Wearable Blood Pressure Monitoring Device Research Articles

Wearable Continuous Blood Pressure Monitoring Devices Based on Pulse Wave Transit Time and Pulse Arrival Time: A Review.

Continuous blood pressure (BP) monitoring is of great significance for the real-time monitoring and early prevention of cardiovascular diseases. Recently, wearable BP monitoring devices have made great progress in the development of daily BP monitoring because they adapt to long-term and high-comfort wear requirements. However, the research and development of wearable continuous BP monitoring devices still face great challenges such as obvious motion noise and slow dynamic response speeds. The pulse wave transit time method which is combined with photoplethysmography (PPG) waves and electrocardiogram (ECG) waves for continuous BP monitoring has received wide attention due to its advantages in terms of excellent dynamic response characteristics and high accuracy. Here, we review the recent state-of-art wearable continuous BP monitoring devices and related technology based on the pulse wave transit time; their measuring principles, design methods, preparation processes, and properties are analyzed in detail. In addition, the potential development directions and challenges of wearable continuous BP monitoring devices based on the pulse wave transit time method are discussed.

PS-C07-7: EFFECTS OF PSYCHOLOGICAL STRESS AND PHYSICAL ACTIVITY ON AMBULATORY BLOOD PRESSURE AND PULSE RATE VARIABILITY

Objectives: Physical activity and psychological stress during daily life contribute to ambulatory blood pressure (BP) variability. This study aims to investigate the effects of physical activity and psychological stress on daytime BPs measured by ABPM. Methods: This study is a post-hoc analysis using ABPM data from a comparison study of ambulatory BP measured by a wrist watch-type wearable BP monitoring device and an ABPM device. ABPM was performed at 30-min intervals for 24 h using a TM-2441 device (A&D Co., Tokyo), an oscillometric device with an upper-arm BP-cuff. This device is also equipped with a high-sensitivity actigraph that can detect fine-scale physical movements of the wearer in three directions. Physical activity was calculated as the sum of the actigraphically measured physical activity over the 5 min before each ABPM measurement. Study participants were asked to write a self-report diary of their general situation (i.e., location, emotion, and body position) corresponding to each BP measurement at least 10 times while awake. Results: From 50 outpatients (mean age 66.1 ± 10.8 years, 60.0% male, 98.0% hypertensive patients), 1580 daytime BP readings were taken by ABPM. Of these, 642 BP readings had corresponding diary information. In the mixed effect model analysis including physical activity, significant systolic BP (SBP) elevation associated with physical activity was observed in both a dataset of 1580 BP readings (2.9 ± 0.9 mmHg, P = 0.001 for light physical activity; and 2.9 ± 1.4 mmHg, P = 0.045 for moderate physical activity) and a dataset of 642 BP readings (2.5 ± 1.2 mmHg, P = 0.043 for light physical activity; and 4.2 ± 2.0 mmHg, P = 0.036 for moderate physical activity). In the analysis of 642 BP readings using the model including physical activity and situational factors from diary information, SBP was significantly higher during negative emotions than during positive emotions (7.4 ± 2.5 mmHg, p = 0.003), while the SBP change to physical activity decreased and was not statistically significant. On the other hand, pulse rate was unchanged by negative emotions, but was increased for physical activity. Conclusions: Daytime BP measured by ABPM was elevated to a greater extent by psychological stress than by physical activity. BP elevation without corresponding pulse rate increase might be influenced by psychological stress. Simultaneous monitoring of BP and physical activity might detect BP elevation caused by psychological stress.

Wearable blood pressure measurement devices and new approaches in hypertension management: the digital era.

Out-of-office blood pressure (BP) measurement is considered an integral component of the diagnostic algorithm and management of hypertension. In the era of digitalization, a great deal of wearable BP measuring devices has been developed. These digital blood pressure monitors allow frequent BP measurements with minimal annoyance to the patient while they do promise radical changes regarding the diagnostic accuracy, as the importance of making an accurate diagnosis of hypertension has become evident. By increasing the number of BP measurements in different conditions, these monitors allow accurate identification of different clinical phenotypes, such as masked hypertension and pathological BP variability, that seem to have a negative impact on cardiovascular prognosis. Frequent measurements of BP and the incorporation of new features in BP variability, both enable well-rounded interpretation of BP data in the context of real-life settings. This article is a review of all different technologies and wearable BP monitoring devices.

Relationship between blood pressure repeatedly measured by a wrist-cuff oscillometric wearable blood pressure monitoring device and left ventricular mass index in working hypertensive patients.

This study sought to evaluate the relationship between blood pressure (BP) taken by a new wrist-cuff oscillometric wearable BP monitoring device and left ventricular mass index measured by cardiac magnetic resonance imaging (cMRI-LVMI) in 50 hypertensive patients (mean age 60.5 ± 8.9 years, 92.0% men, 96% treated for hypertension) with regular employment. Participants were asked to self-measure their wearable BPs twice in the morning and evening under a guideline-recommended standardized home BP measurement, and once each at five predetermined times and any additional time points under an ambulatory condition for a maximum of 7 days. In total, 2105 wearable BP measurements (home BP: 747 [morning: 409, evening: 338], ambulatory condition: 1358 [worksite: 942]) were collected over 5.5 ± 1.2 days. The average of all wearable systolic BP (SBP) readings (129.8 ± 11.0 mmHg) was weakly correlated with cMRI-LVMI (r = 0.265, p = 0.063). Morning home wearable SBP average (128.5 ± 13.8 mmHg) was significantly correlated with cMRI-LVMI (r = 0.378, p = 0.013), but ambulatory wearable SBP average (132.5 ± 12.7 mmHg) was not (r = 0.215, p = 0.135). The averages of the highest three values of all wearable SBPs (153.3 ± 13.9 mmHg) and ambulatory wearable SBPs (152.9 ± 13.9 mmHg) were 16 mmHg higher than that of the morning home wearable SBPs (137.0 ± 15.9 mmHg). Those peak values were significantly correlated with cMRI-LVMI (r = 0.320, p = 0.023; r = 0.310, p = 0.029; r = 0.451, p = 0.002, respectively). In conclusion, an increased number of wearable BP measurements, which could detect individual peak BP, might add to the clinical value of these measurements as a complement to the guideline-recommended home BP measurements, but further studies are needed to confirm these findings.

Ambulatory Blood Pressure Monitoring to Diagnose and Manage Hypertension.

This review portrays how ambulatory blood pressure (BP) monitoring was established and recommended as the method of choice for the assessment of BP and for the rational use of antihypertensive drugs. To establish much-needed diagnostic ambulatory BP thresholds, initial statistical approaches evolved into longitudinal studies of patients and populations, which demonstrated that cardiovascular complications are more closely associated with 24-hour and nighttime BP than with office BP. Studies cross-classifying individuals based on ambulatory and office BP thresholds identified white-coat hypertension, an elevated office BP in the presence of ambulatory normotension as a low-risk condition, whereas its counterpart, masked hypertension, carries a hazard almost as high as ambulatory combined with office hypertension. What clinically matters most is the level of the 24-hour and the nighttime BP, while other BP indexes derived from 24-hour ambulatory BP recordings, on top of the 24-hour and nighttime BP level, add little to risk stratification or hypertension management. Ambulatory BP monitoring is cost-effective. Ambulatory and home BP monitoring are complimentary approaches. Their interchangeability provides great versatility in the clinical implementation of out-of-office BP measurement. We are still waiting for evidence from randomized clinical trials to prove that out-of-office BP monitoring is superior to office BP in adjusting antihypertensive drug treatment and in the prevention of cardiovascular complications. A starting research line, the development of a standardized validation protocol for wearable BP monitoring devices, might facilitate the clinical applicability of ambulatory BP monitoring.

Achieving Optimal Gestational Weight Gain, Birth Weight, and Perinatal Outcomes Among Pregnant Women at Risk of Hypertension: Protocol for a Pilot Randomized Controlled Trial.

BackgroundHypertensive disorders, including preeclampsia, complicate 10% of all pregnancies, causing maternal and fetal morbidity and mortality. In Bangladesh, 24% of all maternal deaths are directly attributed to hypertensive disorders. Conventional antenatal care practices often delay or miss detecting hypertensive disorders in pregnancy, which may allow some women to become vulnerable to the adverse consequences of the hypertensive disorders. Regular self-monitoring of blood pressure and weight gain may improve maternal and fetal outcomes among pregnant women at risk of developing hypertensive disorders during pregnancy through early diagnosis, prompt referral, and timely clinical management; however, to undertake a randomized controlled trial of an intervention to reduce adverse consequences of hypertensive disorders in pregnancy, its feasibility must first be determined.ObjectiveThe objectives of this study are to evaluate the accuracy of a wearable blood pressure monitoring device (Health Gauge) in order to test the design and methods of a future definitive randomized controlled trial, and to examine the feasibility, acceptability, and fidelity of an intervention focusing on regular monitoring of weight gain and self-monitoring of blood pressure for pregnant women at risk of developing hypertensive disorders and their associated complications.MethodsThe study is located in Matlab, Bangladesh will be conducted in two phases. First, a wearable blood pressure device (Health Gauge) will be validated in accordance with the European Society of Hypertension International Protocol (revision 2010). Second, a prospective, two-arm, parallel, and nonblinded randomized controlled external pilot trial will be conducted. In the pilot trial, 70 eligible participants will be individually randomized to the intervention arm, in which pregnant women will self-monitor their blood pressure daily using a wearable device (Health Gauge) and be evaluated monthly by trained health workers for weight gain from 20 weeks of gestation until delivery, or the control arm, in which pregnant women will be assessed for weight gain every two months from 20 weeks of gestation until delivery (1:1 intervention to control allocation ratio using a permuted block randomization method with concealment). All women will receive standard antenatal care.ResultsA validation study of the wearable blood pressure device has successfully been conducted among the general adult population in Matlab, Bangladesh. As of September 2019, the pilot trial has completed enrollment of women who are pregnant (N=70; intervention: n=35; control: n=35) and follow-up of the participants is ongoing. Data analysis is expected to be completed by June 2020, and results are expected to be submitted for publication in August 2020.ConclusionsThe findings of this study will help us to design a comprehensive, full-scale randomized controlled trial to test the efficacy of regular self-monitoring of blood pressure and weight gain during pregnancy, a simple and inexpensive intervention to help to achieve optimal maternal and fetal outcomes in pregnant women at risk of developing hypertensive disorders and their associated complications during pregnancy.Trial RegistrationClinicalTrials.gov NCT03858595; https://clinicaltrials.gov/ct2/show/NCT03858595International Registered Report Identifier (IRRID)DERR1-10.2196/16676

Validation and Acceptability of a Cuffless Wrist-Worn Wearable Blood Pressure Monitoring Device Among Users and Health Care Professionals: Mixed Methods Study.

BackgroundBlood pressure (BP) is an important modifiable cardiovascular risk factor, yet its long-term monitoring remains problematic. Wearable cuffless devices enable the capture of multiple BP measures during everyday activities and could improve BP monitoring, but little is known about their validity or acceptability.ObjectiveThis study aimed to validate a wrist-worn cuffless wearable BP device (Model T2; TMART Technologies Limited) and assess its acceptability among users and health care professionals.MethodsA mixed methods study was conducted to examine the validity and comparability of a wearable cuffless BP device against ambulatory and home devices. BP was measured simultaneously over 24 hours using wearable and ambulatory devices and over 7 days using wearable and home devices. Pearson correlation coefficients compared the degree of association between the measures, and limits of agreement (LOA; Bland-Altman plots) were generated to assess measurement bias. Semistructured interviews were conducted with users and 10 health care professionals to assess acceptability, facilitators, and barriers to using the wearable device. Interviews were audio recorded, transcribed, and analyzed.ResultsA total of 9090 BP measurements were collected from 20 healthy volunteers (mean 20.3 years, SD 5.4; N=10 females). Mean (SD) systolic BP (SBP)/diastolic BP (DBP) measured using the ambulatory (24 hours), home (7 days), and wearable (7 days) devices were 126 (SD 10)/75 (SD 6) mm Hg, 112 (SD 10)/71 (SD 9) mm Hg and 125 (SD 4)/77 (SD 3) mm Hg, respectively. Mean (LOA) biases and precision between the wearable and ambulatory devices over 24 hours were 0.5 (−10.1 to 11.1) mm Hg for SBP and 2.24 (−17.6 to 13.1) mm Hg for DBP. The mean biases (LOA) and precision between the wearable and home device over 7 days were −12.7 (−28.7 to 3.4) mm Hg for SBP and −5.6 (−20.5 to 9.2) mm Hg for DBP. The wearable BP device was well accepted by participants who found the device easy to wear and use. Both participants and health care providers agreed that the wearable cuffless devices were easy to use and that they could be used to improve BP monitoring.ConclusionsWearable BP measures compared well against a gold-standard ambulatory device, indicating potential for this user-friendly method to augment BP management, particularly by enabling long-term monitoring that could improve treatment titration and increase understanding of users’ BP response during daily activity and stressors.

Cuff-less and Calibration-free Blood Pressure Estimation Using Convolutional Autoencoder with Unsupervised Feature Extraction.

Monitoring blood pressure (BP) in people's daily life in an unobtrusive way is of great significance to prevent cardiovascular disease and its complications. However, most of the current cuff-less BP estimation methods still suffer from two drawbacks including calibration and tedious feature selection. In this study, we first attempt to validate the feasibility of convolutional autoencoder (CAE) to estimate continuous BP without calibration and hand-crafted feature extraction. 62 subjects were recruited in this experiment. We first trained the CAE on all the data to extract the unsupervised features. Then, we trained a regressor to estimate BP values using the features learning from the CAE. 10-fold cross-validation tests were used to examine the performance of our models. Finally, it has been demonstrated that the accuracy of the predicted BP satisfied the Grade B standard of British Hypertension Society. Due to its calibration-free and unsupervised feature learning ability from the collected signal, the proposed method has high prospects for application in wearable BP monitoring device.

Novel blood pressure estimation method using single photoplethysmography feature.

Continuous blood pressure (BP) monitoring has a significant meaning to the prevention and early diagnosis of cardiovascular disease. However, existing continuous BP monitoring approaches, especially cuff-less BP monitoring approaches, are all contraptions which complex and huge computation required. For example, for the most sophisticated cuff-less BP monitoring method using pulse transit time (PTT), the simultaneous record of photoplethysmography (PPG) signal and electrocardiography (ECG) are required, and various measurement of characteristic points are needed. These issues hindered widely application of cuff less BP measurement in the wearable devices. In this study, a novel BP estimation method using single PPG signal feature was proposed and its performance in BP estimation was also tested. The results showed that the new approach proposed in this study has a mean error -0.91 ± 3.84 mmHg for SBP estimation and -0.36 ± 3.36 mmHg for DBP estimation respectively. This approach performed better than the traditional PTT based BP estimation, which mean error for SBP estimation was -0.31 ± 4.78 mmHg, and for DBP estimation was -0.18 ± 4.32 mmHg. Further investigation revealed that this new BP estimation approach only required measurement of one characteristic point, reducing much computation when implementing. These results demonstrated that this new approach might be more suitable implemented in the wearable BP monitoring devices.