less method for monitoring BP by only using the smartphones' camera. Our experiment uses pulse transit time (PTT) between two separate photoplethysmogram (PPG) signals to estimate the subjects' systolic blood pressure (SBP) and diastolic blood pressure (DBP). Our proposed method first measures the subject's PPG signals from his/her index fingers using the smartphones' camera. Then, filtering and peak detection algorithms of the proposed method reduce the motion and noise artifacts in the PPG signals. Finally, the proposed method estimates SBP and DBP based on a linear regression model which was trained and tested on 30 trials with six healthy subjects. We evaluated the proposed method by comparing BP values of the proposed method with those of the reference (or gold-standard) device in terms of mean absolute error (MAE), standard deviation of error (SD), and R-squared (R 2) value of the cross-validation. Experimental results show that the proposed method estimates the average of MAE ± SD is 2.07 ± 2.06 mm Hg for SBP estimation, and 2.12 ± 1.85 mm Hg for DBP estimation. These estimates are lower than accurate BP estimation standard (5 ± 8 mmHg). INDEX TERMS Hypertension, blood pressure, cuff-less, smartphone, photoplethysmogram (PPG), pulse transit time (PTT).

Single-Channel Impedance Plethysmography Neck Patch Device for Unobtrusive Wearable Cardiovascular Monitoring

“…We compared the proposed cardiovascular device with recent works, as shown in Table 1 [2], [7], [17]- [21]. The number of recruited subjects was comparable with most works to prove the concept for cardiovascular monitoring.…”

“…Furthermore, the one-step calibration algorithm was applied in continuous BP monitoring that could reduce measurement procedure from laborious inflation and deflation of cuff sensor. Compared to PTT-based methods for cuffless BP estimation [2], [7], [17], this study relies on a single-channel physiological measurement without bulky system and measurement preparation. Most of all, the proposed device provided two significant cardiovascular monitoring functions (BP and HR) using a single sensor.…”

“…The number of recruited subjects was comparable with most works to prove the concept for cardiovascular monitoring. Based on Table 1, most studies utilized PTT-based method for cuffless BP estimation [2], [7], [17], [18], [21]. Despite these technologies present the high reliable BP performance, the PTT-based method required at least two sensors that could make them unfeasible for wearable applications.…”

“…For example, the PTT-based BP monitoring must rely on two-channel physiological signals acquisition such as a combination of ECG and PPG devices [5] or double PPG sensors [6]. Fatemehsadat Tabei et al [7] utilized two-channel PPG signal measurements from the subject's index fingers to calculate PTT for BP estimation. However, the multi-devices that could cause device complexity and inconvenience in wearable applications.…”

Continuous Non-Invasive Blood Pressure Monitoring: A Methodological Review on Measurement Techniques

“…With attached electrodes and LED/photo detector sensors on a subject, the BP compared to the reference sphygmomanometer had a mean and standard deviation of -0.34±3.1 mmHg [22]. This method demonstrates PTT from ECG and PPG as an easier method of measuring for the comfort of patients and portability for continuous, long term monitoring; [84] an optical technique that measures the change of blood volume by photoelectric technique as well as measures the oxygen saturation in the blood Transmission Mode: earlobe, fingertip, toe Reflectance Mode: forehead, forearm, supraorbital artery, under the legs, and the wrist [46] slope transit time [81], arterial PTT [82], blocking-free opticaloscillometry [83], arteriolar PTT [84] inexpensive, simple set up external light and cold temperatures can add noise to data Speckle plethysmography (SPG) [52]- [55] an optical technique using laser speckle contrast imaging (LSCI) to monitor changes in blood flow finger [52], [53], wrist [54], [55] Laser Speckle Contrast Imaging [52]- [55] higher SNR compared to PPG in situations with more motion and cold climates, wearable sensors [52], [53] External Light can affect data and add noise [52], [53] Mechanicalbased [56]- [62] measuring the ejection of blood into the aorta and its transmission throughout the arterial system and it is expanded in response to the blood volume change through vessel; mechanical-based BP measurements include capacitive, ferroelectric, or piezoresistivesensors carotid artery, brachial artery, radial artery PTT [61], [62] [66], [85] an electrical impedance based noninvasive medical diagnostic procedure which measures small changes in the blood volume in terms of its electrical bioimpedance of a body part finger [44], [85], wrist [66] PTT (with Proximal or Distal Signals) [44], [66], ...…”