SIMULATION OF MICROGRAVITY LONG-TERM EFFECTS ON BLOOD-FORMING ORGANS

摘要

The purpose of this work is to analyse and simulate long-term effects of microgravity on blood-forming human organs. We focus our study in the effects of the absence of microgravity on the cardiovascular system. Acute effects are well established and studied and a number of countermeasures have been developed. Long-term effects have also been reported although less data has been published up to today. A physical model based on the physiological changes on cardiovascular system due to exposure to microgravity has been developed. Later modules including changes in blood forming organs such as spleen have been added and the overall system has been simulated using standard simulation tools widely available. A first number of trials were conducted in the simulation process, with standard gravity, to assess the reliability of the system. We later used the gravity factor as a parameter of the system including 1/3, 1/6, 1/100, 1/1000, 1 μg and zero-g, in order to get a wide range of results. All simulations show an acute response when applying the new value of gravity to the system. However, significant differences with the control one-g simulation after more than four days of simulated exposure time to microgravity do not upper until gravity is less than 23% (p<0.05). We were interested in those cases that these changes may provoke significant alterations in blood-forming organs. We performed a second run of simulations with later addition of modules to the system including these organs. Modelling of this modules was based on well-established clinical probabilities of developing a malfunction on the hematopoyetic function. Results show that our model of spleen was clinically affected up to a risk greater than 1%, only after more than 78.5 days exposure to gravity less than 1 ug (p<0.05) and 93 days with less than 1/1000 (p<0.05). Exposure to g-jitter was included in a third series of simulations, showing no significant results (p<0.05), when applying a g-jitter of 1 s to 5s of g from 1 μg to 10g. We conclude that according to this model, microgravity may seriously affect the hematopoyetic function of some blood-forming organs. In-flight studies should be conducted in order to validate this model and later investigate the effect of radiation and other variables. These simulations have proved successful to first evaluate the probability of developing a serious disease on orbit with the available data.