Flow to the forearm is measured before and after a blood pressure cuff inflated above systolic pressure is released after five minutes of occlusion. Flow immediately after cuff deflation is markedly higher than baseline and returns gradually over one minute. This phenomenon is called:

• A Active hyperemia
• B Reactive hyperemia ✓
• C Autoregulatory escape
• D Vasomotion

Explanation

Reactive hyperemia is the transient increase in organ blood flow that follows release of a temporary arterial occlusion. During occlusion, tissue accumulates vasodilator metabolites and develops an oxygen deficit, so arterioles dilate maximally; when pressure is restored, flow overshoots in proportion to the duration and severity of the blockage until the debt is repaid. Active or functional hyperemia refers to increased flow during increased metabolic activity, such as exercising muscle. Vasomotion is spontaneous rhythmic arteriolar constriction and dilation.

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

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