Plethysmography with optoelectronic sensors: comparison with mercury strain gauge plethysmography

The study and follow-up of certain physiological adaptations in microgravity, particularly vascular and venous ones, require the use of reliable equipment that yields results well correlated with data provided by equipment usually used in clinical examinations. The purpose of the present study was to evaluate the reproducibility of results obtained using a new type of plethysmography, plethysmography with optoelectronic sensors or volometry, and to verify whether these results correlate with those yielded by mercury strain gauge plethysmography. The plethysmograph is a device which permits measuring limb volume by means of an infra-red light transmitter-receiver system that calculates cross-sectional areas at 220 successive points of a given limb segment. Calf venous capacity (calf volume measured after 50 mm Hg venous occlusion in the thigh) was measured on 27 subjects using volometry and mercury strain gauge plethysmography used as reference method. Results showed a good correlation (r = 0.8, p < 0.001) and a statistically identical reproducibility between the two methods even though venous capacity measurements obtained using these two techniques were not superimposable because they did not use the same model for limb volume measurements. Volometry therefore appears to be a technique of interest for the future, to monitor vascular and muscular physiological parameters in astronauts during long-term microgravity exposure.