Air plethysmography: an alternative method for assessing peripheral circulatory adaptations during spaceflights

A new approach to the study of peripheral vascular hemodynamics in microgra vity was initiated by designing an alternative methodology: air plethysmogr aphy (AP). This is the only technique that enables the quantification of va scular hemodynamics from gross measurements performed on the limbs. This pa per reports a description of the device and of the measurement protocol. A comparative study showed that AP yields results that are well correlated, a lthough not in agreement, with those obtained by means of the reference met hod in the laboratory (mercury strain gauge plethysmography, MSGP; for veno us capacity, correlation coefficient r=0.8, P<0.0001, limits of agreement 0 .9ml.100 ml(-1) and 1.4 ml.100 ml(-1); for arterial flow index, correlation coefficient r=0.7, P<0.0006, limits of agreements -20.4 ml.min(-1) and 37. 2 m.-min(-1); for half-emptying time, correlation coefficient r = 0.9, P < 0.0001, limits of agreement -0.88 s and 0.77 s), and that are characterized by good reproducibility (coefficient of variation in general lower than 12 %). Preliminary findings during spaceflight, on board the Mir Space Station , yielded data that is expected to improve our knowledge of vascular decond itioning in conditions of weightlessness.