The influence of the method of data analysis on the reported accuracy of automated blood pressure measuring devices

Differences in automated and manual blood pressure measurement in hospitalized psychiatric patients

Few studies have been conducted recently with noncritically ill patients evaluating commonly used automated blood pressure (BP) devices. The purpose of this study was to compare BP values obtained using a manual sphygmomanometer versus an oscillometric automated electronic BP device on an acute care psychiatry unit. A method-comparison design was used, and data were analyzed using the Bland-Altman method. Outliers were removed, resulting in 39 participants for analyses of systolic readings and 41 participants for diastolic readings. Paired t tests revealed a significant difference in manual versus automatic systolic BP readings (p < 0.05). Automated readings averaged 3.9 points higher. No significant differences in diastolic readings (p = 0.72) were found. Care must be taken in using automated or manual BP readings to make important clinical decisions. Based on these findings, a protocol was instituted in an acute care psychiatry unit indicating that BP must be measured manually for patients with medication-hold parameters for BP.

Comparison of noninvasive blood pressure measurements in patients with atrial fibrillation

BACKGROUND AND RESEARCH OBJECTIVE

Limited research is available on the accuracy of automatic blood pressure (BP) measurement devices in patients with irregular rhythms. The purpose of this study was to examine the agreement between different methods for noninvasive BP measurement in patients with atrial fibrillation.

SUBJECTS AND METHODS

In a convenience sample of hospitalized patients with atrial fibrillation, a method-comparison study design was used to examine the agreement between 2 noninvasive devices for BP measurement (manual, automated). Blood pressure was obtained sequentially, with each device following manufacturer's directions and American Heart Association guidelines for BP determination and with BP order determined by random assignment. Heart rate and rhythm were determined from a continuous electrocardiographic monitoring. Heart rate was also recorded from the automated BP device. Differences and limits of agreement between the automated and reference standard (manual) BP devices were calculated and graphed according to the Bland-Altman method. Student t test was used to test differences in BP obtained with the 2 devices, as well as heart rate differences between the electrocardiographic monitor and automated BP device. The level of significance for all tests was set at 0.05.

RESULTS

53 participants were observed. Bland-Altman analysis found a bias plus/minus precision of -0.91 +/- 11.4 mm Hg for systolic BP and 3.3 +/- 6.9 mm Hg for diastolic BP. A significant difference was found for the diastolic BP obtained with the automated device and with that of the manual device (t52 = 3.51, P = .0009) and for heart rate differences between the automated BP device and the cardiac monitor (t52 = 2.4, P = .0217).

CONCLUSION

This study confirms that in the presence of irregular cardiac rhythms, diastolic BP and heart rate cannot reliably be measured with an automated BP device.

Validation of the Oscar 2 oscillometric 24-h ambulatory blood pressure monitor according to the British Hypertension Society protocol

OBJECTIVES

Accuracy of blood pressure measuring devices is of prime importance and should be validated before devices are used clinically. We carried out an independent evaluation of the Oscar 2 oscillometric ambulatory blood pressure monitor (SunTech Medical, Model 222) according to the British Hypertension Society (BHS) Protocol.

METHODS

Validation of the Oscar 2 was carried out in accordance with Part 1 of the British Hypertension Society protocol. Having successfully completed the first three phases, in the static validation phase blood pressure measurements were made on 114 participants simultaneously by two observers blinded from each other's readings and those of the device, giving 255 data pairs for systolic and diastolic blood pressure. Readings were made using simultaneous same-arm measurement, each observer using a dual-head binaural stethoscope and a calibrated mercury sphygmomanometer. Data were recorded independently, to the nearest 2 mmHg and were checked by the supervisor who operated the device.

RESULTS

The device mean and observer means (and standard deviations) were exceptionally close across a high range of pressures, with a mean difference for the better observer of 0+/-7 mmHg and -1+/-6 mmHg for systolic and diastolic blood pressure, respectively. With 62% of all systolic blood pressure standard vs. device differences equal or less than 5 mmHg, and 70% of all similar differences for diastolic blood pressure equal to or less than 5 mmHg, the device was categorized as Grade A for systolic and diastolic blood pressure.

CONCLUSION

The Oscar 2 was graded A for both systolic and diastolic blood pressure by the British Hypertension Society protocol and can be recommended for clinical use in an adult population.

Accuracy of the Omron RX-M, an automated blood pressure measuring device, measuring blood pressure at the wrist, according to a modified British Hypertension Society protocol

OBJECTIVE

To determine the accuracy of the Omron RX-M, a device measuring blood pressure oscillometrically at the wrist.

METHODS

In 89 subjects (mean age 55+/-14 years) blood pressure measurements at the wrist with the Omron RX-M were compared to sequential blood pressure measurements with a mercury sphygmomanometer at the (same) upper-arm and to simultaneous measurements with the Omron HEM-705 CP at the opposite arm.Measurements with analyzed according to the British Hypertension Society (BHS) - protocol 1993, to the protocol of the Association for the Advancement of Medical Instrumentation (AAMI) and (retrospectively) to the new 'International Protocol'.

RESULTS

Mean differences (+/-SD) between the measurements with the mercury sphygmomanometer and the Omron RX-M were -7.5+/-8.4 mmHg for diastolic blood pressure (DBP) and -2.5+/-12.2 mmHg for systolic blood pressure (SBP), thus not fulfilling the AAMI-criteria (< or =5+/-8). According to the BHS-criteria a grade D was achieved for both DBP and SBP. Compared to the Omron HEM 705 CP results were -6.3+/-7.1 for DBP (grade D) and -4.1+/-12.7 for SBP (grade D). The Omron RX-M also failed to pass the new 'International Protocol' in phase 1.

CONCLUSION

Although easy to use, based on this study the Omron RX-M can not be recommended to determine blood pressure accurately.

Accuracy of the Welch Allyn Vital Signs Monitor 52000 automatic blood pressure measuring device according to a modified British Hypertension Society protocol

The accuracy of the Welch Allyn Vital Signs Monitor, a compact device for the oscillometric measurement of blood pressure, was determined according to the British Hypertension Society protocol. The monitor achieved a grade C for diastolic and a grade D for systolic blood pressure. The device is suitable for monitoring a patient, for example post-operatively, in the emergency department or during an intervention. The device cannot, however, be recommended for an exact determination of blood pressure when compared with the mercury sphygmomanometer. In an earlier validation report, the Welch Allyn Vital Signs Monitor achieved a grade A for both diastolic and systolic blood pressure. After adjusting for the difference in method of calculating the grades used in the two studies, there remained a considerable difference in grading results, for which no clear reason could be found.