[Measurement of arterial flow in the limbs: plethysmography, isotopes, electromagnetic methods]

Measurement of arterial flow is a very old practice, and intra-arterial recordings of pressure and flow have long served as a reference for experimental studies (fig. 1). The definition of a hemodynamic state is inconceivable unless these two parameters are associated. The electromagnetic method using an intra-arterial sensor measures pulsatile flow. Now, technological advances have led to the appearance of other methods providing measurement of mean (plethysmography) and nonpulsatile flow. As a result, there has been considerable confusion between mean arterial and pulsatile arterial flow (Fig. 2). Various studies have emphasized the physiological importance of pulsatile arterial flow and thus the interest in measuring it. The recording of mean flow has often proved disappointing because values are comparable in groups of normal subjects and those with arterial disease. Mean arterial flow can be measured by isotopic methods and plethysmography. Xenon-133 clearance is the isotopic method most often used. Since determination of microcirculatory flow at rest proved of no use, it was necessary to add a hyperemia test reactive to ischemia to differentiate patients with artery disease from normal subjects. Methods involving technetium and thallium have been little used since they require the presence of a nuclear medicine center and are not easily reproducible. There are numerous plethysmographic methods, but only those are studied here which allow measurement of arterial flow. Plethysmography by venous occlusion measures arterial flow by recording the increase in limb volume. The sensor is a mercury strain gauge.(ABSTRACT TRUNCATED AT 250 WORDS)