Evaluation of blood pressure measuring devices

Thin, soft, wearable system for continuous wireless monitoring of artery blood pressure

Continuous monitoring of arterial blood pressure (BP) outside of a clinical setting is crucial for preventing and diagnosing hypertension related diseases. However, current continuous BP monitoring instruments suffer from either bulky systems or poor user-device interfacial performance, hampering their applications in continuous BP monitoring. Here, we report a thin, soft, miniaturized system (TSMS) that combines a conformal piezoelectric sensor array, an active pressure adaptation unit, a signal processing module, and an advanced machine learning method, to allow real wearable, continuous wireless monitoring of ambulatory artery BP. By optimizing the materials selection, control/sampling strategy, and system integration, the TSMS exhibits improved interfacial performance while maintaining Grade A level measurement accuracy. Initial trials on 87 volunteers and clinical tracking of two hypertension individuals prove the capability of the TSMS as a reliable BP measurement product, and its feasibility and practical usability in precise BP control and personalized diagnosis schemes development.

Impact of age on the association between 24-h ambulatory blood pressure measurements and target organ damage

OBJECTIVE

The aim of this study was to evaluate the impact of age on the associations between hemodynamic components derived from 24-h ambulatory blood pressure (24-h ABPM) and target organ damage, in apparently healthy, nonmedicated individuals.

METHODS

Twenty-four-hour ABPM and target organ damage (left ventricular mass index, pulse wave velocity, urine albumin : creatinine ratio and carotid atherosclerotic plaques) were evaluated in 1408 individuals. Associations were examined in regression models, stratified for age [middle-aged (41 or 51 years) or elderly (61 or 71 years)], and adjusted for sex, smoking status, and total-cholesterol.

RESULTS

In middle-aged individuals, an increase of 10 mmHg in 24-h SBP was independently associated with an increase of 3.8 (2.7-4.8) g/m in LVMI. The effect was nearly doubled in the elderly subgroup, where the same increase resulted in an increase in LVMI of 6.3 (5.0-7.6) g/m (P for interaction <0.01). An increase of 10 mmHg of 24-h SBP was associated with a 6.7% increase in pulse wave velocity in middle-aged individuals and with an 9.1% increase in elderly individuals (P for interaction <0.01). An independent association between 24-h ABPM and urine albumin : creatinine ratio was only observed in the elderly subgroup. Associations between the presence of atherosclerotic plaques and components from 24-h ABPM except 24-h DBP were not modified by age (all P for interaction >0.26).

CONCLUSION

Age enhances the associations between hemodynamic components obtained from 24-h ABPM and measures of arterial stiffness, microvascular damage, and cardiac structure, but not atherosclerosis.

Validation of a noninvasive blood pressure monitoring device in normotensive and hypertensive pediatric intensive care patients

OBJECTIVE

To evaluate the performance and to define limitations of a noninvasive blood pressure monitoring device in the critically ill pediatric population.

METHOD

Patients were included in the study if they were admitted to the Pediatric Intensive Care Unit, were between the ages of 1 month and 18 years with wrist circumferences of > or =10 cm, and had an indwelling arterial line. Patients were excluded if their systolic blood pressure differed by > or =7.5% between their upper extremities. The measurements were collected simultaneously with those from an arterial line by a computer interfaced with the noninvasive blood pressure monitoring system and the patient's monitor. Heart rates were calculated from the recorded pulse waveforms of the arterial lines. Comparison analyses were performed via bias and precision plots of the blood pressure and heart rate data in addition to calculation of Pearson's correlation coefficients and concordance correlation coefficients. As a nonparametric method of comparison, the proportion of measurements that differed by greater than 10% was calculated. Results. Blood pressures and heart rates of 20 patients between the ages of 12 months and 17 years were monitored by a noninvasive blood pressure monitor for 30 min per patient. This data collection resulted in 2015 data points for each blood pressure and heart rate for comparison of methods. Concordance correlation coefficients were the following: systolic blood pressure, 0.93; diastolic blood pressure, 0.93; mean blood pressure, 0.94; and heart rate, 0.85.

CONCLUSIONS

The noninvasive blood pressure monitor is capable of producing an accurate blood pressure measurement every 12-15 heartbeats in addition to providing a pulse waveform and digital display of the heart rate. Our study showed good agreement between the methods in the normotensive and hypertensive critically ill pediatric population with a wrist circumference limitation defined at > or =11 cm.

Wrist blood pressure-measuring devices: a comparative study of accuracy with a standard auscultatory method using a mercury manometer

BACKGROUND

In this study, we compared two wrist blood pressure-measuring devices, the Omron RX and the Nissei WS-310, against a mercury manometer.

METHOD

A total of 152 subjects attending an out-patient hypertensive clinic were recruited from a randomized blood pressure survey, 87 patients (mean 44.4 +/- 14.5 years of age) being selected according to the Association for the Advancement of Medical Instrumentation/British Hypertension Society standards. Device validation was assessed through the use of sequential same-arm readings compared with readings taken using a mercury sphygmomanometer by the two trained observers.

RESULTS

There were no differences between the observers and the monitors for diastolic readings (2.8 +/- 4.8 mmHg for the Omron and 4.2 +/- 6.4 mmHg for the Nissei) according to the Association for the Advancement of Medical Instrumentation standards. The largest standard deviations -- 8.3 mmHg for the Omron and 8.8 mmHg for the Nissei, respectively -- were seen for systolic readings recorded by the observers and the monitors. According to the British Hypertension Society standards, the Omron achieved an A grade for diastolic readings and a B grade for systolic readings within 5 and 10 mmHg. The Nissei monitor achieved an A grade for diastolic readings and a B grade for systolic readings within 5 and 10 mmHg.

CONCLUSION

Patients found the wrist oscillometric devices that we tested to be comfortable and easy to use. These devices are appropriate for measuring diastolic blood pressure according to the standards, but the reliability of both devices decreased when measuring systolic blood pressure.

Comparison of the oscillometric blood pressure monitor (BPM-100(Beta) ) with the auscultatory mercury sphygmomanometer

BACKGROUND

To compare directly the accuracy of the BPM-100(Beta) monitor (an automated oscillometric blood pressure device) with standard auscultatory mercury sphygmomanometry.

DESIGN

The BPM-100(Beta) was connected in parallel via a T-tube to a mercury sphygmomanometer. The BPM-100(Beta) and two trained observers (blinded from each other and from the BPM-100(Beta)) measured the sitting blood pressure simultaneously.

METHODS

Means, standard deviations and ranges were calculated for all the demographic data: age, arm size, heart rate and blood pressure. The agreement between the BPM-100(Beta) and the mean of two observers (the reference) was determined and expressed as the mean +/- SD, as well as the percentage of differences falling within 5, 10 and 15 mmHg.

RESULTS

Of the 92 subjects recruited, 85 (92.4%) met the inclusion criteria, and 391 sets of sitting blood pressure and heart rate measurements were available for analysis. The mean difference between the BPM-100(Beta) monitor and the reference was -0.62 +/- 6.96 mmHg for systolic blood pressure, -1.48 +/- 4.80 mmHg for diastolic blood pressure and 0.14 +/- 1.86 beats/min for heart rate. The only limitation of the device was its tendency to underestimate higher systolic blood pressures. This problem has been addressed by a minor change in the algorithm (see the companion publication, Blood Press Monit, 6, 161-165, 2001).

CONCLUSION

The BPM-100(Beta) is an accurate blood pressure monitor for the office setting, meeting all requirements of the Association for the Advancement of Medical Instrumentation and achieving an 'A' grade according to the British Hypertension Society protocol.

Validation of a new algorithm for the BPM-100 electronic oscillometric office blood pressure monitor

BACKGROUND

To test the accuracy of a new algorithm for the BPM-100, an automated oscillometric blood pressure (BP) monitor, using stored data from an independently conducted validation trial comparing the BPM-100(Beta) with a mercury sphygmomanometer.

DESIGN

Raw pulse wave and cuff pressure data were stored electronically using embedded software in the BPM-100(Beta), during the validation trial. The 391 sets of measurements were separated objectively into two subsets. A subset of 136 measurements was used to develop a new algorithm to enhance the accuracy of the device when reading higher systolic pressures. The larger subset of 255 measurements (three readings for 85 subjects) was used as test data to validate the accuracy of the new algorithm.

METHODS

Differences between the new algorithm BPM-100 and the reference (mean of two observers) were determined and expressed as the mean difference +/- SD, plus the percentage of measurements within 5, 10, and 15 mmHg.

RESULTS

The mean difference between the BPM-100 and reference systolic BP was -0.16 +/- 5.13 mmHg, with 73.7% < or = 5 mmHg, 94.9% < or = 10 mmHg and 98.8% < or = 15 mmHg. The mean difference between the BPM-100 and reference diastolic BP was -1.41 +/- 4.67 mmHg, with 78.4% < or = 5 mmHg, 92.5% < or = 10 mmHg, and 99.2% < or = 15 mmHg. These data improve upon that of the BPM-100(Beta) and pass the AAMI standard, and 'A' grade BHS protocol.

CONCLUSION

This study illustrates a new method for developing and testing a change in an algorithm for an oscillometric BP monitor utilizing collected and stored electronic data and demonstrates that the new algorithm meets the AAMI standard and BHS protocol.

Ambulatory blood pressure in pregnancy: comparison of the Spacelabs 90207 and Accutracker II monitors with intraarterial recordings

OBJECTIVE

Our purpose was to compare systolic and diastolic blood pressures obtained with the Spacelabs 90207 (Spacelabs Medical Products, Dee Why, Australia) or Accutracker II (Suntech Medical Instruments, Melbourne, Australia) ambulatory blood pressure monitoring devices with intraarterial blood pressures in pregnant women.

STUDY DESIGN

Direct (intraarterial) and resting blood pressures with the ambulatory blood pressure monitoring device were compared in 39 pregnant women (14 Accutracker II and 25 Spacelabs 90207).

RESULTS

The Accutracker II device underestimated direct systolic pressure by -9 (-13, -3) mm Hg (median, interquartile range) (p = 0.028) but gave similar diastolic pressure. The Spacelabs 90207 device gave similar systolic pressures but overestimated direct diastolic pressure by 7 (2, 12) mm Hg (p < 0.001). Variability for systolic and diastolic blood pressures within subjects was similar with the two devices. Both received poor gradings by standards of the British Hypertension Society and did not meet criteria of the Association for the Advancement of Medical Instrumentation, with intraarterial recordings used as the reference.

CONCLUSIONS

The Accutracker II device significantly underestimated resting direct systolic pressure, whereas the Spacelabs 90207 device significantly overestimated resting direct diastolic pressure in pregnant women. Although poor gradings were achieved for both devices when intraarterial pressures were used as the reference, this is similar to comparisons of routine mercury sphygmomanometry with intraarterial recordings and does not mean these devices are unsuitable for use in pregnancy.