Key result
Post-bed rest upright IVC collapse occurs in ~42% of subjects, tracking with narrowed pulse pressure.
Why the study?
The study aimed to evaluate the usefulness of inferior vena cava diameter measurements on abdominal echograms as an indicator of venous return changes in subjects with orthostatic intolerance induced by simulated microgravity.
Observational (n=12)
IVC diameter patterns after bed rest leave open its utility as venous return marker in orthostatic intolerance; hypothesis-generating, needs validation.
We evaluated the usefulness of measurements of the inferior vena cava (IVC) diameters on abdominal echograms as an indicator of changes of venous return in subjects with orthostatic intolerance (OI) induced by simulated microgravity. We performed a standing test and recorded the IVC diameters on abdominal echograms in 12 subjects placed on a 20-day 6 degrees head-down-tilt bed-rest experiment. We found that different patterns of changes in IVC diameter occurred in the standing test on day 10 of the experiment; in five subjects with a marginal decrease in pulse pressure, IVC diameters in the upright position were markedly decreased compared with those in the supine position. In five subjects with feelings of discomfort, the IVC diameters in the upright position distended or did not decrease from those in the supine position. These results suggested that the changes in IVC diameter on the standing test indicated the presence of various types of hemodynamic responses of OI caused by simulated microgravity. In this study, we also evaluated changes in body-water compartments by conducting multifrequency bioelectrical impedance analysis. Longitudinal data analysis showed that the total body-water-to-fat-free mass and extracellular fluid-to-fat-free mass ratios decreased during the experimental period and recovered thereafter, and that the ratio of intracellular fluid to fat-free mass decreased during the experiment. No significant difference in changes in body-water compartments was seen among subjects with different patterns of changes in IVC diameters. Measurement of IVC diameter was useful to estimate hemodynamic changes in subjects with OI.
No takes yet. Share an insight, caveat, or question.
Ishizaki et al. (2004) conducted an observational in Orthostatic intolerance induced by simulated microgravity (n=12). Abdominal echogram measurement of inferior vena cava (IVC) diameter during standing test on day 10 of 6-degree head-down-tilt bed rest vs. Supine position was evaluated on Changes in inferior vena cava (IVC) diameter from supine to upright position during standing test on day 10. Abdominal echogram IVC diameter measurement on day 10 of bed rest showed marked upright decrease in 5/12 (41.7%) subjects with lower pulse pressure and no decrease in 5/12 (41.7%) with discomfort.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: