A blood pressure cuff is inflated above systolic pressure on a volunteer's arm for five minutes and then released. Forearm blood flow measured immediately after deflation is several times the resting value and returns to baseline over about a minute. This phenomenon is called reactive hyperemia and results primarily from:

• A Accumulation of local vasodilator metabolites during the period of ischemia ✓
• B Myogenic relaxation triggered by the sudden fall in wall tension
• C Reflex sympathetic dilatation mediated through the spinal cord
• D Rebound increase in cardiac output after cuff release

Explanation

During occlusion, tissue metabolism continues while oxygen delivery stops, so adenosine, CO2, potassium and other metabolites accumulate and arteriolar smooth muscle relaxes. When the cuff is released, the reduced downstream resistance produces flow far above resting levels until metabolites are washed out. It persists in a denervated limb, proving it is locally mediated, and it also has a modest myogenic component. Cardiac output is essentially unchanged by forearm cuff release.

Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.

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