NEW OSCILLOMETRIC METHOD FOR INDIRECT MEASUREMENT OF SYSTOLIC AND MEAN ARTERIAL-PRESSURE IN THE HUMAN FINGER .1. MODEL EXPERIMENT

To analyze the mechanism of the occurrence of the maximum volume pulsation in an artery during the application of counterpressure, the static and dynamic pressure-volume (P-V) relationship was measured in excised arterial segments placed in a compression chamber. The volume change caused by perfusing the segment with a sinusoidal pump was detected by an infrared photoelectric plethysmograph during the application of counterpressure. The characteristc change in the amplitude of volume pulsation in response to the gradual change in the counterpressure was due to the nonlinearity of the P-V relation of the artery, and the value of the counterpressure showing the maximum pulsation amplitude coincided with the mean arterial pressure. It was concluded that the maximum volume pulsation occurs when the transmural pressure is equal to zero, i. e. , the arterial wall is unloaded. Based on the results a new oscillometric method for the indirect measurement of systoloc and mean arterial pressure in an arterial segment was designed. By comparison of data with the actual pressure produced by perfusing the segment, it was demonstrated that systolic and mean arterial pressure can be indirectly measured by this technique within plus or minus 3 mm Hg error.