Ultrasound-Guided Radial Artery Compression to Assess Blood Pressure

We proposed using compression sonography to observe the coaptation and collapse of the radial artery as a surrogate for automated cuff blood pressures (BP). We hypothesize that the pressure required to achieve coaptation and complete collapse of the artery would correlate to the diastolic and systolic BP, respectively. This pilot study was to assess the feasibility of ultrasound-guided radial artery compression (URAC) for BP measurement and compare patient comfort levels during automated cuff with URAC measurements.

This was a prospective cohort pilot study with a convenience sampling of 25 adult patients at a single urban emergency department. URAC pressure was measured, followed by cuff manometry on the same arm. A 100mL normal saline bag was connected to the Stryker pressure monitor and placed on the volar wrist. Pressure was applied to the bag with a linear transducer and the radial artery was observed for coaptation of the anterior and posterior walls and complete collapse. Pressures required for coaptation and collapse were recorded from the Stryker display. Patient level of comfort was also documented during the URAC method, with patients reporting either "more," "same" or "less" comfort in comparison to automated cuffs. We analyzed data using intraclass correlation and paired t-tests. Interrater reliability was calculated using intraclass correlation.

The mean cuff systolic BP was 138.6 ± 22.1 mmHg compared to 126.9 ± 19.8 mmHg for the URAC systolic BP (p=0.02). For diastolic BP, there was no significant difference between the cuff BP and the URAC BP (83.7 ± 13.0 cuff vs. 86.5 ± 19.8 URAC, p=0.46). The intraclass correlation (ICC) for systolic BP was 0.48 (p=0.04) and 0.57 (p=0.02) for diastolic BP. The agreement between the two observers was 0.88 for identifying coaptation on ultrasound (diastolic pressure) and was 0.92 for identifying collapse (systolic pressure). Eighty percent (20/25) of subjects found the URAC method more comfortable than the cuff measurement, and the remainder found it the same (5/20).

This pilot study showed statistically significant moderate correlation between automated cuff diastolic BP and URAC measurements for vessel coaptation. Additionally, most patients found the URAC method more comfortable than traditional cuff measurements. Compression ultrasonography shows promise as an alternative method of BP measurement, though future studies are needed.