Cerebral perfusion during acceleration stress: Phase III

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Authors
  1. Walsh, C.
  2. Cirovic, S.
  3. Samin, A.
Corporate Authors
Defence and Civil Inst of Environmental Medicine, Downsview ONT (CAN);Ryerson Polytechnic Univ, Toronto ONT (CAN) Dept of Mechanical Engineering
Abstract
The accelerations experienced in aerial combat can disrupt cardiovascular function causing visual and cognitive effects or loss of consciousness (GLOC). This report describes developments in quantitative experimental and computer models for human cardiovascular response to orthostatic stress. The goals are to understand the mechanisms of GLOC, and ot assist in the design and testing of advanced aircrew life support systems. Our earlier experimental and computational work suggested that vein mechanics control cerebal perfusion. During unprotected +Gz cardiac output is reduced by head-to-foot blood volume shifts that depend on the pressure volume relations for each of the veins. For high +Gz the internal jugular collapses, giving a high resistance that reduces cerebal flow even if G-protection maintains cardiac output. In our closed loop simulation of the response to passive head-up tilt, the arterial baroreflex model gave plausible blood pressure predicitons, but non-physiological heart rate response. Furthermore, the simulation proved inefficient furing jugular collapse. The work reported here comprises 5 main components: - An in vivo study of the internal jugular vein using doppler imaging. - An in vivo study of the human vagal arterial baroreflex. - A review of cardiac transplant recipient response to orthostatic stress. - Implementation of a cardiopulmonary reflex suggested by that review. - Improvement in simulation efficiency. TRUNCATED
Keywords
G-Induced Loss of Consciousness;G-LOC;Cerebral perfusion;Orthostatic stress;+Gz;Internal jugular vein;In vivo;Baroflex
Report Number
DCIEM-CR-2001-139 — Contractor Report
Date of publication
01 Mar 2001
Number of Pages
102
DSTKIM No
CA011649
CANDIS No
516206
Format(s):
Hardcopy;Document Image stored on Optical Disk

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