Apparatus for Measuring Relative Blood Viscosity

Abstract

A method for measuring blood viscosity which can be applied to small quantities of blood containing no anticoagulant, and which can be repeated at several minute intervals is described. The method utilized an old principle of measuring time of flow of a fixed quantity of blood (0.1 ml) through a fixed capillary tube (hypodermic needle with a bore approximating 0.3 mm), using a fixed negative pressure of 100 mm of mercury. The needle and pipette which come into contact with the blood are maintained at a temperature of 37°C±0.5°C. The blood is drawn into a 2‐ml siliconed syringe through a size 20 siliconed intravenous needle. The calibrated capillary tube is then inserted through the tip of the syringe and negative pressure applied. The time of flow is measured with a stop clock to 0.1 second. Duplicate measurements on the same sample of blood can be made in less than 30 seconds. A high vacuum pump is included with the apparatus to clean and dry the needles and calibrated pipette immediately after each measurement. The relative viscosity of the blood is then computed by dividing the time for flow of 0.1 ml of blood by the time for flow of water at the same temperatures.