Accuracy of blood pressure monitoring devices: a critical need for improvement that could resolve discrepancy in hypertension guidelines

Accuracy of cuff blood pressure and systolic blood pressure amplification

Automated cuff measured blood pressure (BP) is the global standard used for diagnosing hypertension, but there are concerns regarding the accuracy of the method. Individual variability in systolic BP (SBP) amplification from central (aorta) to peripheral (brachial) arteries could be related to the accuracy of cuff BP, but this has never been determined and was the aim of this study. Automated cuff BP and invasive brachial BP were recorded in 795 participants (74% male, aged 64 ± 11 years) receiving coronary angiography at five independent research sites (using seven different automated cuff BP devices). SBP amplification was recorded invasively by catheter and defined as brachial SBP minus aortic SBP. Compared with invasive brachial SBP, cuff SBP was significantly underestimated (130 ± 18 mmHg vs. 138 ± 22 mmHg, p < 0.001). The level of SBP amplification varied significantly among individuals (mean ± SD, 7.3 ± 9.1 mmHg) and was similar to level of difference between cuff and invasive brachial SBP (mean difference -7.6 ± 11.9 mmHg). SBP amplification explained most of the variance in accuracy of cuff SBP (R2 = 19%). The accuracy of cuff SBP was greatest among participants with the lowest SBP amplification (ptrend < 0.001). After cuff BP values were corrected for SBP amplification, there was a significant improvement in the mean difference from the intra-arterial standard (p < 0.0001) and in the accuracy of hypertension classification according to 2017 ACC/AHA guideline thresholds (p = 0.005). The level of SBP amplification is a critical factor associated with the accuracy of conventional automated cuff measured BP.

Feasibility of Precision Medicine in Hypertension Management-Scope and Technological Aspects

Personalized management of diseases by considering relevant patient features enables optimal treatment, instead of management according to an average patient. Precision management of hypertension is important, because both susceptibility to complications and response to treatment vary between individuals. While the use of genomic and proteomic personal features for widespread precision hypertension management is not practical, other features, such as age, ethnicity, and cardiovascular diseases, have been utilized in guidelines for hypertension management. In precision medicine, more blood-pressure-related clinical and physiological characteristics in the patient's profile can be utilized for the determination of the threshold of hypertension and optimal treatment. Several non-invasive and simple-to-use techniques for the measurement of hypertension-related physiological features are suggested for use in precision management of hypertension. In order to provide precise management of hypertension, accurate measurement of blood pressure is required, but the available non-invasive blood pressure measurement techniques, auscultatory sphygmomanometry and oscillometry, have inherent significant inaccuracy-either functional or technological-limiting the precision of personalized management of hypertension. A novel photoplethysmography-based technique for the measurement of systolic blood pressure that was recently found to be more accurate than the two available techniques can be utilized for more precise and personalized hypertension management.

Concept, hardware development, and clinical trials of a Galinstan based Mercury free sphygmomanometer: Merkfree

The aim of this work is to develop Merkfree-a mercury-free sphygmomanometer that looks, feels, and operates just like a traditional mercury sphygmomanometer (MS). For this we use Galinstan as a substitute for mercury, which is a non-toxic alloy of Gallium, Indium and Tin. Galinstan is nearly half as dense as mercury and sticks to class. To work with the lower density, we designed an enclosure and scale that is nearly double the length of MS. The issue of stickiness with glass was resolved by maintaining a small meniscus of a reducing agent in the measuring tube and tank of Merkfree. Clinical trials to validate the accuracy of Merkfree against MS and oscillometric sphygmomanometer (OS) were conducted over 252 patients. The results show a good correlation of the systolic and diastolic BP measurements from Merkfree with respect to MS and the OS. The mean absolute percentage error is less than 10% for both SBP and DBP. We also found that Merkfree has lower rounding-off errors compared to MS. Merkfree can be a viable alternative to mercury sphygmomanometer that can help achieve the goal of WHO in eliminating mercury from healthcare, while simultaneously making sure that gold standard technique of sphygmomanometry continues to be available to the clinicians.

Blood pressure measurement using only a smartphone

Hypertension is an immense challenge in public health. As one of the most prevalent medical conditions worldwide, it is a major cause of premature death. At present, the detection, diagnosis and monitoring of hypertension are subject to several limitations. In this review, we conducted a literature search on blood pressure measurement using only a smartphone, which has the potential to overcome current limitations and thus pave the way for long-term ambulatory blood pressure monitoring on a large scale. Among the 333 articles identified, we included 25 relevant articles over the past decade (November 2011–November 2021) and analyzed the described approaches to the types of underlying data recorded with smartphone sensors, the signal processing techniques applied to construct the desired signals, the features extracted from the constructed signals, and the algorithms used to estimate blood pressure. In addition, we analyzed the validation of the proposed methods against reference blood pressure measurements. We further examined and compared the effectiveness of the proposed approaches. Among the 25 articles, 23 propose an approach that requires direct contact between the sensor and the subject and two articles propose a contactless approach based on facial videos. The sample sizes in the identified articles range from three to 3000 subjects, where 8 articles used sample sizes of 85 or more subjects. Furthermore, 10 articles include hypertensive subjects in their participant pools. The methodologies applied for the evaluation of blood pressure measurement accuracy vary considerably among the analyzed articles. There is no consistency regarding the methods for blood pressure data collection and the reference blood pressure measurement and validation. Moreover, no established protocol is currently available for the validation of blood pressure measuring technologies using only a smartphone. We conclude the review with a discussion of the results and with recommendations for future research on the topic.

Arterial hypertension

Arterial hypertension is the most important contributor to the global burden of disease; however, disease control remains poor. Although the diagnosis of hypertension is still based on office blood pressure, confirmation with out-of-office blood pressure measurements (ie, ambulatory or home monitoring) is strongly recommended. The definition of hypertension differs throughout various guidelines, but the indications for antihypertensive therapy are relatively similar. Lifestyle adaptation is absolutely key in non-pharmacological treatment. Pharmacologically, angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, calcium channel blockers, and diuretics are the first-line agents, with advice for the use of single-pill combination therapy by most guidelines. As a fourth-line agent, spironolactone should be considered. The rapidly evolving field of device-based therapy, especially renal denervation, will further broaden therapeutic options. Despite being a largely controllable condition, the actual rates of awareness, treatment, and control of hypertension are disappointingly low. Further improvements throughout the process of patient screening, diagnosis, treatment, and follow-up need to be urgently addressed.

Auscl-D: a mercury-free digital auscultatory sphygmomanometer

More than quarter of world's population is consumed by hypertension, leading to premature death of thousands of people per year across the globe. One of the major reasons behind hypertension misdiagnosis is inaccurate blood pressure (BP) measurements, which can be attributed to various human or instrumentation errors. Currently used BP measuring sphygmomanometers, suffers from poor reliability, performance deterioration over time or are unable to meet environmental protection protocols. In this article, we propose a low-cost, highly portable, light-weight, easily manufacturable, battery operated, mercury free, auscultation based digital sphygmomanometer - Auscl-D, for easy and accurate BP measurements. The proposed device can be made from easily available components with cheap manufacturing processes available throughout globe, even in remote areas. The device demonstrated to have accuracy comparable to mercury sphygmomanometer, which is the gold-standard for BP measurements. The preliminary clinical trials were conducted at Dayanand Medical College & Hospital (DMCH) (Ludhiana, India), to compare the performance of proposed device with commonly used aneroid sphygmomanometers employing the auscultatory method and validated oscillometric sphygmomanometers from MicroLife. The test results show good agreement for systolic and diastolic BP measurements taken using Auscl-D device compared to the aneroid and oscillometric types. This shows the potential of proposed design to serve as low-cost, highly portable replacement for conventionally used sphygmomanometers, without the toxicity and reliability issues.

A survey to gauge confidence of Indian clinicians on three primary devices for blood pressure measurement

PURPOSE

As per its commitment at Minamata convention, and in line with other developed economies, the Indian government is set to ban the use of mercury sphygmomanometers by end of the year 2020. However, the Mercury sphygmomanometer is still widely used by clinicians in India. We conducted a survey to gauge the confidence of Indian clinicians on three primary devices of blood pressure (BP) measurement - mercury sphygmomanometer, aneroid sphygmomanometer and automatic digital BP monitor.

MATERIALS AND METHODS

We conducted an anonymous online survey through various clinician forums asking questions related to accuracy, reliability and expectations from BP monitors.

RESULTS

A total of 139 responses were received from clinicians across specialties. The results show that more than 80% of clinicians believe that mercury sphygmomanometers are the most accurate and nearly 50% find it most reliable. For most respondents, accuracy is the most important parameter and convenience of use and portability are secondary considerations. If a mercury-free sphygmomanometer is offered with the same accuracy and reliability, 88% of respondents said they are willing to buy it.

CONCLUSIONS

Mercury sphygmomanometer is still perceived favorably over other non-mercury alternatives by most Indian clinicians. Validated oscillometric devices should be promoted to bring about change in the perspectives of clinicians towards adopting non-mercury alternatives of BP measurement in India.

Compensatory depression of arterial pressure and reversal of ECG abnormalities by Annona muricata and Curcuma longa in hypertensive Wistar rats

OBJECTIVES

Increasing hypertension incidence in Sub-Sahara Africa and the current cost of management of the metabolic disorder has necessitated research on medicinal plants employed in African Traditional Medicine for hypertension. Thus, this study evaluated antihypertensive effect of Annona muricata leaves or Curcuma longa rhizomes in experimentally-induced hypertensive male Wistar rats (n=70) which were unilaterally nephrectomized and daily loaded with 1% salt. Cardiovascular and haematological changes, as well as urinalysis were determined.

METHODS

Rats were uninephrectomized and NaCl (1%) included in drinking water for 42 days. Extract-treated hypertensive rats were compared to normotensive, untreated hypertensive and hypertensive rats treated with lisinopril (5 mg/70 kg) or hydrochlorothiazide (12.5 mg/70 kg). A. muricata extract or C. longa extract were administered at 100, 200 or 400 mg/kg. Blood pressure (systolic, diastolic and mean arterial) and electrocardiogram was measured on day 41. Twenty-four-hour urine samples were collected from day 42. Blood samples were collected on day 43 for haematology (PCV, red cell indices, WBC and its differentials, and platelets).

RESULTS AND CONCULSIONS

A. muricata or C. longa extracts caused a decline in elevated blood pressure of hypertensive rats. Heart rate and QT segment reduction coupled with prolonged QRS duration were reversed in extract-treated rats, with significant increases in hemogram parameters indicating increased blood viscosity. Also, leukocyturia, proteinuria and ketonuria with increased urine alkalinity, urobilinogen and specific gravity which are classical indicators of poor prognostic outcomes in hypertension were reversed in extract-treated rats. In conclusion, A. muricata and C. longa have cardioprotective effect with reversal of derangements in haemogram and urinalysis associated with hypertension.

Cuff Under Pressure for Greater Accuracy

PURPOSE OF REVIEW

To present the evidence that describes what is being measured by upper-arm cuff blood pressure (BP) and the level of accuracy compared with invasive central aortic and brachial BP. Potential causes of inaccuracy and emerging methods are also discussed.

RECENT FINDINGS

On average cuff systolic BP systematically underestimates invasive brachial systolic BP, although in a given individual it may substantially under- or over-estimate central aortic systolic BP. Such errors may affect individual health management outcomes and distort population level data on hypertension prevalence and control. Oscillometric cuff BP is particularly susceptible to inaccuracy in people with high arterial stiffness and with pathophysiological BP waveform shapes. Emerging cuff-less BP methods will be susceptible to inaccuracy if oscillometric cuff BP is used for calibration. The original purpose of cuff BP was to estimate central aortic BP. Recent evidence has shown substantial inaccuracy of oscillometric cuff BP exists for the measurement of invasive central aortic and brachial BP. Thus, development of more accurate BP methods, through better understanding of oscillometric and BP waveform morphology, is needed to improve health outcomes related to high BP.

Agreement and Reliability of Clinician-in-Clinic Versus Patient-at-Home Clinical and Functional Assessments: Implications for Telehealth Services

Objective

To compare agreement and reliability between clinician-measured and patient self-measured clinical and functional assessments for use in remote monitoring, in a home-based setting, using telehealth.

Design

Reliability study: repeated-measure, within-subject design.

Setting

Trained clinicians measured standard clinical and functional parameters at a face-to-face clinic appointment. Participants were instructed on how to perform the measures at home and to repeat self-assessments within 1 week.

Participants

Liver transplant recipients (LTRs) (N=18) (52±14y, 56% men, 5.4±4.3y posttransplant] completed the home self-assessments.

Interventions

Not applicable.

Main Outcome Measures

The outcomes assessed were body weight, systolic and diastolic blood pressure (SBP and DBP), waist circumference, repeated chair sit-to-stand (STST), maximal push-ups, and the 6-minute walk test (6MWT). Intertester reliability and agreement between face-to-face clinician and self-reported home-based participant measures were determined by intraclass-correlation coefficients (ICCs) and Bland-Altman plots, which were compared with minimal clinically important differences (MCID) (determined a priori).

Results

The mean difference (95% confidence interval) and [limits of agreement] for measures (where positive values indicate lower participant value) were weight, 0.7 (0.01-1.4) kg [−2.2 to 3.6kg]; waist 0.4 (−1.2 to 2.0) cm [−5.9 to 6.8cm]; SBP 7.7 (0.6-14.7 ) mmHg [−19.4 to 34.9mmHg]; DBP 2.4 (−1.4 to 6.2 ) mmHg [−12.2 to 17.0mmHg]; 6MWT, 7.5 (−29.1 to 44.1) m [−127.3 to 142.4m]; STST 0.5 (−0.8 to 1.7) seconds [−4.3 to 5.3s]; maximal push-ups −2.2 (−4.4 to −0.1) [−10.5 to 6.0]. ICCs were all >0.75 except for STST (ICC=0.73). Mean differences indicated good agreement than MCIDs; however, wide limits of agreement indicated large individual variability in agreement.

Conclusions

Overall, LTRs can reliably self-assess clinical and functional measures at home. However, there was wide individual variability in accuracy and agreement, with no functional assessment being performed within acceptable limits relative to MCIDs >80% of the time.

[Lancet Commission on Hypertension Group position statement on the global improvement of accuracy standards for devices that measure blood pressurePosicionamento do Grupo da Lancet Commission on Hypertension sobre a melhoria global dos padrões de acurácia para aparelhos que medem a pressão arterial]

The Lancet Commission on Hypertension identified that a key action to address the worldwide burden of high blood pressure (BP) was to improve the quality of BP measurements by using BP devices that have been validated for accuracy. Currently, there are over 3 000 commercially available BP devices, but many do not have published data on accuracy testing according to established scientific standards. This problem is enabled through weak or absent regulations that allow clearance of devices for commercial use without formal validation. In addition, new BP technologies have emerged (e.g. cuffless sensors) for which there is no scientific consensus regarding BP measurement accuracy standards. Altogether, these issues contribute to the widespread availability of clinic and home BP devices with limited or uncertain accuracy, leading to inappropriate hypertension diagnosis, management and drug treatment on a global scale. The most significant problems relating to the accuracy of BP devices can be resolved by the regulatory requirement for mandatory independent validation of BP devices according to the universally-accepted International Organization for Standardization Standard. This is a primary recommendation for which there is an urgent international need. Other key recommendations are development of validation standards specifically for new BP technologies and online lists of accurate devices that are accessible to consumers and health professionals. Recommendations are aligned with WHO policies on medical devices and universal healthcare. Adherence to recommendations would increase the global availability of accurate BP devices and result in better diagnosis and treatment of hypertension, thus decreasing the worldwide burden from high BP.

Influence of Age on Upper Arm Cuff Blood Pressure Measurement

Blood pressure (BP) is a leading global risk factor. Increasing age is related to changes in cardiovascular physiology that could influence cuff BP measurement, but this has never been examined systematically and was the aim of this study. Cuff BP was compared with invasive aortic BP across decades of age (from 40 to 89 years) using individual-level data from 31 studies (1674 patients undergoing coronary angiography) and 22 different cuff BP devices (19 oscillometric, 1 automated auscultation, 2 mercury sphygmomanometry) from the Invasive Blood Pressure Consortium. Subjects were aged 64±11 years, and 32% female. Cuff systolic BP overestimated invasive aortic systolic BP in those aged 40 to 49 years, but with each older decade of age, there was a progressive shift toward increasing underestimation of aortic systolic BP (P<0.0001). Conversely, cuff diastolic BP overestimated invasive aortic diastolic BP, and this progressively increased with increasing age (P<0.0001). Thus, there was a progressive increase in cuff pulse pressure underestimation of invasive aortic PP with increasing decades of age (P<0.0001). These age-related trends were observed across all categories of BP control. We conclude that cuff BP as an estimate of aortic BP was substantially influenced by increasing age, thus potentially exposing older people to greater chance for misdiagnosis of the true risk related to BP.

Real-time estimation of mean arterial blood pressure based on photoplethysmography dicrotic notch and perfusion index. A pilot study

Hypotension during general anesthesia is associated with poor outcome. Continuous monitoring of mean blood pressure (MAP) during anesthesia is useful and needs to be reliable and minimally invasive. Conventional cuff measurements can lead to delays due to its discontinuous nature. It has been shown that there is a relationship between MAP and photoplethysmography (PPG) parameters like the dicrotic notch and perfusion index (PI). The objective of the study was to continuously estimate MAP from PPG. Pulse wave analysis based on PPG was implemented using either notch relative amplitude (MAP_NRA), notch absolute amplitude (MAP_NAA) or PI (MAP_PI) to estimate MAP from PPG waveform features during general anesthesia. Estimated MAP values were compared to brachial cuff MAP (MAPcuff) and to radial invasive MAP (MAPinv). Forty-six patients were analyzed for a total of 235 h. Compared to MAPcuff, mean bias and limits of agreement were 1 mmHg (- 26 to +29), - 1 mmHg (- 10 to +8) and - 3 mmHg (- 21 to +13) for MAP_NRA, MAP_NAA and MAP_PI respectively. Compared to MAPinv, mean absolute error (MAE) was 20 mmHg [10 to 39], 11 mmHg [5 to 18] and 16 mmHg [9 to 24] for MAP derived from MAP_NRA, MAP_NAA and MAP_PI respectively. When calibrated every 5 min, MAP_NAA showed a MAE of 6 mmHg [5 to 9]. MAP_NAA provides the best estimates with respect to brachial cuff MAP and invasive MAP. Regular calibration allows to reduce drift over time. Beat to beat estimation of MAP during general anesthesia from the PPG appears possible with an acceptable average error.

Lancet Commission on Hypertension group position statement on the global improvement of accuracy standards for devices that measure blood pressure

: The Lancet Commission on Hypertension identified that a key action to address the worldwide burden of high blood pressure (BP) was to improve the quality of BP measurements by using BP devices that have been validated for accuracy. Currently, there are over 3000 commercially available BP devices, but many do not have published data on accuracy testing according to established scientific standards. This problem is enabled through weak or absent regulations that allow clearance of devices for commercial use without formal validation. In addition, new BP technologies have emerged (e.g. cuffless sensors) for which there is no scientific consensus regarding BP measurement accuracy standards. Altogether, these issues contribute to the widespread availability of clinic and home BP devices with limited or uncertain accuracy, leading to inappropriate hypertension diagnosis, management and drug treatment on a global scale. The most significant problems relating to the accuracy of BP devices can be resolved by the regulatory requirement for mandatory independent validation of BP devices according to the universally-accepted International Organisation for Standardization Standard. This is a primary recommendation for which there is an urgent international need. Other key recommendations are development of validation standards specifically for new BP technologies and online lists of accurate devices that are accessible to consumers and health professionals. Recommendations are aligned with WHO policies on medical devices and universal healthcare. Adherence to recommendations would increase the global availability of accurate BP devices and result in better diagnosis and treatment of hypertension, thus decreasing the worldwide burden from high BP.