A COMPARISON OF PROCEDURES FOR INCREASING BLOOD FLOW TO LIMBS USING AN IMPROVED OPTICAL PLETHYSMOGRAPH

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Abstract
A boot plethysmograph is descr., the open end of which is sealed around the leg without constriction by the use of plaster of paris and Unna paste. Air conduction and optical recording with a Frank segment capsule give the system a high sensitivity with frequencies up to 100/sec. Artefacts incurred through displacement of fluid into the plethysmograph by the inflated collecting cuff are avoided by use of suitable stopcocks so that recording begins 1 sec. after cuff inflation. The rise of a full pulse beat starting exactly 1.6 sec. after inflation is used to measure the net flow per cycle from which the blood flow per min. per 100 cc of leg substance is calculated. The advantages of the apparatus are ease of application, high sensitivity, accurate representation of phasic flow, accurate minute blood flow determinations and avoidance of errors inherent in other conventional procedures. A study of the phasic flow during a single pulse cycle reveals the normal presence of arterial backflow. The importance of this observation in regard to oscillo-metric methods of blood flow measurement is demonstrated. Resting blood flow remains constant within 6% of the mean during repeated detns. It varies greatly in different individuals, or in the same individual from day to day unless strict basal conditions are observed. Direct application of heat for 30 min. at 45[degree]C and sciatic nerve block are the most efficacious procedures for promoting maximal blood flow in the leg and are equally effective. Application of heat to both upper extremities produces only one half their effect on flow in the lower extremity. No increase in blood flow followed spinal anesthesia or sacral diathermy.