Are Automated Blood Pressure Apparatus Reliable? Automated versus Manual Measurement of Blood Pressure CC09-CC12
Dr. K Senthil Kumar,
Associate Professor, Department of Physiology, Meenakshi Medical College and Research Institute, Kanchipuram, Tamil Nadu, India.
Introduction: With hypertension becoming a global burden, it is necessary to validate the Blood Pressure (BP) recordings, used to screen and follow-up patients for hypertension. Since three different devices (mercury manometer, aneroid meter, and digital) are commonly used throughout the world, a study was proposed to compare the recordings of the three devices.
Aim: To evaluate the validity of aneroid and digital BP monitors as compared to mercury manometer.
Materials and Methods: BP was measured in 240 healthy subjects of both sex (Male=127, Female=113) using mercury manometer, aneroid and digital BP monitor from the same arm consecutively with five minutes interval between each recording. The data were analysed using SPSS 21, Systolic Blood Pressure (SBP) and Diastolic Blood Pressure (DBP) readings of aneroid and digital monitors were compared with mercury manometer. British Hypertension Society (BHS) protocol, Association for the Advancement of Medical Instrumentation (AAMI) standards and Bland Altman scatter plots were used to validate the aneroid and digital BP monitors.
Results: The difference in SBP measured using mercury manometer and aneroid meter was 0.675±7.12 mmHg and mercury manometer and digital monitor was 1.65±11.08 mmHg. The difference in DBP using mercury manometer and aneroid meter was 1.75±6.3 mmHg and mercury manometer and digital was 2.76±8.8 mmHg. While aneroid meter satisfied the AAMI criteria, digital monitor did not. The BHS grade for aneroid meter was C (poor) and digital D (very poor). According to Bland-Altman plot, the bias in SBP for aneroid was minimal with 0.675 (-13.28-14.63), for digital -1.41 (-21.66-18.84) and in DBP for aneroid was 1.75 (-10.6-14.1), for digital was the highest with 2.76 (-14.47-20.01).
Conclusion: BP measured using aneroid and digital monitors varied significantly from the mercury manometer and showed higher levels of inaccuracy and hence should be used with caution in clinical setting.