Abstract:
Objective: To determine the comparability between the systolic blood pressures as measured on the left upper arm and left forearm in Adult Emergency Department patients (the AEDBP trial) with a view to determining the clinical acceptability of use. Design: A single centre, prospective, cross-over randomised trial was conducted over six weeks; commencing May 10th 2011. Setting: Adult Emergency Department, Auckland City Hospital. Participants: 44 participants who met inclusion / exclusion criteria. Primary Outcome Measure: To assess agreement between the systolic blood pressures as measured on the left upper arm and forearm. Secondary Outcomes: Explore the relationship of blood pressure differences with participant characteristics of age, sex, ethnicity, smoking history, and obesity. Results: Using Bland-Altman method for statistical analysis, the primary outcome for systolic blood pressure showed a mean difference of-2.2 mmHg (95% C.I. -5.2, 0.7), with the 95% limits of agreement calculated at 16.8 mmHg and -21.2 mmHg; providing a range of ±19 mmHg. There was less variability in mean differences between the two sites of measure when the participants systolic blood pressure was 100 mmHg - 140 mmHg compared to >140 mmHg (p = 0.002). Blood pressure disparity was not associated with participant characteristics. Conclusions: The limits of agreement between the upper arm and forearm sites were outside the a priori (±10 mmHg) specified for clinical agreement. However, there was good agreement between sites when the systolic pressure was 100 – 100 mmHg. Clinically, the findings preclude the routine use of the forearm as a site for blood pressure measurement. In Emergency Department treatment decisions are contingent upon the clinical presentation in conjunction with blood pressures, other vital signs, and their subsequent trends alongside other pertinent diagnostics. Blood pressure measures are not used in isolation and inaccuracies in measurements may be mitigated by other factors. Therefore, disparities of ± 19 mmHg between the sites may be acceptable for clinical purposes. Further exploration to quantify the definition of a clinically acceptable level of agreement for the acute population would be beneficial.
