Blood Pressure Measurement Methods Research Articles

UWB-enabled Sensing for Fast and Effortless Blood Pressure Monitoring

Blood Pressure (BP) is a critical vital sign to assess cardiovascular health. However, existing cuff-based and wearable-based BP measurement methods require direct contact between the user's skin and the device, resulting in poor user experience and limited engagement for regular daily monitoring of BP. In this paper, we propose a contactless approach using Ultra-WideBand (UWB) signals for regular daily BP monitoring. To remove components of the received signals that are not related to the pulse waves, we propose two methods that utilize peak detection and principal component analysis to identify aliased and deformed parts. Furthermore, to extract BP-related features and improve the accuracy of BP prediction, particularly for hypertensive users, we construct a deep learning model that extracts features of pulse waves at different scales and identifies the different effects of features on BP. We build the corresponding BP monitoring system named RF-BP and conduct extensive experiments on both a public dataset and a self-built dataset. The experimental results show that RF-BP can accurately predict the BP of users and provide alerts for users with hypertension. Over the self-built dataset, the mean absolute error (MAE) and standard deviation (SD) for SBP are 6.5 mmHg and 6.1 mmHg, and the MAE and SD for DBP are 4.7 mmHg and 4.9 mmHg.

Validation of the RBP-9801 oscillometric blood pressure monitor in the general population according to the association for the Advancement of Medical Instrumentation/European Society of Hypertension/ International Organization for Standardization Universal Standard.

The aim of this study was to evaluate the accuracy of the single upper-arm cuff oscillometric blood pressure (BP) monitor RBP-9801 developed for office and home BP measurement in the general population according to the Association for the Advancement of Medical Instrumentation/European Society of Hypertension/International Organization for Standardization (AAMI/ESH/ISO) Universal Standard (ISO 81060-2:2018). Subjects were recruited to fulfil the age, gender, BP and cuff distribution criteria of the AAMI/ESH/ISO Universal Standard in general population using the same arm sequential BP measurement method. A total of 105 subjects were recruited and 85 were analyzed. For validation criterion 1, the mean±SD of the differences between the test device and reference BP readings was 2.3±6.4/3.1±5.8mmHg (systolic/diastolic). For criterion 2, the SD of the mean BP differences between the test device and reference BP per subject was 5.24/5.03mmHg (systolic/diastolic). The conclusion is that the RBP-9801 oscillometric device for office and home BP measurement fulfilled all the requirements of the AAMI/ESH/ISO Universal Standard (ISO 81060-2:2018) in the general population and can be recommended for clinic and self-use at home.

Determinants of prolonged baseline blood pressure restoration following autonomic dysreflexia for individuals with spinal cord injuries

Objective This study aimed to identify the determinants affecting the time required for blood pressure (BP) restoration after autonomic dysreflexia (AD) and to propose a new method for BP measurement in individuals with cervical spinal cord injury (SCI) who experience AD. Methods In a prospective, single-center observational study, participants’ bladders were filled with body-temperature saline until reaching cystometric capacity, as confirmed by previous urodynamic studies. Restoration time (RT), defined as the time from the onset of voiding until BP returned to baseline, was measured during the morning voiding session. This session involved the use of a 10F hydrophilic transurethral catheter. Data were then compared with various clinical determinants including demographic, urodynamic, and cystographic variables. Results The study included 29 individuals with cervical SCI. Notable variations in RT were observed among individuals with differing levels of detrusor overactivity (DO) and bladder compliance. An inverse correlation was noted between RT and bladder compliance, whereas positive correlations were identified with maximal detrusor pressure, peak systolic BP (SBP), and the magnitude of BP changes. Factors associated with prolonged RT included injury completeness, bladder trabeculation, vesicoureteral reflux (VUR), DO, and changes in SBP. Conclusions A significant association was found between BP elevation and prolonged RT. Determinants such as the severity of the SCI, bladder trabeculation, VUR, and DO were correlated with prolonged RT, considering their importance in the assessment of baseline BP following AD.

From video to vital signs: using personal device cameras to measure pulse rate and predict blood pressure using explainable AI

In this study, we address the need for low-cost, rapid, and reliable methods for blood pressure measurement to facilitate timely diagnosis and treatment of hypertension. We aim to enhance understanding and trust in the novel remote photoplethysmography technology, specifically as deployed by Lifelight®\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circledR$$\\end{document}, for vital sign monitoring. Lifelight®\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circledR$$\\end{document} utilizes remote photoplethysmography to extract physiologically meaningful features from video recordings on personal devices. This study describes the accurate calculation of pulse rates and the extraction of morphological and time series features from the remote photoplethysmography signal for blood pressure prediction. Unlike common approaches, distinct model types are employed for predicting systolic and diastolic blood pressure. Evaluation on an independent clinical laboratory’s dataset demonstrates the efficacy of the proposed method. The pulse rate accuracy, measured as root mean square error, is 1.9 beats per minute. The model for systolic blood pressure prediction shows a mean error of 1.2 mmHg and a standard deviation of 15.9 mmHg. The model for diastolic prediction shows a mean error of -\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-$$\\end{document}3.2 mmHg and a standard deviation of 13.1 mmHg. This research establishes the validity of remote photoplethysmography technology by showcasing accurate pulse rate calculations and effective feature extraction for blood pressure prediction. The results indicate the potential for widespread adoption of remote photoplethysmography in measuring blood pressure and other vital signs.

ACNN-BiLSTM: A Deep Learning Approach for Continuous Noninvasive Blood Pressure Measurement Using Multi-Wavelength PPG Fusion.

As an essential physiological indicator within the human body, noninvasive continuous blood pressure (BP) measurement is critical in the prevention and treatment of cardiovascular disease. However, traditional methods of blood pressure prediction using a single-wavelength Photoplethysmographic (PPG) have bottlenecks in further improving BP prediction accuracy, which limits their development in clinical application and dissemination. To this end, this study proposed a method to fuse a four-wavelength PPG and a BP prediction model based on the attention mechanism of a convolutional neural network and bidirectional long- and short-term memory (ACNN-BiLSTM). The effectiveness of a multi-wavelength PPG fusion method for blood pressure prediction was evaluated by processing PPG signals from 162 volunteers. The study compared the performance of the PPG signals with different individual wavelengths and using a multi-wavelength PPG fusion method in blood pressure prediction, assessed using mean absolute error (MAE), root mean squared error (RMSE) and AAMI-related criteria. The experimental results showed that the ACNN-BiLSTM model achieved a better MAE ± RMSE for a systolic BP and diastolic BP of 1.67 ± 5.28 and 1.15 ± 2.53 mmHg, respectively, when using the multi-wavelength PPG fusion method. As a result, the ACNN-BiLSTM blood pressure model based on multi-wavelength PPG fusion could be considered a promising method for noninvasive continuous BP measurement.

Validation of the Mindray VS9 Vital Signs Monitor in a combined adult and pediatric population according to ISO Standard 81060-2:2018.

We aimed to validate the accuracy of the Mindray VS9 Vital Signs Monitor, which features the Mindray TrueBP inflation algorithm for oscillometric blood pressure (BP) measurement, to check if it complies with the International Organization for Standardization Standard (ISO 81060-2:2018) in a combined adult and pediatric population. A total of 86 participants, including both adult and pediatric subjects, were recruited. The distribution of their ages, gender, BPs and limb sizes all complied with the requirement of the ISO standard. The inflation and deflation algorithms were validated independently using the same-arm sequential BP measurement method. For each subject, the BP was first determined by two independent observers using a mercury sphygmomanometer (R1). The BP of the subject was then determined by the third observer using the test equipment (T1). Then, using a mercury sphygmomanometer, two independent observers were asked to determine the subject's BP (R2) again. R1-T1-R2 were considered a valid pair of data. This cycle continued until 3 pairs of valid data were achieved. We collected 258 pairs of valid BP data for the validation of the inflation and deflation algorithms respectively. For validation Criterion 1, the mean ± SD of the differences between the readings obtained from the test device and reference BP was 0.0 ± 6.6/-1.8 ± 7.1 mmHg (systolic/diastolic) when the deflation algorithm was used, and 2.4 ± 6.3/ 0.3 ± 6.9 mmHg (systolic/diastolic) when the inflation algorithm was used. For validation Criterion 2, the SD of the averaged BP differences between the test device and the reference BP per subject was 5.35/6.33 mmHg (systolic/diastolic) when the deflation algorithm was used, and 5.17/5.75 mmHg (systolic/diastolic) when the inflation algorithm was used. The VS9 Vital Signs Monitor fulfilled all the criteria in the ISO Standard. Moreover, the inflation algorithm had a shorter Measure Time (by 7-21 s) and lower maximum inflation pressure (by 9.7-22 mmHg). The VS9 Vital Signs Monitor fulfilled all the requirements of the ISO Standard (ISO 81060-2:2018) in a combined adult and pediatric population and is recommended for clinical use.

UbiHeart: A novel approach for non-invasive blood pressure monitoring through real-time facial video

Monitoring blood pressure (BP) is an essential component of evaluating cardiovascular health, aiding in the early detection and management of hypertension-related complications. Traditional methods of BP measurement often involve invasive or cumbersome devices, leading to discomfort and reduced compliance. We propose a framework to monitor BP non-invasively, analyzing the face video captured by a webcam or smartphone camera leveraging the relationship of image-based Pulse Transit Time (iPTT) and Heart Rate Variability (HRV) with BP. We have built a dataset of 90 sets of collected videos using a mobile phone front camera and BP data from a standard digital BP monitor from 12 individuals from an approved Institutional Review Board (IRB) to evaluate our system. We have got a Mean Absolute Error (MAE) of 10.35+/−2.5 mmHg for systolic BP (SBP) and 7.8+/−1.5 mmHg for diastolic BP (DBP) while using the HRV representation RMSSD. On the other hand, an MAE of 8.25+/−3.5 mmHg for SBP and 7.7+/−2.5 mmHg for DBP while using the HRV representation SDRR. Finally, we have developed a framework and built a real-time system to monitor BP as a mobile and web-based application that can facilitate early detection of trends and anomalies, allowing healthcare providers to intervene promptly and personalize treatment plans.

Evaluation of the oscillometric method for noninvasive blood pressure measurement during cuff deflation and cuff inflation with reference to intra-arterial blood pressure.

There is little quantitative clinical data available to support blood pressure measurement accuracy during cuff inflation. In this study of 35 male and 5 female lightly anaesthetized subjects aged 64.1 ± 9.6 years, we evaluate and compare the performance of both the oscillometric ratio and gradient methods during cuff deflation and cuff inflation with reference to intra-arterial measurements. We show that the oscillometric waveform envelopes (OWE), which are key to both methods, exhibit significant variability in both shape and smoothness leading to at least 15% error in the determination of mean pressure (MP). We confirm the observation from our previous studies that K1 Korotkoff sounds underestimate systolic blood pressure (SBP) and note that this underestimation is increased during cuff inflation. The estimation of diastolic blood pressure (DBP) is generally accurate for both the ratio and the gradient method, with the latter showing a significant increase during inflation. Since the gradient method estimates SBP and DBP from points of maximum gradient on each OWE recorded, it may offer significant benefits over the ratio method. However, we have shown that the ratio method can be optimized for any data set to achieve either a minimum mean error (ME) of close to 0 mmHg or minimum root mean square error (RMSE) with standard deviation (SD) of <5.0 mmHg. We conclude that whilst cuff inflation may offer some advantages, these are neither significant nor substantial, leaving as the only benefit, the potential for more rapid measurement and less patient discomfort.

Validation of the Raycome model M2 ambulatory blood pressure monitor in the general population according to the Association for the Advancement of Medical Instrumentation/European Society of Hypertension/International Organization for Standardization Universal Standard (ISO 81060-2:2018).

The aim of this study was to evaluate the accuracy of the Raycome model M2 oscillometric upper-arm blood pressure (BP) monitor developed for ambulatory BP measurement in the general population according to the Association for the Advancement of Medical Instrumentation/European Society of Hypertension/International Organization for Standardization (AAMI/ESH/ISO) Universal Standard (ISO 81060-2:2018) at rest and during dynamic exercise. Subjects were recruited to fulfill the age, gender, BP and cuff distribution criteria of the AAMI/ESH/ISO Universal Standard in the general population using the same arm sequential BP measurement method. Three cuffs of the test device were used for arm circumference 18-22 cm (small), 22-32 cm (medium) and 32-42 cm (large). For the general validation study, 106 subjects were recruited and 85 were analyzed. For validation criterion 1, the mean ± SD of the differences between the test device and reference BP readings was 0.5 ± 6.2/-0.2 ± 5.1 mmHg (systolic/diastolic). For criterion 2, the SD of the mean BP differences between the test device and reference BP per subject was 5.23/4.50 mmHg (systolic/diastolic). In the ambulatory validation study ( N = 35), the mean difference was 0.4 ± 5.9/-1.1 ± 5.8 mmHg. The Raycome model M2 performed well against the standard in both the general and ambulatory validations and the Bland-Altman plots did not show any systematic variation in the error. These data show that the Raycome model M2 monitor meets the requirements of the AAMI/ESH/ISO Universal Standard (ISO 81060-2:2018) and in the ambulatory setting, indicating its suitability for measuring BP in the general population.

A multi-channel photoplethysmography array with contact-force regulation for tonoarteriographic imaging

Aim: Photoplethysmography (PPG) has gained widespread popularity as a non-invasive method for potential cuff-less blood pressure (BP) measurement in smart devices. However, the accuracy of PPG-based devices is often hindered by motion artifacts, site variability, and inconsistent contact force (CF). This study aims to investigate the influence of CF variations on PPG signals. Methods: To address these challenges, we present a novel approach involving a multi-channel PPG array integrated with CF regulation in the form of a wearable wristband. This platform enables the visualization of regional PPG/BP distribution while simultaneously monitoring CF. Moreover, our research explored the relationship between PPG waveform characteristics and CF during wrist extension. Results: The results of this study reveal that the PPG amplitude (PPGA) and the b/a ratios, computed from the second derivative peaks of the PPG AC pulse wave, exhibit inconsistency in reaction to CF variations. Notably, a shape correlation coefficient of 0.65069 between normalized PPG and flipped CF sheds light on how changes in posture affect PPG measurements. Conclusions: The proposed platform shows promise in mitigating the effects of CF and spatial positioning on PPG, thereby improving measurement precision and offering a novel approach to image tonoarteriographic (TAG) activities for continuous hypertension management.

Single-Cycle Pulse Signal Recognition Based on One-Dimensional Deep Convolutional Neural Network

Pulse signals carry comprehensive information regarding human cardiovascular physiology and pathology, providing a noninvasive and continuous method to assess cardiovascular health status in blood pressure monitoring. The blood pressure measurement method based on the pulse signal needs to extract the features of the single-cycle pulse signal, while the pulse signal pertains to the weak physiological signal of body surface. The acquisition process is susceptible to various factors leading to abnormal cycles, especially adjacent channel interference, affecting the subsequent feature extraction. To address this problem, this paper conducts an analysis of the formation mechanism of adjacent channel interference and proposes a single-cycle pulse signal recognition algorithm based on a one-dimensional deep convolutional neural network (1D-CNN) model. Radial pulse signals were collected from 150 subjects by pulse bracelet, and a dataset comprising 3446 single-cycle signals was extracted in total after denoising, single-cycle segmentation, and standardized preprocessing. The 1D-CNN model is trained to classify input signals into three categories: effective pulse signals, distortion, and interference signals. This classification is achieved by evaluating the waveform morphology of the signals within a single cycle. The results show that the overall classification accuracy of the algorithm on the test set is 98.26%, in which the classification accuracy of pulse waves is 99.8%, indicating that it can effectively recognize single-cycle pulse waves, which lays the foundation for subsequent continuous blood pressure measurement.

Phytochemical and pharmacological evaluation of the anti-hypertensive effect of Theobroma Cacao

Background: This study evaluated the effects of chloroform and ethanol extracts of Theobroma Cacao (T.Cacao) in nitro-L-arginine, methyl esters (L-NAME)-induced hypertensive rats. The acute toxicity and phytochemical analyses of the extracts were carried out using standard methods while hemodynamic parameters of hypertensive rats treated with the extracts were assayed using invasive and non-invasive methods of blood pressure measurements. The percentage yield of the extract was 3.25% (ethanol) and 15.77% (chloroform). The phytochemical analyses revealed the presence of flavonoids, alkaloids, steroids, saponins, anthraquinone, tannins and, cardiac glycosides. Concurrent administration of the extracts with L-NAME showed a significant (p&lt;0.05) decrease in systolic blood pressure, diastolic blood pressure, pulse pressure, and mean arterial pressure in the treated rats compared with the untreated rats. The mechanism of action showed that ethanol extract led to significant (p&lt;0.05) decreases in systolic blood pressure, diastolic blood pressure, pulse pressure and mean arterial pressure also in the presence of muscarinic antagonist (atropine). The isolated rat thoracic aorta showed a slight decrease at each concentration but not statistically significant (p&lt;0.05), it was statistically significant at 50mg/ml while in the presence of high KCl, there were significant (p&lt;0.05) decreases at each of the concentrations compared with the control. The observed results showed that consumption of T. cacao within the experimental dose prevented an increase in hemodynamic status of Wistar rats. Thus, if these results are extrapolated to man, consumption of T. cacao should be encouraged.

Accurate detection of Korotkoff sounds reveals large discrepancy between intra-arterial systolic pressure and simultaneous noninvasive measurement of blood pressure with brachial cuff sphygmomanometry.

Cardiovascular disease is the number 1 cause of death globally, with elevated blood pressure (BP) being the single largest risk factor. Hence, BP is an important physiological parameter used as an indicator of cardiovascular health. Noninvasive cuff-based automated monitoring is now the dominant method for BP measurement and irrespective of whether the oscillometric or the auscultatory method is used, all are calibrated according to the Universal Standard (ISO 81060-2:2019), which requires two trained operators to listen to Korotkoff K1 sounds for SBP and K4/K5 sounds for DBP. Hence, Korotkoff sounds are fundamental to the calibration of all NIBP devices. In this study of 40 lightly sedated patients, aged 64.1 ± 9.6 years, we compare SBP and DBP recorded directly by intra-arterial fluid filled catheters to values recorded from the onset (SBP-K) and cessation (DBP-K) of Korotkoff sounds. We demonstrate that whilst DBP-K measurements are in good agreement, with a mean difference of -0.3 ± 5.2 mmHg, SBP-K underestimates true intra-arterial SBP (IA-SBP) by an average of 14 ± 9.6 mmHg. The underestimation arises from delays in the re-opening of the brachial artery following deflation of the brachial cuff to below SBP. The reasons for this delay are not known but appear related to the difference between SBP and the pressure under the cuff as blood first begins to flow, as the cuff deflates. Linear models are presented that can correct the underestimation in SBP resulting in estimates with a mean difference of 0.2 ± 7.1 mmHg with respect to intra-arterial SBP.

Screening for hypertension in adults: protocol for evidence reviews to inform a Canadian Task Force on Preventive Health Care guideline update

PurposeTo inform updated recommendations by the Canadian Task Force on Preventive Health Care on screening in a primary care setting for hypertension in adults aged 18 years and older. This protocol outlines the scope and methods for a series of systematic reviews and one overview of reviews.MethodsTo evaluate the benefits and harms of screening for hypertension, the Task Force will rely on the relevant key questions from the 2021 United States Preventive Services Task Force systematic review. In addition, a series of reviews will be conducted to identify, appraise, and synthesize the evidence on (1) the association of blood pressure measurement methods and future cardiovascular (CVD)-related outcomes, (2) thresholds for discussions of treatment initiation, and (3) patient acceptability of hypertension screening methods. For the review of blood pressure measurement methods and future CVD-related outcomes, we will perform a de novo review and search MEDLINE, Embase, CENTRAL, and APA PsycInfo for randomized controlled trials, prospective or retrospective cohort studies, nested case–control studies, and within-arm analyses of intervention studies. For the thresholds for discussions of treatment initiation review, we will perform an overview of reviews and update results from a relevant 2019 UK NICE review. We will search MEDLINE, Embase, APA PsycInfo, and Epistemonikos for systematic reviews. For the acceptability review, we will perform a de novo systematic review and search MEDLINE, Embase, and APA PsycInfo for randomized controlled trials, controlled clinical trials, and observational studies with comparison groups. Websites of relevant organizations, gray literature sources, and the reference lists of included studies and reviews will be hand-searched. Title and abstract screening will be completed by two independent reviewers. Full-text screening, data extraction, risk-of-bias assessment, and GRADE (Grading of Recommendations Assessment, Development and Evaluation) will be completed independently by two reviewers. Results from included studies will be synthesized narratively and pooled via meta-analysis when appropriate. The GRADE approach will be used to assess the certainty of evidence for outcomes.DiscussionThe results of the evidence reviews will be used to inform Canadian recommendations on screening for hypertension in adults aged 18 years and older.Systematic review registrationThis protocol is registered on PROSPERO and is available on the Open Science Framework (osf.io/8w4tz).

Blood pressure measurements for diagnosing hypertension in primary care: room for improvement

BackgroundIn the adult population, about 50% have hypertension, a risk factor for cardiovascular disease and subsequent premature death. Little is known about the quality of the methods used to diagnose hypertension in primary care.ObjectivesThe objective was to assess the frequency of use of recognized methods to establish a diagnosis of hypertension, and specifically for OBPM, whether three distinct measurements were taken, and how correctly the blood pressure levels were interpreted.MethodsA retrospective population-based cohort study using electronic medical records of patients aged between 40 and 70 years, who visited their general practitioner (GP) with a new-onset of hypertension in the years 2012, 2016, 2019, and 2020. A visual chart review of the electronic medical records was used to assess the methods employed to diagnose hypertension in a random sample of 500 patients. The blood pressure measurement method was considered complete if three or more valid office blood pressure measurements (OBPM) were performed, or home-based blood pressure measurements (HBPM), the office- based 30-minute method (OBP30), or 24-hour ambulatory blood pressure measurements (24 H-ABPM) were used.ResultsIn all study years, OBPM was the most frequently used method to diagnose new-onset hypertension in patients. The OBP-30 method was used in 0.4% (2012), 4.2% (2016), 10.6% (2019), and 9.8% (2020) of patients respectively, 24 H-ABPM in 16.0%, 22.2%, 17.2%, and 19.0% of patients and HBPM measurements in 5.4%, 8.4%, 7.6%, and 7.8% of patients, respectively. A diagnosis of hypertension based on only one or two office measurements occurred in 85.2% (2012), 87.9% (2016), 94.4% (2019), and 96.8% (2020) of all patients with OBPM. In cases of incomplete measurement and incorrect interpretation, medication was still started in 64% of cases in 2012, 56% (2016), 60% (2019), and 73% (2020).ConclusionOBPM is still the most often used method to diagnose hypertension in primary care. The diagnosis was often incomplete or misinterpreted using incorrect cut-off levels. A small improvement occurred between 2012 and 2016 but no further progress was seen in 2019 or 2020. If hypertension is inappropriately diagnosed, it may result in under treatment or in prolonged, unnecessary treatment of patients. There is room for improvement in the general practice setting.

Elderly patient with syncope: the clinical case

Recurrent syncope in the elderly is of particular concern to the clinician. Differential diagnosis of syncope in such patients presents significant difficulties due to high comorbidity. For patients over 70 years old, an increased number of syncopal episodes is typical; syncope becomes one of the leading reasons for their emergency hospitalization. The importance of determining the exact cause of syncope in this case cannot be overestimated: frequent falls significantly reduce the quality of life and can lead to serious injuries or even be fatal. Therefore, today it is critically important to have modern diagnostic methods that can help determine the etiology of syncope. The presented clinical case demonstrates a diagnostic search using continuous non-invasive “beat-to-beat” blood pressure measurement methods during such provocative tests as a passive orthostatic test and a carotid sinus massage. This technique is used routinely in the USA and European countries but is not enough widespread in the Russian Federation. Such a tool may simplify the differential diagnosis of syncope.

Non-Invasive Blood Pressure Tracking of Spontaneous Hypertension Rats Using an Electronic Nose.

Traditional noninvasive blood pressure measurement methods in experimental animals are time consuming and difficult to operate, particularly for large numbers of animals. In this study, the possibility of sensing fecal odor to estimate the blood pressure status of spontaneous hypertension rats (SHRs) was explored with the aim of establishing a new method for non-invasive monitoring of blood pressure. The body weight and blood pressure of SHRs kept increasing with growth, and the odor information monitored using an E-nose varied with the blood pressure status, particularly for sensors S6 and S7. The fecal information was analyzed using principal component analysis, canonical discriminant analysis and multilayer perception neural networks (MLP) to discriminate SHRs from normal ones, with a 100% correct classification rate. For better prediction of blood pressure, the model built using multiple linear regression analysis, partial least squares regression analysis and multilayer perceptron neural network analysis were used, with coefficients of determination (R2) ranging from 0.8036 to 0.9926. Moreover, the best prediction model for blood pressure was established using MLP analysis with an R2&not; higher than 0.91. Thus, changes in blood pressure levels can be tracked non-invasively, and normotension can be distinguished from hypertension or even at different hypertension levels based on the odor information of rat feces, providing a foundation for non-invasive health monitoring. This work might provide potential instructions for functional food research aimed at lowering blood pressure.

Cuff‐less blood pressure estimation using hetero‐core optical fibers

AbstractIn this study, we proposed a cuff‐less blood pressure measurement using a medical tape sensor with an embedded hetero‐core optical fiber. The tape sensor pasted on the skin can directly detect pulse wave signals with a simple measuring device. Pulse transit time (PTT) was obtained from the time difference between the two pulse waveforms at the neck and foot. Systolic blood pressure (SBP) was estimated from PTT and the regression equation. The result shows that the maximum prediction error was 3.8 mmHg in five healthy young subjects. The SBP data were evaluated using a Bland‐Altman method to assess the agreement of SBP data estimated by the proposed method with those measured by the cuff‐based electronic sphygmomanometer. The mean ± 1.96 standard deviation of the estimated SBP against the reference was −1.3 ± 5.1 mmHg. The results show that the proposed noninvasive blood pressure measurement method can measure blood pressure, and its accuracy is comparable to that of the cuff‐based electronic sphygmomanometer.

History of blood pressure measurement in newborns and infants.

The development of methods for measuring blood pressure (BP) in newborns and small children has a rich history. Methods for BP measuring in adults had to be adapted to this age group. For measuring BP in direct invasive way, a suitable approach had to be found to access the arterial circulation through the umbilical and later radialis artery. Currently, results obtained from direct invasive BP measurement are considered the "gold standard". The development of non-invasive methods for BP measuring in newborns and children began with the use of von Basch's sphygmomanometer (1880). In 1899, Gustav Gärtner constructed the device, which was the basis for the flush method. After the discovery of the palpation and auscultation methods, these methods were also used for BP measurement in newborns and children, however, the BP values obtained in these ways were typically underestimated using excessively wide cuffs. From the auscultation method, methods utilizing ultrasound and infrasound to detect arterial wall movement and blood flow were later developed. The oscillometric method for BP measurement was introduced by E. J. Marey so early as in 1876. In 1912, P. Balard used the oscillometric technique to measure blood pressure in a large group of newborns. Through different types of oscillometers using various methods for detecting vascular oscillations (such as xylol method, impedance and volume plethysmography, etc.), the development has continued to assessment of vascular oscillations by modern sensor technology and software. For continuous non-invasive blood pressure measurement, the volume-clamp method, first described by Jan Peňáz in 1968, was developed. After modification for use in newborns, application of the cuff to the wrist instead of the finger, it is primarily used in clinical physiological studies to evaluate beat-to-beat BP and heart rate pressure variability, such as in the determination of the baroreflex sensitivity.

A Novel Convolutional Neural Network Deep Learning Implementation for Cuffless Heart Rate and Blood Pressure Estimation

Cardiovascular diseases (CVDs) affect components of the circulatory system responsible for transporting blood through blood vessels. The measurement of the mechanical force acting on the walls of blood vessels, as well as the blood flow between heartbeats and when the heart is at rest, is known as blood pressure (BP). Regular assessment of BP can aid in the prevention and early detection of CVDs. In the present research, a deep learning algorithm was developed to accurately calculate both blood pressure (BP) and heart rate (HR) by extracting relevant features from photoplethysmogram (PPG), electrocardiogram (ECG), and ABP signals. This algorithm was implemented using the Medical Information Mart for Intensive Care (MIMIC-II) dataset. It captures vital blood pressure-related features extracted from the PPG signal and accounts for the time relationship with the ECG. The algorithm also determines the values of systolic blood pressure (SBP) and diastolic blood pressure (DBP) based on the ABP waveform through a convolutional neural network and stepwise multivariate linear regression. In comparison with other established BP measurement methods, our proposed approach achieved better results, with a mean absolute error (MAE) of approximately 4.7 mmHg for SBP and 2.1 mmHg for DBP, respectively. The standard deviation (STD) for SBP and DBP was approximately 7.6 mmHg and 3.9 mmHg, respectively. This study makes a valuable contribution to the healthcare field by introducing a novel, cost-effective continuous BP measurement method with improved accuracy while also minimizing the data dimension without losing any important information.