Evaluating the impact of measurement uncertainty in blood pressure measurement on hypertension diagnosis

Sphygmomanometer Dynamic Pressure Measurement Using a Condenser Microphone

There is a worldwide need to improve blood pressure (BP) measurement error in order to correctly diagnose hypertension. Cardiovascular diseases cause 17.9 million deaths annually and are a substantial monetary strain on healthcare. The current measurement uncertainty of 3 mmHg should be improved upon. Dynamic pressure measurement standards are lacking or non-existing. In this study we propose a novel method of measuring air pressure inside the sphygmomanometer tubing during BP measurement using a condenser microphone. We designed, built, and tested a system that uses a radiofrequency (RF) modulation method to convert changes in capacitance of a condenser microphone into pressure signals. We tested the RF microphone with a low-frequency (LF) sound source, BP simulator and using a piezoresistive pressure sensor as a reference. Necessary tests were conducted to assess the uncertainty budget of the system. The RF microphone prototype has a working frequency range from 0.5 Hz to 280 Hz in the pressure range from 0 to 300 mmHg. The total expanded uncertainty (k = 2, p = 95.5%) of the RF microphone was 4.32 mmHg. The proposed method could establish traceability of BP measuring devices to acoustic standards described in IEC 61094-2 and could also be used in forming dynamic BP standards.

Overview of blood pressure measurement by Brazilian health professionals

Although automated monitors for blood pressure (BP) measurement are used increasingly worldwide, understanding of how such devices are used in Brazil is low. This study analyzed the status of BP measurement by Brazilian health professionals. A questionnaire regarding experience with BP measurement was sent electronically to Brazilian nurses, nursing assistants, and doctors. It had 2004 responses. Previous experience with use of automated monitors was most frequent in men (71.2%), nursing technicians (65.5%), specialists (61.1%), secondary care (71.9%), emergency care (70.6%), or the private sector (66.3%). The least complied aspects of the standardized measurement protocol were availability of various cuff sizes (53.9% and 72.9% for auscultatory and oscillometric methods, respectively) and proper calibration checks (21.5% and 46.8% for auscultatory and oscillometric methods, respectively). Brazilian health professionals report not adequately performing all the necessary aspects to measure BP in accordance with the standardized protocol in both methods, but mainly regarding the oscillometric.

Risk factors of the progression to hypertension and characteristics of natural history during progression: A national cohort study

Background

Although the high disease burden that results from cardiovascular complications of hypertension, factors related to the progression to hypertension in the normotensive population are not actively reported. The purpose of this study was to estimate the rate of the progression to hypertension and to reveal the associated risk factors.

Methods

The study included normotensive participants from the National Health Insurance Service-National Health Screening Cohort, and contained a 10% sample of all adults who received a national health screening test in either 2002 or 2003. At the end of the study in 2015, the patients were divided into two groups based on whether or not they progressed to hypertension. Cox proportional hazard modeling was performed to identify risk factors for progression. Subgroup analysis using logistic regression was employed to reveal factors influencing the different natural history of the progression.

Results

Among the 75,335 included participants, the progression rate to hypertension was 66.39% (50,013), with an adjusted incidence rate of 8.62 per 100 person-year in the aged 40–64 group and 12.68 in the aged 65 or above group. Age, BMI, hemoglobin, and family history of hypertension and other diseases were related to the progression. Among the progression group, 78.21% (39,116) participants skipped a pre-hypertensive status; this group consisted of older females with lower pulse pressure and more alcohol consumption compared to people who had pre-hypertensive status before the progression.

Conclusion

Substantial risk factors for the progression to hypertension should be carefully managed even in normotensive participants who receive health screening tests.

Toward a Framework for Outcome-Based Analytical Performance Specifications: A Methodology Review of Indirect Methods for Evaluating the Impact of Measurement Uncertainty on Clinical Outcomes

BACKGROUND

For medical tests that have a central role in clinical decision-making, current guidelines advocate outcome-based analytical performance specifications. Given that empirical (clinical trial-style) analyses are often impractical or unfeasible in this context, the ability to set such specifications is expected to rely on indirect studies to calculate the impact of test measurement uncertainty on downstream clinical, operational, and economic outcomes. Currently, however, a lack of awareness and guidance concerning available alternative indirect methods is limiting the production of outcome-based specifications. Therefore, our aim was to review available indirect methods and present an analytical framework to inform future outcome-based performance goals.

CONTENT

A methodology review consisting of database searches and extensive citation tracking was conducted to identify studies using indirect methods to incorporate or evaluate the impact of test measurement uncertainty on downstream outcomes (including clinical accuracy, clinical utility, and/or costs). Eighty-two studies were identified, most of which evaluated the impact of imprecision and/or bias on clinical accuracy. A common analytical framework underpinning the various methods was identified, consisting of 3 key steps: (a) calculation of "true" test values; (b) calculation of measured test values (incorporating uncertainty); and (c) calculation of the impact of discrepancies between (a) and (b) on specified outcomes. A summary of the methods adopted is provided, and key considerations are discussed.

CONCLUSIONS

Various approaches are available for conducting indirect assessments to inform outcome-based performance specifications. This study provides an overview of methods and key considerations to inform future studies and research in this area.

Evaluating the performance of automated sphygmomanometers using a patient simulator

BACKGROUND AND OBJECTIVE

Automated sphygmomanometers use the oscillometric method to measure blood pressure, which is based on an algorithm that relates the amplitude of the oscillometric waveform pulses and the pressure inside the cuff. Validation uses empirical information from clinical trials conducted by each manufacturer. Consequently, measurement algorithms are not harmonized, being based on distinct arterial waveforms, according to each group of volunteers of the clinical test. In the present study, a patient simulator was used to generate standardized, consistent oscillometric waveform pulses to test the algorithms used in six sphygmomanometers.

MATERIALS AND METHODS

Six different upper arm and wrist-based automated sphygmomanometers were tested using a patient simulator comprising four different blood pressure levels, Psys/dia (mmHg): 80/50; 120/80; 150/100; 200/150. The devices were also submitted to conformity assessment. The variance of repeatable measurements was also analyzed.

RESULTS

All tested automated sphygmomanometers complied with metrological requirements, presenting results within the range of ±2 mmHg for static calibration. Systematic discrepancies, greater than 20 mmHg, were observed between sphygmomanometers' results from upper arm and wrist-based models. Differences reaching 12.8 mmHg in diastolic pressure results were observed among upper arm devices.

CONCLUSION

These results may have a clinical impact and indicate the need for a standardized algorithm, with a harmonized approach for validation. Moreover, the algorithm of the wrist-based devices is being affected by the use of the brachial artery waveform as reference for its validation, which also reveals that the current approach needs standardization, especially regarding the use of patient simulators.24299305.