Does the Hawksley random zero sphygmomanometer underestimate blood pressure, and by how much?

Area of Science:

• Cardiovascular diagnostics
• Medical device evaluation

Background:

• Accurate blood pressure measurement is crucial for diagnosing and managing hypertension.
• Mercury sphygmomanometers have been the gold standard, but concerns about environmental toxicity have led to the development of alternatives.
• The Hawksley random-zero sphygmomanometer is one such alternative device.

Purpose of the Study:

• To compare the accuracy of blood pressure (BP) measurements obtained using the Hawksley random-zero sphygmomanometer against the standard mercury sphygmomanometer.
• To assess the consistency of any observed differences across a range of BP levels.

Main Methods:

• Simultaneous, 'blind' BP measurements were taken using both the Hawksley random-zero and mercury sphygmomanometers.
• A Y-connector linked the devices to a single cuff for concurrent readings.
• Sixty-five healthy volunteers and patients aged 20-50 years participated, with BP measurements taken in general practice and office settings.
• Data from this study were combined with six other published reports for a meta-analysis.

Main Results:

• The Hawksley random-zero sphygmomanometer showed lower mean BP readings than the mercury sphygmomanometer.
• Systolic BP (SBP) was underestimated by 1.3 mm Hg (95% CI 0.9-1.8) and diastolic BP (DBP) by 1.7 mm Hg (95% CI 1.1-2.3).
• These differences were consistent across various BP levels. Meta-analysis of nine studies indicated SBP underestimation of 1.35 mm Hg and DBP underestimation of 1.97 mm Hg (excluding outliers).

Conclusions:

• The Hawksley random-zero sphygmomanometer demonstrates a small but consistent underestimation of both systolic and diastolic blood pressure compared to the mercury sphygmomanometer.
• The findings suggest the device is reliable across a wide range of blood pressure levels.
• This information is vital for clinicians when interpreting BP readings from this device.