THE MEASUREMENT OF BLOOD PRESSURE, THE CRITICAL OPENING PRESSURE, AND THE CRITICAL CLOSING PRESSURE OF DIGITAL VESSELS UNDER VARIOUS CIRCUMSTANCES

Abstract

A spectroscopic technique for the estimation of the critical opening pressure (COP) or critical closing pressure (CCP) of small vessels in the finger is described. The spectroscopic method of estimation of the systolic blood pressure, which is part of the technique and which involves the detection of reappearance of oxyhemoglobin absorption bands in the spectrum of reflected light from the skin distal to a blood pressure cuff that is slowly deflated, was compared to the auscultatory technique in 38 subjects on 53 occasions and gave the same results. The COP of small vessels in the finger estimated by the spectroscopic technique was decreased by body heating and by digital nerve block as had been previously shown by the microscopical method. The COP of vessels in the finger after digital nerve block in 43 normotensive young women between the ages of 18 and 22 years ranged from 2 to 19 mm Hg with a mean of 9.5 ± 4.6 (S.D.) mm Hg. When the COP was estimated in many of the same subjects after preparation as for measurement of the basal metabolic rate, in most cases it fell within the range of values obtained after nerve block. The COP in 26 subjects ranged from 1 to 22 mm Hg with a mean of 10.9 ± 5.0 (S.D.). The values for CCP estimated by the spectroscopic method in 81 individuals were not significantly different from those for COP estimated on the same occasion.