Trauma
Abstracts
Cosby Arnold, MD, MPH
University of Colorado Denver School of Medicine
Disclosure Relationship(s): EMF/EMRA Resident Research Grant (List your financial relationship role.): Grants/Research Support Recipient
Background: The ankle-brachial index (ABI) assesses the integrity of the lower-extremity arterial vasculature and is used to determine the need for emergent vascular imaging in trauma. However, ABI measurement using Doppler may be difficult during EMS or helicopter transport, or busy trauma bays, with high levels of ambient noise. Use of the pulse oximeter plethysmograph (POP) waveform might circumvent this limitation. We sought to test the hypothesis that the ABI measured using the POP waveform agrees with the criterion ABI measurement by Doppler.
Methods: We conducted a cross-sectional study using a convenience sample of healthy adults age 18 or older. We measured systolic blood pressures in each participant’s right arm and right leg to calculate the ABI using three different methods: (1) Doppler and manual sphygmomanometer; (2) Pulse oximeter plethysmograph waveform and manual sphygmomanometer; and (3) Automated oscillometric sphygmomanometer (Dynamap). We repeated each method three times to quantify the variability of each method. Bland-Altman (B-A) plots were used to visually examine the agreement of Doppler-measured with POP-measured ABI and, as a secondary outcome, of Doppler-measured with Dynamap-measured ABI. We calculated 95% confidence intervals for the limits of agreement of each B-A plot.Â
Results: Among 26 participants enrolled to date, median [IQR] age was 28 [22, 54] years, 10 (38%) were male, 2 (8%) Black and 22 (85%) White, median BMI was 25.6 [20.4, 37.3], and 0 were smokers. Mean (SD) ABI values for each method were Doppler 1.1 (0.09); POP 1.08 (0.08); and Dynamap 1.04 (0.05). Mean (95% CI) B-A plot differences were: Doppler- vs. POP-measured ABI, 0.02 (95% CI -0.06, +0.10); and Doppler- vs. Dynamap-measured ABI, 0.06 (95% CI -0.12, +0.23).
Conclusion: ABI measured using the pulse oximeter plethysmograph waveform has a high level of agreement with measurement by the criterion standard Doppler. Dynamap-measured ABI agrees less well with greater variability of measured difference with Doppler-measured ABI.