Plethysmography means registration of spontaneous or provoked volume changes in a segment of the body, with which it is possible to obtain information on the circulation of blood in that segment. This method has been known for a long time and has been applied by physiologists to several circulatory problems.However, the first plethysmographic instruments, water plethysmographs, presented such difficult technical problems that their use was restricted to sophisticated research in animals and only rarely in man. The water-filled plethysmograph was then replaced by the air-filled types, but these instruments also had grave technical problems.The principle of the so-called impedance plethysmography or rheography is based on electric impedance changes when a high-frequency and low-power alternating electric current passes through the body segment under investigation. This method, developed in the 1950s and designed to detect pulse waves in the limb, does not really reflect volume changes, but changes in the electrolyte content of the segment; so it cannot be compared with methods developed to measure blood flow.Decisive progress in plethysmography took place when in 1953 Whitney' introduced &dquo;mercury in rubber strain gauge plethysmography.&dquo; With this method the changes in volume are detected by measuring the circumference of the segment. The procedure was simple and could be applied to the well-known practice of conventional plethysmography.The most important principle was venous occlusion, introduced in the first years of this century by Brodie2 and then refined by Hewlett and Van Zwaluwenburg,l which allows the volume of blood flow which passes through the segment under investigation to be measured exactly and not invasively.The method was especially applied to limbs at various levels in several pathophysiologic and clinical situations,4-' and its accuracy in comparison with other methods of measuring blood flow was demonstrated.8-12In the past years this field of study has attracted much interest from physiologists and clinicians, which stimulated the research for more sophisticated and
Multitechnical non-invasive procedures were used to assess the arteriolar effects of cinnarizine and its difluoroderivative, flunarizine, in 20 normal volun teers and in 43 elderly patients with occlusive disease of the extremities due to arteriosclerosis, 22 of whom had intermittent claudication. The trial involved six separate studies of which three were double-blind cross-over, one was a 6- month open study followed by a 6-month double-blind study and two were open studies. Significant drug-related effects were obtained by venous occlusion plethysmometry, differentiated pulse plethysmometry, oscillometry, claudicom eter, postexercise arm-ankle pressure gradients and exercise tolerance measure ments, but not by light plethysmometry and skin temperature measurements. The results indicated that cinnarizine and flunarizine improved vascular disten sion and blood flow in normal volunteers, as well as in patients with occlusive disease of the extremities due to arteriosclerosis. The patients also showed increased postexercise arm-ankle pressure gradients, improved arterial pulsa tions and better exercise performance and tolerance. The drugs were devoid of effects on sympathetic reflexes, resting blood pressure and pulse rate; they were devoid of side-effects and were well tolerated also by patients treated with antihypertensives and cardiac glycosides. Flunarizine was at least as effective as its parent compound at two to three times lower dose levels.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.