Capillary blood pressure in man. Direct measurements in the digits of patients with Raynaud's disease and scleroderma before and after sympathectomy

Abstract

1. 1. During vasospastic circulatory arrest, induced in the fingers by cold, (a) digital capillary blood pressure varied between 7.0 and 12.5 mm. Hg (average, 9.7 mm. Hg); (b) digital capillary blood pressure rose slowly in response to induced increases in venous pressure, but fell promptly when the increased venous pressure was suddenly lowered; (c) cessation of blood flow through the capillaries was caused by closure of vessels proximal to them. The capillaries, venules, and veins remained patent. 2. 2. Erythrocytes in clumps or loose aggregations may be isolated outside the central capillary blood stream when the digital circulation returns after a period of vasospastic circulatory arrest. Localized constriction of the capillary, or stickiness of the capillary endothelium, or both, may account for this. 3. 3. In fingers with intact innervation the average digital capillary blood pressure was as follows: arteriolar limb, 18.5 mm. Hg; summit, 22.4 mm. Hg; and venous limb, 19 mm. Hg. The gradient of fall of pressure through the capillary was small, usually less than 3 mm. Hg. 4. 4. In fingers deprived of sympathetic innervation the average digital capillary blood pressure was as follows: arteriolar limb, 27.8 mm. Hg; summit, 25.2 mm. Hg; and venous limb, 21.6 mm. Hg. The somewhat greater capillary pressure in the arteriolar limb suggests release of arteriolar tone. The gradient of pressure in the capillary is still small (6 to 7 mm. Hg).