A Model of Cardiovascular Performance During Sustained Acceleration

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Authors
  1. Walsh, C.
  2. Cirovic, S.
  3. Fraser, W.D.
Corporate Authors
Defence and Civil Inst of Environmental Medicine, Downsview ONT (CAN)
Abstract
During aerial combat maneuvers, Gz can cause visual impairment or loss of consciousness (G-LOC). Anti-G suits, positive pressure breathing, and anti-G straining maneuvers reduce the risk of G-LOC. However, complex G-profiles are problematic. To assist in designing G-protective measures for such profiles, we are developing a model of human cardiovascular performance. We present preliminary results from a model that deals with the mechanical aspects of cardiovascular response to Gz. Physiological reflexes are neglected. We consider a closed loop vascular network with a time varying elastance heart model. Blood flow is modeled by a one-dimensional (1-D) approximation: a pair of first order partial differential equations govern continuity and momentum. The blood pressure is determined by the external pressure and a tube law. The dominant physical phenomenon is wave propagation. The vasculature is modeled as a network of uniform flexible tubes. Valves are placed at the entrances and exits to the ventricles, and in the veins. The equations are solved numerically using a split coefficient matrix method. The algorithm is first order, and it is suited to wave propagation. The boundary conditions are implemented using the method of characteristics. The results show cardiac output falling as Gz increases and rising again when Gz is reduced. TRUNCATED
Keywords
G-Induced Loss of Consciousness (G-LOC);High Sustained G-forces (HSG)
Report Number
DCIEM-98-P-91 — Paper
Date of publication
01 Mar 1999
Number of Pages
9
DSTKIM No
CA000005
CANDIS No
511940
Format(s):
Hardcopy;Document Image stored on Optical Disk

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