tailieunhanh - Báo cáo y học: "Theoretical analysis of the mechanisms of a gender differentiation in the propensity for orthostatic intolerance after spaceflight"

Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học quốc tế cung cấp cho các bạn kiến thức về ngành y đề tài: Theoretical analysis of the mechanisms of a gender differentiation in the propensity for orthostatic intolerance after spaceflight. | Summers et al. Theoretical Biology and Medical Modelling 2010 7 8 http content 7 1 8 THEORETICAL BIOLOGY AND MEDICAL MODELLING RESEARCH Open Access Theoretical analysis of the mechanisms of a gender differentiation in the propensity for orthostatic intolerance after spaceflight 1 2 3 1 Richard L Summers Steven Platts Jerry G Myers Thomas G Coleman Correspondence rsummers@ department of Emergency Medicine University of Mississippi Medical Center Jackson Mississippi 39216 USA 2 BioMed Central Abstract Background A tendency to develop reentry orthostasis after a prolonged exposure to microgravity is a common problem among astronauts. The problem is 5 times more prevalent in female astronauts as compared to their male counterparts. The mechanisms responsible for this gender differentiation are poorly understood despite many detailed and complex investigations directed toward an analysis of the physiologic control systems involved. Methods In this study a series of computer simulation studies using a mathematical model of cardiovascular functioning were performed to examine the proposed hypothesis that this phenomenon could be explained by basic physical forces acting through the simple common anatomic differences between men and women. In the computer simulations the circulatory components and hydrostatic gradients of the model were allowed to adapt to the physical constraints of microgravity. After a simulated period of one month the model was returned to the conditions of earth s gravity and the standard postflight tilt test protocol was performed while the model output depicting the typical vital signs was monitored. Conclusions The analysis demonstrated that a 15 lowering of the longitudinal center of gravity in the anatomic structure of the model was all that was necessary to prevent the physiologic compensatory mechanisms from overcoming the propensity for reentry orthostasis leading to syncope. Background The microgravity environment .