Comparing Circadian Rhythms in Blood Pressure Computed from the Arterial Line and Sphygmomanometer in the ICU
Finnegan E., Villarroel M., Davidson S., Harford M., Jorge J., Tarassenko L.
It has previously been shown that there is an underlying bias in blood pressure (BP) measurements between the arterial line and the sphygmomanometer cuffs. It is unclear the extent to which this bias can lead to differences in the standard of care inside the Intensive Care Unit (ICU). The objective of this study was to compare the circadian patterns of systolic, mean arterial and diastolic BP (SBP, MAP and DBP) derived from simultaneous measurements of arterial lines and sphygmomanometer cuffs in the ICU. 2,243 patients were selected from the MIMIC-III database, resulting in 22,743 data-points of paired BP measurements from the arterial line and sphygmomanometer cuff. A significant bias between the two measurement sources was found for SBP and MAP but not for DBP. In addition, a significant proportion (SBP - 51%, DBP - 23%, MAP - 41%) of cuff measurements had a difference greater than 10 mmHg with respect to the arterial line. Despite these errors, the circadian rhythms between the two signals showed a high correlation: SBP - r = 0.92 p < 0.001; MAP - r = 0.90 p < 0.001; DBP - r = 0.86 p < 0.001. Despite significant errors and bias between the arterial line and cuff, the sphygmomanometer cuff is sufficiently accurate to track circadian rhythms in BP in the ICU.