Conduit Artery Blood Flow Influences Peripheral Arterial Stiffness Response To Reactive Hyperemia

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Previous studies have shown that peripheral arterial stiffness is reduced acutely by exercise and mechanical compression. Our recent data show that reactive hyperemia also reduces peripheral arterial stiffness. We reasoned that the reduction in arterial stiffness to all these stimuli might be due to large increases in conduit artery blood flow. If that is the case, blood flow restriction might attenuate the effect of reactive hyperemia on peripheral arterial stiffness. PURPOSE: The purpose of this study was to test the hypothesis that restricting the blood flow increase to reactive hyperemia abolishes the reduction in peripheral arterial stiffness measured by pulse wave velocity (PWV). METHODS: Eight healthy young adults (4 women; 29 ± 4 years; mean ± SD) were studied. Brachial to radial PWV was measured by placing pulse tonometers simultaneously over the brachial and radial arteries of the right arm. Arterial blood pressure was monitored continuously via photoplethysmography on the middle finger of the contralateral hand. Reactive hyperemia was performed using a rapid-release cuff positioned on the right upper arm, inflated to 220 mmHg and sustained for 5 min. Measurements were made before cuff inflation and at 5, 15, and 30 min after cuff release. Subjects underwent two reactive hyperemia challenges: with unrestricted blood flow and with blood flow restriction. For the blood flow restriction protocol, gentle pressure was applied by an investigator to the brachial artery to prevent the increase in blood flow as monitored by doppler ultrasound. RESULTS: Brachial to radial PWV was similar at baseline (10.3 ± 2.2 vs. 10.5 ± 1.5 m/s) but lower 5-min post reactive hyperemia (11.5 ± 2.9 vs. 8.7 ± 1.7 m/s; p < .05) only when blood flow was unrestricted. There was a significant time x condition interaction (p < .05). Mean arterial pressure (MAP) was not significantly different (p > 0.05) across time points. CONCLUSION: The results show that reactive hyperemia produces an acute reduction in brachial to radial PWV which is abolished by restricting the increase in brachial artery blood flow. This was a local response not confounded by arterial pressure changes. The accumulation of metabolites during reactive hyperemia and subsequent reduction in arterial stiffness may have similarities with exercise hyperemia.

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