Blood Pressure Measurement System Research Articles

Development of Non-Invasive Continuous Blood Pressure Measurement System Based on Multiple Feature Parameters

To address the issue of the difficulty in implementing non-invasive continuous blood pressure measurement technology in China, this study developed a high-performance synchronous electrocardiogram (ECG) and photoplethysmography (PPG) signal acquisition system. A PC-based human-computer interaction software platform was constructed, and continuous blood pressure measurement-related algorithms were integrated. Multiple feature parameters such as pulse wave transit time based on synchronous ECG and PPG signals were extracted, enabling non-invasive continuous blood pressure measurement. To verify the measurement accuracy of the system, tests and comparative verifications were carried out. The results demonstrated that the system could meet the requirements of relevant standards and have good application value.

Correlation between antihypertensive drugs and cerebral hemodynamic parameters: insights from observational findings using transcranial Doppler.

Antihypertensives (AHD) can influence cerebral autoregulation (CA) and attenuate hypertrophic concentric remodelling of arterioles. The aim of this study was to examine the associations between AHD, CA and structural and functional properties of cerebral arteries. In this observational, cross-sectional study 115 volunteers were divided in group 1 (non-hypertensive) [n = 30]; group 2 (hypertensive with systolic blood pressure [SBP] < 140 and diastolic blood pressure [DBP] < 90 mmHg) [n = 54]; group 3 (hypertensive with SBP ≥ 140 or DBP ≥ 90 mmHg) [n = 31] and simultaneous measurements of systemic blood pressure (BP) and middle cerebral artery blood flow velocity (CBFV) were obtained from digital plethysmography and transcranial Doppler. Beat-to-beat, critical closing pressure (CrCP), resistance-area product (RAP) and autoregulation index (ARI) values were extracted by linear regression analysis of instantaneous BP and CBFV waveforms using computerised analysis. Pulsatility index (PI) was calculated and CO2 reactivity was assessed by the breath-holding test. Despite their higher RAP (1.7 [±0.7], p < 0.001) compared to groups 1 and 2, uncontrolled hypertensive using diuretics (p = 0.047) and α2-agonists (p = 0.009) had significantly lower PI. Impaired CO2 reactivity was common between the two hypertensive groups (p = 0.008), however ARI, CrCP and CBFV did not differ between them and non-hypertensive individuals and also did not correlate with any AHD used. Unlike the RAP, PI does not seem to reflect the real cerebrovascular resistence resulting from chronic arterial remodelling. Despite impaired CO2 reactivity, hypertensivehavearterial tonus and CA comparable to non-hypertensive. Experimental studies involving an untreated hypertensive control group are required to robustly make definitive conclusions about these questions.

Fiber Bragg Grating Pulse and Systolic Blood Pressure Measurement System Based on Mach-Zehnder Interferometer.

A fiber Bragg grating (FBG) pulse and systolic blood pressure (SBP) measurement system based on the edge-filtering method is proposed. The edge filter is the Mach-Zehnder interferometer (MZI) fabricated by two fiber couplers with a linear slope of 52.45 dBm/nm. The developed system consists of a broadband light source, an edge filter, fiber Bragg gratings (FBGs), a coarse wavelength-division multiplexer (CWDM), and signal-processing circuits based on a field-programmable gate array (FPGA). It can simultaneously measure pulse pulsations of the radial artery in the wrist at three positions: Cun, Guan and Chi. The SBP can be calculated based on the pulse transit time (PTT) principle. The measurement results compared to a standard blood pressure monitor showed the mean absolute error (MAE) and standard deviation (STD) of the SBP were 0.93 ± 3.13 mmHg. The system meets the requirements of the Association for the Advancement of Medical Instrumentation (AAMI) equipment standards. The proposed system can achieve continuous real-time measurement of pulse and SBP and has the advantages of fast detection speed, stable performance, and no compression sensation for subjects. The system has important application value in the fields of human health monitoring and medical device development.

Effects of acupuncture on endothelial active factors and related autonomic neurotransmitters in spontaneous hypertension rats

To observe the effects of acupuncture at "antihypertensive acupoint prescription" on endothelial active factors and related autonomic neurotransmitters in spontaneous hypertension rats, and explore the vascular regulation and central regulation mechanisms of acupuncture for anti-hypertension. Thirty SPF grade male spontaneous hypertension rats were randomly divided into a model group (15 rats) and an acupuncture group (15 rats). Besides, 15 Wistar Kyoto rats were collected as a blank control group (normal group). In the acupuncture group, acupuncture was delivered at the "antihypertensive acupoint prescription" (bilateral "Renying" [ST 9], "Quchi" [LI 11], "Zusanli" [ST 36], "Taichong" [LR 3] and "Neiguan" [PC 6]), with needles retained for 30 min, once daily. The duration of intervention was 28 days. Every week, using the the irritation scale, the sign of sympathetic irritation was evaluated dynamically. The arterial blood pressure of the rats tail was determined, using non-invasive blood pressure measurement system. ELISA was adopted to detect the levels of calcitonin gene-related peptide (CGRP), nitric oxide (NO), endothelin-1 (ET-1), neuropeptide Y (NPY) in the serum. DAB chromogenic in situ hybridization (CISH) was provided to detect the mRNA expression of endothelial nitric oxide synthase (eNOS) in the internal carotid artery and the arcuate nucleus (ARC), and that of CGRP in the paraventricular nucleus posterior (PVP) and the ventrolateral medulla (VLM). Liquid chromatography-mass spectrometry (LC-MS) was used to detect the levels of epinephrine (E) and norepinephrine (NE) in the paraventricular nucleus anterior (PVA). Compared with the normal group, the irritation scores, systolic blood pressure and diastolic blood pressure were increased at each time point in the model group (P<0.05). When compared with the model group, the irritation scores after the intervention for 3 and 4 weeks, and systolic and diastolic blood pressure after intervention for 2, 3 and 4 weeks were reduced in the acupuncture group (P<0.05). In comparison with the normal group, the serum CGRP and NO levels of the rats were decreased (P<0.05), and the serum ET-1 and NPY levels, as well as E and EN levels in PVA were increased (P<0.05) in the model group. The levels of serum CGRP and NO were elevated (P<0.05), and the serum ET-1 and NPY levels, as well as E and EN levels of PVA were reduced (P<0.05) in the acupuncture group when compared with those of the model group. In the model group, the media of internal carotid artery exhibited thickening and remodeling, while the neuron volume in ARC was small. In the acupuncture group, every layer of internal carotid artery was acceptably arranged, and the parvicellular neuron of ARC was moderate in volume. For the in situ hybridization of eNOS mRNA for the rats of each group, the smooth muscle cells were predominantly expressed in each layer of the internal carotid artery, whereas the expression of parvicellular neurons was dominated in ARC. In the model group, the large and small neurosecretory cells were distributed sparsely in the nerves of PVP; in the acupuncture group, the cells of these two species were distributed regularly; and there were few species of glial cell in the VLM of either the model group or the acupuncture group. In each group, for the in situ hybridization of CGRP mRNA, the small neurosecretory cells were expressed predominately in the PVP, while, the expression of glial cell nuclei and the cell cytoplasm was dominated in the VLM. Compared with the normal group, the mRNA expression of eNOS in the internal carotid artery and ARC and that of CGRP mRNA in the PVP and VLM was decreased in the model group (P<0.05). In the acupuncture group, when compared with the model group, the mRNA expression of eNOS in the internal carotid artery and ARC and that of CGRP in the PVP and VLM was increased in the acupuncture group (P<0.05). Acupuncture at "antihypertensive acupoint prescription" can upregulate the level of vascular relaxing factors, downregulate the level of contracting factors, enhance the response of relaxing factors in targeting blood vessels and regulating the center. The mechanism may be related to the modulation of the sympathetic-adrenergic autonomic neurotransmitters in the paraventricular nucleus in spontaneous hypertension rats.

A Wireless Noninvasive Blood Pressure Measurement System Using MAX30102 and Random Forest Regressor for Photoplethysmography Signals

Hypertension, often termed “the silent killer”, is associated with cardiovascular risk and requires regular blood pressure (BP) monitoring. However, existing methods are cumbersome and require medical expertise, which is worsened by the need for physical contact, particularly during situations such as the coronavirus pandemic that started in 2019 (COVID-19). This study aimed to develop a cuffless, continuous, and accurate BP measurement system using a photoplethysmography (PPG) sensor and a microcontroller via PPG signals. The system utilizes a MAX30102 sensor and ESP-WROOM-32 microcontroller to capture PPG signals that undergo noise reduction during preprocessing. Peak detection and feature extraction algorithms were introduced, and their output data were used to train a machine learning model for BP prediction. Tuning the model resulted in identifying the best-performing model when using a dataset from six subjects with a total of 114 records, thereby achieving a coefficient of determination of 0.37/0.46 and a mean absolute error value of 4.38/4.49 using the random forest algorithm. Integrating this model into a web-based graphical user interface enables its implementation. One probable limitation arises from the small sample size (six participants) of healthy young individuals under seated conditions, thereby potentially hindering the proposed model’s ability to learn and generalize patterns effectively. Increasing the number of participants with diverse ages and medical histories can enhance the accuracy of the proposed model. Nevertheless, this innovative device successfully addresses the need for convenient, remote BP monitoring, particularly during situations like the COVID-19 pandemic, thus making it a promising tool for cardiovascular health management.

Accurate Blood Pressure Measurement Using Smartphone's Built-in Accelerometer

Efficient blood pressure (BP) monitoring in everyday contexts stands as a substantial public health challenge that has garnered considerable attention from both industry and academia. Commercial mobile phones have emerged as a promising tool for BP measurement, benefitting from their widespread popularity, portability, and ease of use. Most mobile phone-based systems leverage a combination of the built-in camera and LED to capture photoplethysmography (PPG) signals, which can be used to infer BP by analyzing the blood flow characteristics. However, due to low Signal-to-Noise (SNR), various factors such as finger motion, improper finger placement, skin tattoos, or fluctuations in environmental lighting can distort the PPG signal. These distortions consequentially affect the performance of BP estimation. In this paper, we introduce a novel sensing system that utilizes the built-in accelerometer of a mobile phone to capture seismocardiography (SCG) signals, enabling accurate BP measurement. Our system surpasses previous mobile phone-based BP measurement systems, offering advantages such as high SNR, ease of use, and power efficiency. We propose a triple-stage noise reduction scheme, integrating improved complete ensemble empirical mode decomposition with adaptive noise (ICEEMDAN), recursive least squares (RLS) adaptive filter, and soft-thresholding, to effectively reconstruct high-quality heartbeat waveforms from initially contaminated raw SCG signals. Moreover, we introduce a data augmentation technique encompassing normalization coupled with temporal-sliding, effectively augmenting the diversity of the training sample set. To enable battery efficiency on smartphone, we propose a resource-efficient deep learning model that incorporates resource-efficient convolution, shortcut connections, and Huber loss. We conduct extensive experiments with 70 volunteers, comprising 35 healthy individuals and 35 individuals diagnosed with hypertension, under a user-independent setting. The excellent performance of our system demonstrates its capacity for robust and accurate daily BP measurement.

A Novel Contactless Blood Pressure Measurement System and Algorithm Based on Vision Intelligence

The measurement of vital signs such as blood pressure plays a key role in human health. Usually, we encounter some problems when we check them in the traditional way; for example, it is impossible to check continuously, and measuring vital signs requires direct contact with the patient, which can be uncomfortable for certain individuals. In this research, we present a vision-based system for estimating blood pressure using pulse transit time (PTT) and the Eulerian video magnification (EVM) technique to amplify tiny color variations caused by blood flow to calculate arterial pulse waves traveling between two arterial sites. Calculating the PTT by processing the video signal for each subject, an oscillometer BP device was used to evaluate the performance between measurements in different conditions, including rest, exercise, and during recovery. Mean systolic BP was 115 mmHg at rest, 137 mmHg during high-intensity exercise, and 114 mmHg during recovery, respectively. The average value of diastolic blood pressure did not change significantly before, during, and after exercise. When we compared the systolic and diastolic blood pressure with ground-truth results, our system showed an accuracy of 91% for systolic blood pressure and 90% for diastolic blood pressure.

Pulse wave analysis measurements: important, underestimated and undervalued parameters in cardiovascular health problems.

Central aortic stiffness is established as a reliable measure of cardiovascular disease. While pulse wave velocity (PWV) analysis measures arterial distensibility, risk profile of cardiovascular diseases can be expanded with following pulse wave analysis measurements: central aortic systolic blood pressure (CABPS), central aortic pulse pressure (CAPP), central aortic reflection magnitude (CARM), central aortic augmented pressure (CAAP) and central aortic augmentation index (CAAIx). The aim of this study is to evaluate the clinical usefulness and importance of pulse wave analysis measurements in specific cardiovascular conditions and diseases, both in term of diagnosis and therapeutic monitoring. One thousand sixty-six subjects were included. According to age bracket, four cohorts were investigated-healthy subjects (NL), hypertensive patients (HP), ischemic heart disease (IHD) and valvular heart disease (VHD) patients. Arterial stiffness was analyzed through Sphygmocor XCEL Central Blood Pressure Measurement System and Sphygmocor XCEL PWV Measurement System. Furthermore we observed the pulse wave analysis measurements of 14 patients with diagnose of ADHD who were referred by a child psychiatrist, in order to investigate the initiation of methylphenidate treatment. Statistically significant differences were found between NL and HP cohorts, across almost all age brackets, regarding pulse wave analysis measurements. In the risk stratification of arterial stiffness hypertension and especially central aortic blood pressure systolic (CABPS) seems a determining factor. Pulse wave analysis measurements for IHD and VHD cohort comparisons with NL counterparts, revealed non- statistically significant variations. Elevated CAAP, CAAIx and CARM within the youngest age group (0-10 years) in attention-deficit-hyperactivity-disorder (ADHD) patients warrant attention. Following such investigations, CABPS appears as a robust predominant factor in problems of arterial stiffness. Pulse wave analysis and PWV are important parameters in the evaluation and monitoring of arterial hypertension and cardiovascular diseases. There is a hypothesis that CAAP could be an important and even decisive parameter in the diagnosis of ADHD. Further investigation needed.

Evaluation of right ventricular diastolic function, systolic function, and circulating galectin-3 concentrations in dogs with pulmonary stenosis.

Cardiovascular diseases with increased right ventricular (RV) afterload induce RV diastolic and systolic dysfunction, and myocardial fibrosis in humans. Studies in dogs with pulmonary stenosis (PS) evaluating RV diastolic function and markers of myocardial fibrosis are lacking. Dogs with PS have echocardiographic evidence of RV diastolic and systolic dysfunction and increased serum concentrations of galectin-3 (Gal-3), a surrogate biomarker for myocardial fibrosis. Forty client-owned dogs (10 controls, 30 with PS). Prospective study. All dogs had systemic blood pressure measurement, serum biochemical analysis, echocardiography, and measurement of serum Gal-3 concentration performed. Variables of RV diastolic function were obtained in 39/40 dogs. Trans-tricuspid flow velocity in early diastole to trans-tricuspid flow velocity in late diastole ratios (RV E/A) were lower (P < .001) in dogs with PS (median, 0.94; range, 0.62-2.04) compared to controls (1.78; 1.17-2.35). Trans-tricuspid flow velocity in early diastole to tricuspid annular myocardial velocity in early diastole ratios (RV E/e') were higher (P < .001) in dogs with PS (11.55; 4.69-28) compared to control (6.21; 5.16-7.21). Variables of RV systolic function were lower in dogs with PS (P = <.001). Serum Gal-3 concentration was higher (P = .002) in dogs with PS (285.1 pg/mL; 94.71-406.97) compared to control dogs (162.83 pg/mL; 52.3-232.82). Dogs with PS have RV diastolic and systolic dysfunction, and increased Gal-3 concentrations. These findings suggest the presence of RV myocardial fibrosis in dogs with PS, which could impact clinical management.

A new system for cuffless blood pressure measurement

High blood pressure (HBP) increases the risk of cardiovascular, brain, and renal diseases which can lead to severe illness and death. Due to the variability of BP values at different times during the day, continuous BP measurement would allow more effective early diagnosis of elevated blood pressure, and aid in the management of treatment. Various techniques have been proposed for cuffless BP measurement, often relying on the estimation of pulse transit time (PTT) to infer BP. However, challenges such as computational complexity and limited availability of BP monitoring sensors hinder the reliable and widespread implementation of continuous BP measurement. The proposed wristwatch-based system uses speech sounds together with photoplethysmogram (PPG) and electrocardiogram (ECG) signals, and uses a mathematical model which estimates the systolic BP (SBP) and diastolic BP (DBP) from these inputs.We have obtained Pearson correlation coefficient (PCC)s of 0.6094 for systolic BP and 0.6001 for diastolic BP in these experiments. The mean average errors (MAE) obtained are 8.06 mmHg for systolic BP and 7.48 mmHg for diastolic BP, respectively. This study provides meaningful results based on experimental outputs, demonstrating the feasibility of using speech signals in conjunction with PPG and ECG signals for BP estimation. The simplicity of our mathematical model enables efficient and practical implementation in real-time BP monitoring. As a pilot study, our work establishes a foundation for further research, emphasizing the need for enhancing accuracy and reliability, expanding the dataset, and exploring additional physiological parameters to advance continuous BP estimation.Our findings advance the development of cuffless BP monitoring, and address the computational complexity and real-time processing requirements. Future studies should build upon our work to refine and optimize the proposed approach, ultimately leading to improved continuous BP estimation in diverse populations.

Remote Bio Vision: Perfusion Imaging Based Non-Contact Autonomic Biosignal Measurement Algorithm

Due to the outbreak of new viruses in recent years, the need for contactless medical systems has significantly increased for monitoring, treating, managing, and preventing diseases. Systems are constantly being developed to replace conventional biosignal measuring methods with contactless medical systems. Several systems that substitute attachable sensors in conventional systems have been developed to measure diverse biosignals using images captured with visible cameras. Most non-contact biometric systems have certain limitations, for example, they can only measure a single biosignal, such as the heart rate, oxygen saturation, or blood pressure. They are also easily affected by external factors such as lighting conditions and noises. Furthermore, a blood pressure measuring system based on the pulse transit time requires physical contact and accuracy depends on the measurement location. This study examined a system that provides highly accurate biosignals to overcome these limitations of conventional biosignal measurement systems. This study proposes a biosignal measurement system that uses an infra-red camera to reduce visible light noise. The proposed system uses light sources outside the visible range and measures the amplified reflected light using a near infra-red camera to calculate the heart rate and oxygen saturation. The blood flow value is calculated by the measured heart rate and oxygen saturation. Based on measured data, blood pressure is estimated without contact with the body. We compared the proposed system with an existing non-contact blood pressure measurement system. The proposed system showed an average error rate of 2.07% in blood pressure measurement, which increased by 3.86% compared to the conventional system. Also, this study enabled the early detection of pressure ulcers, which is difficult to measure quantitatively.

ANALISIS SISTEM KERJA DAN PENGARUH NON INVASIVE BLOOD PRESSURE PADA PATIENT MONITOR

Patient Monitor is a device that monitors physiological conditions in the form of NIBP (Non-Ivasive Blood Pressure) blood pressure, temperature, respiration, SPO2 and the shape of the heart pulse continuously. The purpose of this study was to find out how the system works and the use of Non Iinvasive Blood Pressure is good in order to get maximum results. This research is a descriptive and qualitative method, namely by analyzing the Work System and the Effect of Noun Invasive Blood Pressure measurement on the Patient Monitor. The results obtained are the NIBP working system on the patient monitor device consisting of power supply, motor, air valve, microprocessor, display. The blood pressure measurement system uses a cuff with air pressure generated by a motor. The conclusion of this study is that the NIBP works using a pneumatic system, namely using air pressure, where the cuff is inflated until the pressure reaches a maximum above systolic pressure, where the arteries are effectively blocked. Then the cuff pressure is reduced to a constant level, the pressure traducer provides an analog signal to the digital hardware during the process of obtaining the systolic, diastolic and mean pressures.

Mathematical Modeling and Numerical Simulation of a Single-Turn MEMS Piezoresistive Pressure Sensor for Enhancement of Performance Metrics

Micro-Electro-Mechanical System (MEMS)-based pressure sensors operating on the principle of piezoresistivity have found profound application in various fields like automobile, aerospace, aviation, biomedical and consumer electronics. Various research studies have been conducted to optimize the design of MEMS-based pressure sensors to meet specific requirements of different fields. Modification in the structure of the piezoresistors placed on these sensors has shown great effect in this regard. However, most of these improvements have been validated through fabrication and measurement, but there has been a lack of significant studies developing analytical models to explain these improvements. This paper studies the performance of a single-turn piezoresistor design on a square silicon diaphragm. The analytical model relates the dimensions of the single-turn piezoresistor on a square diaphragm to the output voltage, and hence, sensor sensitivity is laid out. The correctness of the relation is also validated through Finite Element Analysis (FEA) performed using COMSOL Multiphysics software. Hence, an optimized single-turn design is presented which achieves a sensitivity of 203.57[Formula: see text]mV/V/MPa over a pressure range of 0–1[Formula: see text]MPa. These results are then compared to work from existing literature. The comparison shows an improved performance which was achieved by optimizing the design through its derived analytical model. The proposed sensor can be utilized in disposable blood pressure measurement system where high sensor sensitivity is required.

A Machine Learning Approach to the Non-Invasive Estimation of Continuous Blood Pressure Using Photoplethysmography

Blood pressure is an important vital sign that sometimes requires continuous measurement. The current methods include cuff measurements (manual auscultation and oscillometric techniques) for non-continuous measurement and invasive arterial cannulation for continuous measurement. The use of photoplethysmography as a cuffless, non-invasive, and continuous blood pressure measurement system is investigated through the use of four neural networks. These predict the systolic blood pressure, diastolic blood pressure, mean arterial blood pressure, and waveform shape. The models are trained on 890 h of data from 1669 patients in the MIMIC-III database. Feature-trained artificial neural networks predict the systolic blood pressure to 5.26 ± 6.53 mmHg (mean error ± standard deviation), the diastolic blood pressure to 2.96 ± 3.31 mmHg, and the mean arterial pressure to 3.27 ± 3.55 mmHg. These are used to shift and scale the predicted waveform, allowing the waveform prediction neural network to optimise for the wave shape rather than the amplitude. The waveform prediction has 86.4% correlation with the actual arterial blood pressure waveform. All results meet international clinical blood pressure measurement standards and could potentially change how blood pressure is measured in both clinical and research settings. However, more data from healthy individuals and analysis of the models’ biases based on clinical features is required.

Evaluation of early arterial wall lesions by elastography parameters in spontaneously hypertensive rats

BackgroundArterialsclerosis caused by hypertension can lead to many complications, such as heart attack, stroke and so on. Early diagnosis and treatment of arterialsclerosis can prevent cardiovascular and cerebrovascular diseases and improve the prognosis. The present study aimed to explore the value of ultrasonography in evaluating the early lesion of the local arterial wall in hypertensive rats and identify useful elastography parameters.MethodsA total of 24 spontaneously hypertensive rats (SHR), 10-, 20-, 30-, and 40-weeks-old, were used in this study, with 6 rats in each group. Blood pressure was recorded using the Animal Noninvasive Blood Pressure Measurement System (Kent company, model CODA, USA), and the local elasticity of the abdominal aorta of rats was measured using a ultrasound diagnostic instrument (VINNO, Suzhou city, China). According to the histopathological results, SHR were divided into two groups: the normal arterial elasticity and the early arterial wall lesions. Mann–Whitney U test was used to compare the differences in elastic parameters and influencing factors between the above two groups, and receiver operating characteristic curve (ROC) was used to analyze and judge the value of each elastic parameter in evaluating early arterial lesions.ResultsA total of 22 cases were divided into two groups: 14 in the normal arterial elasticity and 8 in the early arterial wall lesions. The differences in age, blood pressure, pulse wave velocity (PWV), compliance coefficient (CC), distensibility coefficient (DC), and elasticity parameter (EP) between the two groups were compared. The differences in PWV, CC, DC and EP were statistically significant. Subsequently, the ROC curve analysis was performed for the above four evaluation indexes of arterial elasticity; the results were as follows: the area under the curve of PWV, CC, DC, and EP was 0.946, 0.781, 0.946, and 0.911, respectively.ConclusionsEarly arterial wall lesions can be evaluated by ultrasound measurement of local PWV. PWV and DC can accurately evaluate the early arterial wall lesions in SHR, and the combined application of the two can improve the sensitivity and specificity of the approach.

Development of Real-Time Cuffless Blood Pressure Measurement Systems with ECG Electrodes and a Microphone Using Pulse Transit Time (PTT).

Research has shown that pulse transit time (PTT), which is the time delay between the electrocardiogram (ECG) signal and the signal from a photoplethysmogram (PPG) sensor, can be used to estimate systolic blood pressure (SBP) and diastolic blood pressure (DBP) without the need for a cuff. However, the LED of the PPG sensor requires the precise adjustment of both light intensity and light absorption rates according to the contact status of the light-receiving element. This results in the need for regular calibration. In this study, we propose a cuffless blood pressure monitor that measures real-time blood pressure using a microphone instead of a PPG sensor. The blood pulse wave is measured in the radial artery of the wrist using a microphone that can directly measure the sound generated by a body rather than sending energy inside the body and receiving a returning signal. Our blood pressure monitor uses the PTT between the R-peak of the ECG signal and two feature points of the blood pulse wave in the radial artery of the wrist. ECG electrodes and circuits were fabricated, and a commercial microelectromechanical system (MEMS) microphone was used as the microphone to measure blood pulses. The peak points of the blood pulse from the microphone were clear, so the estimated SBP and DBP could be obtained from each ECG pulse in real time, and the resulting estimations were similar to those made by a commercial cuff blood pressure monitor. Since neither the ECG electrodes nor the microphone requires calibration over time, the real-time cuffless blood pressure monitor does not require calibration. Using the developed device, blood pressure was measured three times daily for five days, and the mean absolute error (MAE) and standard deviation (SD) of the SBP and DBP were found to be 2.72 ± 3.42 mmHg and 2.29 ± 3.53 mmHg, respectively. As a preliminary study for proof-of-concept, these results were obtained from one subject. The next step will be a pilot study on a large number of subjects.

Dual wavelength retinal vessel oximetry – influence of fundus pigmentation

BackgroundClinical methods examining oxygenation parameters in humans have been used in many different care settings, but concerns have been raised regarding their clinical utility when assessing people with darker skin pigmentation. While saturation values can be crucial in emergency medicine, they are equally valuable in assessing disease mechanisms and monitoring change in disease progression. Retinal pigmentation varies across individuals and hence, can impact on retinal oxygen parameters. The objective of this study was to quantify and eliminate the impact of retinal pigmentation on retinal vessel oxygen saturation parameters measured in the superficial retinal arterioles and venules.Methods105 healthy individuals of varying skin colour, iris colour and heritage were included. Following a full eye exam to exclude any ocular abnormality, all participants underwent intraocular pressure, systemic blood pressure measurements and dilated dual wavelength retinal photography. Rotation matrices were employed to minimise the dependency of retinal pigmentation on arterial and venous oxygen saturation measurements determined in a concentric measurement annulus.ResultsRetinal oxygen saturation in venules showed a linear correlation with retinal pigmentation (y = 0.34 × x + 38.598), whereas arterial saturation followed a polynomial pattern (y = 0.0089 × x2 + 0.7499 × x + 85.073). Both arterial and venous saturation values were corrected using local fundus pigmentation. Pre-correction retinal arterial and venous oxygen saturation were 89.0% (±13.1) and 43.7% (±11.5), respectively, and post- correction values were 94.8% (±8.7) for arteries and 56.3% (±7.0) veins.ConclusionsWhen assessing multi-ethnic cohorts, it is important to consider the impact of pigmentation on imaging parameters and to account for it prior to clinical interpretation.

Higher Order Derivative-Based Integrated Model for Cuff-Less Blood Pressure Estimation and Stratification Using PPG Signals

Precise blood pressure (BP) estimation is vital for diagnosing arterial hypertension and other cardiovascular ailments. The photoplethysmogram (PPG)-based cuff-less BP measurement is an alternative to the traditional cuff-based systems. The morphological, temporal, and frequency-domain-based features have been used for BP estimation in the PPG-based BP measurement systems. However, dealing with varying signal morphology and feature dependency on the fiducial points in PPG contours remains challenging and limits the performance of the existing BP estimation algorithms, especially in wearable devices. This work presents a novel approach that considers the nonlinear features of PPG signals evaluated using higher order derivatives. In particular, the PPG signal’s third and fourth derivative contours are used to extract features, such as fractal dimension, bubble entropy (BE), Lyapunov exponent, and moving slope. Machine learning algorithms such as random forest (RF), extreme gradient boosting (XGBoost), and support vector regression (SVR) models are used for BP estimation using the nonlinear features of PPG signals. The estimated BP values are further categorized based on five broad classes based on the BP stratification criteria such as hypotension, normal, prehypertension, stage-I, and stage-II hypertension, respectively. The performance of the suggested approach is evaluated using PPG signals from three publicly available databases (multiparameter intelligent monitoring in intensive care (MIMIC)-I, II, and III). The proposed estimation approach has outperformed the recent existing algorithms and achieved a minimum value of mean absolute error (MAE) ± standard deviation (STD) in (systolic BP (SBP) and diastolic BP (DBP) values) as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${0}.{74}\pm {2}.{42}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${0}.{35} \pm {1}.{06}$ </tex-math></inline-formula> , respectively, for the MIMIC-I database. The suggested approach has also achieved grade-A on the British Hypertension Society (BHS) standard.

Behavioral and cardiovascular effects of a single dose of gabapentin or melatonin in cats: a randomized, double-blind, placebo-controlled trial.

The aim of this study was to verify whether a single oral dose of gabapentin (100 mg) or melatonin (3 mg) given 60 mins before a cardiac evaluation would reduce anxiety without interfering with heart rate (HR), systemic blood pressure (SBP), electrocardiogram (ECG) and echocardiographic indexes. Seventy-five client-owned healthy cats underwent two sets of cardiac assessments 60 mins apart, randomly divided into gabapentin, melatonin and placebo groups. The interval between treatment and the second ECG and SBP measurement was 60 mins, and 70 mins for echocardiography. A compliance score (CS) classified the behavior, focusing on the ease of handling. Most variables did not change between the examinations. The placebo group showed more significant changes (SBP, tricuspid annular plane systolic excursion, HR during echocardiography, aortic flow velocity, S' wave from lateral mitral annulus), but they were not considered to be hemodynamically relevant. Gabapentin and melatonin significantly increased the cats' compliance without interfering with cardiac assessment. Eight cats presented with mild sedation, seven after gabapentin and one after melatonin. No major side effects were observed. Gabapentin tranquilized the cats when it was given 60 mins prior to ECG and SBP measurement, and 70 mins prior to echocardiography, without interfering with systolic echocardiographic indexes. Melatonin also decreased the CS, but without sedation in most cases. The waiting period may have relaxed the cats in the placebo group, resulting in lower SBP measurements. However, this tranquility did not last as some echocardiographic changes signaled a sympathetic predominance.

Abstract 14827: Clinical Validation of a Novel Cuffless Portable Blood Pressure Measurement Device

Introduction: Ambulatory blood pressure (BP) measurements using an arm-cuff can be both cumbersome and painful; limiting patients’ willingness to obtain routine measurements. A novel, simple, rapid, cuffless device (TouchBP™) calculates systolic and diastolic BP based on observed blood volume oscillations that result from the variable finger pressure on a custom sensor pad. The accuracy of this novel device relative to cuff based standards is not known. Methods: An independent physiology lab compared a blind TouchBP™ reading to reference SBP and DBP measurements made via an experienced auscultator. Subsequent data from 6 subjects was excluded due to signal artifacts resulting in 52 subjects in the analysis dataset. The Digitouch prediction algorithm was created using data from two previous clinical studies with different subject pools. Results: Among 52 subjects, SBP ranged from 95 to 167 mmHg, and DBP ranged from 58 to 106 mmHg. The SBP estimation error was 0.4 ± 7.9 mmHg, while DBP error was 0.3 ± 7.2 mmHg [bias ± precision]. (See Figure 1). The bias and precision results meet accuracy thresholds established by AAMI standard (bias&lt; 5 mmHg and precision &lt; 8mmHg). Conclusion: Digitouch’s TouchBP™, a novel cuffless mobile BP measurement system produces accuracy results like traditional oscillometric cuffs.