Methodological Role of Mathematics to Estimate Human Blood Pressure Through Biosensors

This paper presents a non-invasive technique and cuff less method for blood pressure measurement with a hardware prototype implementation. The sophisticated feature called pulse transit time (PTT) is extracted and investigated with a development of a smart system which consists of ECG, PPG sensor to estimate the systolic and diastolic blood pressure with support of advanced signal processing methodologies. The proposed method experiments have been carried out in hospital environment and tested with real time patients to validate the proposed method. The maximum error percentage of the proposed system has been shown to be 5.3% of systolic blood pressure (mmHg) and 4.7% of diastolic blood pressure (mmHg). This system also allows the monitoring of patient hypertension and overcome the limitation of cuff-based hospitalized measurement system

Blood Pressure Measurement Device for Low Resource Settings

ME450 Capstone Design and Manufacturing Experience: Fall 2015The design team spent eight weeks in the Obstetrics and Gynecology Department at a tertiary referral hospital, Komfo Anokye Teaching Hospital (KATH), in Kumasi, Ghana. During the team’s immersion experience at the hospital, the team observed healthcare providers experiencing difficulty following obstetrics patients’ blood pressure management plans. This occurred largely because of the high volume of patients and the busyness of the wards. The patient's blood pressure measurement strongly influences the treatment especially if she has hypertensive disorders. Hypertensive disorders, mainly preeclampsia and eclampsia, are the second leading cause of maternal mortality worldwide and the leading cause of maternal mortality at KATH. The team identified an opportunity for the development of a blood pressure measurement device to aid the healthcare providers in measuring the patients’ blood pressures every 30 minutes or four hours according to their management plans. This project is in collaboration with clinical mentors and advisors at University of Michigan Hospital and KATH. The final design is an auscultatory device with a microphone stethoscope and headphones to listen to the Korotkoff sounds, a hand pump for manual inflation, an automatic constant rate deflation facilitated by a solenoid valve, a LCD screen to display the current pressure, a slip-on cuff, an aneroid pressure gauge for calibration, a handle, a storage area, and a rechargeable battery. The current prototype follows the design fairly closely however the device is not powered by a rechargeable battery and the electrical components are all on a breadboard which prevents its portability. All validation testing completed so far on the current prototype has been promising including testing the accuracy and ease-of-use of the device when used by three nursing student. This device will be continued to be improved next semester so that it can be taken to KATH for further validation and feedback.http://deepblue.lib.umich.edu/bitstream/2027.42/117349/1/ME450-F15-Project07-FinalReport.pd

Estimating pulse wave velocity using mobile phone sensors

Pulse wave velocity has been recognised as an important physiological phenomenon in the human body, and its measurement can aid in the diagnosis and treatment of chronic diseases. It is the gold standard for arterial stiffness measurements, and it also shares a positive relationship with blood pressure and heart rate. There exist several methods and devices via which it can be measured. However, commercially available devices are more geared towards working health professionals and hospital settings, requiring a significant monetary investment and specialised training to operate correctly. Furthermore, most of these devices are not portable and thus generally not feasible for private home use by the common individual. Given its usefulness as an indicator of certain physiological functions, it is expected that having a more portable, affordable, and simple to use solution would present many benefits to both end users and healthcare professionals alike. This study investigated and developed a working model for a new approach to pulse wave velocity measurement, based on existing methods, but making use of novel equipment. The proposed approach made use of a mobile phone video camera and audio input in conjunction with a Doppler ultrasound probe. The underlying principle is that of a two-point measurement system utilising photoplethysmography and electrocardiogram signals, an existing method commonly found in many studies. Data was collected using the mobile phone sensors and processed and analysed on a computer. A custom program was developed in MATLAB that computed pulse wave velocity given the audio and video signals and a measurement of the distance between the two data acquisition sites. Results were compared to the findings of previous studies in the field, and showed similar trends. As the power of mobile smartphones grows, there exists potential for the work and methods presented here to be fully developed into a standalone mobile application, which would bring forth real benefits of portability and cost-effectiveness to the prospective user base

Validity Of Withings Pulse Wave Velocity Scale Versus Gold Standard Applanation Tonometry And Body Composition Analysis In A Young Healthy Population

Cardiovascular disease currently is the leading cause of death nationwide. Pulse Wave Velocity (PWV) is now considered a gold standard for measuring arterial health. Deleterious changes in arterial distensibility are risk factors for cardiovascular disease. The Withings Body Cardio Scale has been marketed to the general population for its ability to measure PWV in the home, however, there are no data that demonstrate the accuracy of this technology. The PURPOSE of this study was to determine the accuracy and reproducibility of PWV with the Withings Body Cardio. METHODS 20 normotensive healthy young adults enrolled in this study. Two measurements with each operating system were obtained over a period of 30 minutes. Standing PWV measurements with SphygmoCor were utilized in order to maintain ecological validity with the scale. RESULTS Significant differences were observed in measurement of fat mass and fat-free mass. No significant differences were found between Withings and SphygmoCor equipment. CONCLUSION There were no clinical differences detected between devices in the measurement of PWV, suggesting the home-based system of tracking PWV using the Withings scale can be an accurate measurement of systemic PWV. Monitoring cardiopulmonary health at home can be useful in providing clinical insight for longitudinal healthcare monitoring

Multimodal Photoplethysmography-Based Approaches for Improved Detection of Hypertension

Elevated blood pressure (BP) is a major cause of death, yet hypertension commonly goes undetected. Owing to its nature, it is typically asymptomatic until later in its progression when the vessel or organ structure has already been compromised. Therefore, noninvasive and continuous BP measurement methods are needed to ensure appropriate diagnosis and early management before hypertension leads to irreversible complications. Photoplethysmography (PPG) is a noninvasive technology with waveform morphologies similar to that of arterial BP waveforms, therefore attracting interest regarding its usability in BP estimation. In recent years, wearable devices incorporating PPG sensors have been proposed to improve the early diagnosis and management of hypertension. Additionally, the need for improved accuracy and convenience has led to the development of devices that incorporate multiple different biosignals with PPG. Through the addition of modalities such as an electrocardiogram, a final measure of the pulse wave velocity is derived, which has been proved to be inversely correlated to BP and to yield accurate estimations. This paper reviews and summarizes recent studies within the period 2010-2019 that combined PPG with other biosignals and offers perspectives on the strengths and weaknesses of current developments to guide future advancements in BP measurement. Our literature review reveals promising measurement accuracies and we comment on the effective combinations of modalities and success of this technology

Body sensor networks: smart monitoring solutions after reconstructive surgery

Advances in reconstructive surgery are providing treatment options in the face of major trauma and cancer. Body Sensor Networks (BSN) have the potential to offer smart solutions to a range of clinical challenges. The aim of this thesis was to review the current state of the art devices, then develop and apply bespoke technologies developed by the Hamlyn Centre BSN engineering team supported by the EPSRC ESPRIT programme to deliver post-operative monitoring options for patients undergoing reconstructive surgery. A wireless optical sensor was developed to provide a continuous monitoring solution for free tissue transplants (free flaps). By recording backscattered light from 2 different source wavelengths, we were able to estimate the oxygenation of the superficial microvasculature. In a custom-made upper limb pressure cuff model, forearm deoxygenation measured by our sensor and gold standard equipment showed strong correlations, with incremental reductions in response to increased cuff inflation durations. Such a device might allow early detection of flap failure, optimising the likelihood of flap salvage. An ear-worn activity recognition sensor was utilised to provide a platform capable of facilitating objective assessment of functional mobility. This work evolved from an initial feasibility study in a knee replacement cohort, to a larger clinical trial designed to establish a novel mobility score in patients recovering from open tibial fractures (OTF). The Hamlyn Mobility Score (HMS) assesses mobility over 3 activities of daily living: walking, stair climbing, and standing from a chair. Sensor-derived parameters including variation in both temporal and force aspects of gait were validated to measure differences in performance in line with fracture severity, which also matched questionnaire-based assessments. Monitoring the OTF cohort over 12 months with the HMS allowed functional recovery to be profiled in great detail. Further, a novel finding of continued improvements in walking quality after a plateau in walking quantity was demonstrated objectively. The methods described in this thesis provide an opportunity to revamp the recovery paradigm through continuous, objective patient monitoring along with self-directed, personalised rehabilitation strategies, which has the potential to improve both the quality and cost-effectiveness of reconstructive surgery services.Open Acces

Constraint Latent Space Matters: An Anti-anomalous Waveform Transformation Solution from Photoplethysmography to Arterial Blood Pressure

Arterial blood pressure (ABP) holds substantial promise for proactive cardiovascular health management. Notwithstanding its potential, the invasive nature of ABP measurements confines their utility primarily to clinical environments, limiting their applicability for continuous monitoring beyond medical facilities. The conversion of photoplethysmography (PPG) signals into ABP equivalents has garnered significant attention due to its potential in revolutionizing cardiovascular disease management. Recent strides in PPG-to-ABP prediction encompass the integration of generative and discriminative models. Despite these advances, the efficacy of these models is curtailed by the latent space shift predicament, stemming from alterations in PPG data distribution across disparate hardware and individuals, potentially leading to distorted ABP waveforms. To tackle this problem, we present an innovative solution named the Latent Space Constraint Transformer (LSCT), leveraging a quantized codebook to yield robust latent spaces by employing multiple discretizing bases. To facilitate improved reconstruction, the Correlation-boosted Attention Module (CAM) is introduced to systematically query pertinent bases on a global scale. Furthermore, to enhance expressive capacity, we propose the Multi-Spectrum Enhancement Knowledge (MSEK), which fosters local information flow within the channels of latent code and provides additional embedding for reconstruction. Through comprehensive experimentation on both publicly available datasets and a private downstream task dataset, the proposed approach demonstrates noteworthy performance enhancements compared to existing methods. Extensive ablation studies further substantiate the effectiveness of each introduced module.Comment: Accepted by AAAI-2024, main trac

Photoplethysmography technology use in smart devices for early diagnosis of arterial hypertension: a systematic review

Background: According to the World Health Organisation (WHO), 1 in 4 men and 1 in 5 women have arterial hypertension (AH). It is important to diagnose AH early and constantly monitor blood pressure (BP). We assess the diagnostic accuracy of AH detection using smart devices with photoplethysmography (PPG) and seek to provide guidance from current evidence to clinicians about the value and limitations of their potential use to early diagnose this chronic disease. Material and methods: This systematic review of Medline, Google Scholar, and PubMed databases was conducted according to the PRISMA guidelines. All publications examining any type of AH detection using PPG in smart devices were evaluated. Study quality was assessed using the QUADAS-2 risk of bias tool. Results: The search strategy identified a total of 705 publications, of which 9 studies were included in the systematic review. Of the 9 studies included, 2 used Samsung Galaxy smartphones, and 7 used wearable watch-like devices. A sphygmomanometer was used as a reference standard in all studies. Conclusion: The current evidence base consists of small, biased, and low-quality studies which are insufficient to advise clinicians on the true value of PPG devices for AH detection. Further research is required with reference standards, standardized validation, and transparent algorithms for PPG technology to be used as a valid tool for early AH diagnosis

Enabling Wearable Hemodynamic Monitoring Using Multimodal Cardiomechanical Sensing Systems

Hemodynamic parameters such as blood pressure and stroke volume are instrumental to understanding the pathogenesis of cardiovascular disease. Unfortunately, the monitoring of these hemodynamic parameters is still limited to in-clinic measurements and cumbersome hardware precludes convenient, ubiquitous use. To address this burden, in this work, we explore seismocardiogram-based wearable multimodal sensing techniques to estimate blood pressure and stroke volume. First, the performance of a multimodal, wrist-worn device capable of obtaining noninvasive pulse transit time measurements is used to estimate blood pressure in an unsupervised, at-home setting. Second, the feasibility of this wrist-worn device is comprehensively evaluated in a diverse and medically underserved population over the course of several perturbations used to modulate blood pressure through different pathways. Finally, the ability of wearable signals—acquired from a custom chest-worn biosensor—to noninvasively quantify stroke volume in patients with congenital heart disease is examined in a hospital setting. Collectively, this work demonstrates the advancements necessary towards enabling noninvasive, longitudinal, and accurate measurements of these hemodynamic parameters in remote settings, which offers to improve health equity and disease monitoring in low-resource settings.Ph.D