Sphygmomanometric Blood Pressure Drop on Consecutive Measurements: The Search for a Cause

This study was inspired by our oft-noted observation that the first sphygmomanometric reading of blood pressure (BP) is invariably higher than the subsequent ones recorded immediately thereafter. The objectives of this study were to establish the statistical validity of this observation and further, to probe the possible causes of the same. The sphygmomanometric BP was recorded in 30 non-obese young adults using two different protocols. In protocol-1, BP in the left arm was repeated thrice in quick succession, both in standing and supine postures. In protocol-2, BP was recorded in the supine position six times in quick succession, thrice in the left arm and immediately thereafter, thrice in the right arm. Data was compiled and analysed using appropriate statistical tests. In protocol-1, a statistically-significant drop in the blood pressure was consistently noted between quickly consecutive measurements in both standing and supine postures. Importantly, this pressure drop was not significantly affected by posture. In protocol-2, significant pressure drop was recordable from both arms. These findings rule out baroreflex as a cause of the pressure-drop on consecutive measurements and suggest a likely role of tissue compaction in the same.