Endothelial function assessment in nutritional research studies: a comparison of two arterial occlusion sites for assessing reactive hyperemia using a peripheral arterial tonometry device

Abstract

Endothelial function assessment can be an important tool in evaluating artery health in humans, and can be an important phenotyping tool in nutritional research studies as well as an early indicator of cardiovascular disease. We conducted a study of endothelial function in healthy adults using reactive hyperemia peripheral arterial tonometry (RH‐PAT) by the EndoPAT™ device (Itamar Medical Ltd., Caesarea, Israel) in order to compare two arterial occlusion sites. Brachial artery (upper arm) occlusion is the most common occlusion site, yet a forearm occlusion site may be a potentially valid site for endothelial function testing. RH‐PAT testing is an operator independent, non‐invasive technique that measures the arterial pulse wave amplitude using pneumatic fingertip probes during reactive hyperemia allowing a RH‐PAT index (RHI) to be calculated. Reactive hyperemia was achieved by occluding either the upper arm (brachial artery) or the forearm (ulnar and radial arteries) in the individual using a blood pressure cuff inflated to ~200 mmHg for 5 minutes. Twenty healthy adults (14 female, 6 male), age 38 ± 12 years (mean ± SD) and BMI 24 ± 3 kg/m2 participated in the study. RH‐PAT measurements were determined in the morning after a 12 hour fast. Participants were tested approximately 3 days apart using a crossover design with randomization of upper arm and forearm as occlusion sites. The participant's non‐dominant arm was always the occluded arm. Participants were tested in a quiet, temperature‐controlled (21–24°C) room in a supine position for at least 15 minutes prior to the 15 minute test: 5 minute baseline, 5 minute occlusion, and 5 minute post‐occlusion. A self‐reported numeric pain intensity scale (0–10) was used to evaluate pain during the occlusion and post‐occlusion (hyperemic period) portion of the measurement. The RHI is the post‐to‐pre occlusion PAT signal ratio in the occluded arm, relative to the same ratio in the control arm, corrected for baseline vascular tone of the occluded arm. The mean RHI for the two occlusion sites: 2.15 ± 0.78 (upper arm) and 2.36 ± 0.75 (forearm) was not different (p=0.18, paired t‐test). A Pearson correlation of the RHI from both sites (r=0.602, p=0.005) was positive and significant. The mean reported pain intensity for the upper arm was 3.7 ± 1.3 compared to 2.7 ± 1.8 for the forearm; these indices were significantly different (p=0.002, signed‐rank test). In summary, occlusion of the forearm appears to be a potentially valid alternate occlusion site for RH‐PAT measurement and is less painful than using the upper arm as an occlusion site. In addition, the occlusion site should be standardized in the study protocol. Human study approved by the UC Davis Institutional Review Board.Support or Funding InformationUSDA, ARS Projects: 2032‐51000‐022; 203253000‐001