PRINCIPAL INVESTIGATOR (S ): Robert L. Johnson, G. Wyckliffe Hoffler, Arnauld 



E. Nicogossian, Stuart A. Bergman, and Margaret M. 

 Jackson 



EXPERIMENT TITLE/NUMBER : Lower Body Negative Pressure, M092 



PROGRAM/MISSION : Skylab 2, 3, *• 



CLASSIFICATION : Human 



DISCIPLINE(S) : Cardiovascular 



OBJECTIVES : To determine the extent and time course of changes in orthostatic 

 tolerance during the weightlessness of space flight and to determine whether 

 inflight data from the experiment would be useful in predicting postflight 

 status of orthostatic tolerance. 



PROTOCOL : Basic measurements during all pref light, inflight, and postflight 

 testing included blood pressure at 30-second intervals from an automatic 

 system which detected and analyzed Korotkoff sounds, heart rate monitored 

 continuously from one component of a Frank lead vectorcardiogram, and 

 percentage change in calf volume monitored continously from capacitive 

 plethysmographic bands encircling the legs. Prior to LBNP tests, lower limb 

 volume was estimated from girth measurements taken at 3 cm intervals between 

 ankles and upper thighs . 



EQUIPMENT : Lower Body Negative Pressure device. 



RESULTS : At rest, inflight mean resting heart rates, systolic blood 

 pressures, and pulse pressures were typically increased while diastolic and 

 mean arterial pressures decreased compared to preflight values. Differences 

 in inflight responses to LBNP stress from preflight responses included greater 

 heart rate and leg volume increases in all crewmen and, in most, higher 

 diastolic pressures and mean arterial pressures and lower systolic blood 

 pressures and pulse pressures. 



CONCLUSIONS : Inflight data confirmed that lower body negative pressure in 

 weightlessness imposed a greater stress upon the cardiovascular system than in 

 Earth's gravity. Changed relationships in the anatomical distribution of 

 blood volume and extravascular fluids, altered patterns of blood flow, and 

 reduced total circulating blood volume induced by the weightless environment 

 are offered as partial explanations for the changes. The exaggerated inflight 

 responses to lower body negative pressure generally appeared to decline after 

 the first 30-50 days of flight. Inflight data served as a fairly accurate 

 prediction of the initial postflight status of orthostatic tolerance. 



PUBLICATIONS : 26, 27, 42, 211, 298, 299, 300, 301, 329, 576 



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