CAPILLARY BLOOD PRESSURE IN MAN. DIRECT MEASUREMENTS IN THE DIGITS OF NORMAL AND HYPERTENSIVE SUBJECTS DURING VASOCONSTRICTION AND VASODILATATION VARIOUSLY INDUCED 12

Open Access
Publisher Website
Google Scholar
Abstract
Employing the direct microinjection method, a comparison was made of the digital capillary blood pressure of normal and hypertensive subjects. Under resting conditions, the avg. capillary blood pressures in the normal subjects were: arteriolar limb, 30.6 mm. Hg; summit, 29.5 mm. Hg; venous limb, 21.9 mm. Hg: in the hypertensive patients: arteriolar limb, 35.9 mm. Hg; summit, 28.8 mm. Hg; venous limb, 22.8 mm. Hg. This qualitative and quantitative similarity of the digital capillary blood pressure in both normal and hypertensive subjects persisted during a variety of physiologic influences; neurogenic vasoconstriction, reflex vasodilatation, reactive hyperemia, and changes in skin temperature between 27[degree] C. and 35[degree] C, No correlation existed between the capillary blood pressure and the arterial blood pressure under any of these circumstances. These findings indicated that the predominant vascular resistance in the digits of hypertensive patients is precapillary, presumably arteriolar, in origin. During the physiologic vasodilating procedures of reactive hyperemia and reflex vasodilatation, the capillary blood pressure of hypertensive patients was similar to that in normal subjects. The increased vascular resistance was not released. Following locally applied histamine, the capillary blood pressure of hypertensive subjects exceeded that of normal subjects, indicating a release, at least to some extent, of the increased vascular resistance of hypertension. The above influences, which are known to alter markedly the digital blood flow, induced but small changes in the capillary blood pressure, and then equally in both groups of subjects. The homeostatic mechanism which maintains a relatively constant capillary blood pressure during wide fluctuations in digital blood flow appeared as effective in hypertensive as in normal subjects.