CAPILLARY BLOOD PRESSURE IN MAN. COMPARISON OF DIRECT AND INDIRECT METHODS OF MEASUREMENT. 1

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Abstract
The indirect, pressure capsule method of Danzer and Hooker and the direct, microinjection method of Landis were critically analyzed with the purpose of determining the accuracy of each in recording capillary blood pressure and its changes. The capillaries of the nail fold of man were studied under normal conditions and when the intra-capillary pressure was altered. Increases in capillary blood pressure were produced chiefly by raising the venous pressure in the hand to varying levels below diastolic arterial pressure. In 31 different capillaries in 18 subjects the direct method recorded capillary blood pressures which changed with alterations in venous pressure and which always exceeded venous pressure. The capillary pressure obtained by the indirect method in over 200 capillaries remained relatively fixed and failed to show any correlation with venous pressure. It is evident that only the direct method gives accurate readings of capillary pressure.