The Effect of Body Position and Forelimb Exercise on Cephalic Blood Flow

Abstract

Flow through both common carotid, vertebral, and subclavian arteries was measured with "C-core" probes and square wave electromagnetic flowmeters in mongrel dogs. Exercise of the neurally isolated forelimb was simulated by electrical stimulation to obtain first clonic and then tetanic muscle contraction. Exercise was performed in the horizontal supine, 30° head-up, and 30° head-down positions. Bilateral forelimb exercise induced abrupt increase in subclavian artery flow and conductance. Cephalic arterial flow and conductance decreased at the onset of exercise and showed gradual recovery. Left subclavian artery flow and conductance decreased during right forelimb exercise. Right subclavian and brachiocephalic artery flow decreased during left forelimb exercise. Head-up position induced general decreases in cephalic blood flow in spite of increased mean arterial blood pressure. Response patterns of flow and conductance during bilateral exercise did not differ significantly from those in the horizontal supine position. Administration of gallamine triethiodide before stimulation eliminated all hemodynamic responses. Femoral artery flow and conductance decreased on the side contralateral to the side of the exercising limb. The clinical implications of redistribution of blood are discussed.