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Mathematical models for predicting straining G-level tolerances in reclined subjects
1Human Effectiveness Directorate Det 5, Air Force Research Laboratory, Brooks AFB, TX 78235-5118, USA.
Journal of Gravitational Physiology : a Journal of the International Society for Gravitational Physiology
|September 7, 2001
Summary
Mathematical models predict G-level tolerances for individuals in reclined positions. Reduced inspiratory capacity at greater seat-back angles necessitates the anti-G straining maneuver (AGSM), impacting tolerance limits.
Area of Science:
- Aerospace Medicine
- Human Physiology
- Biomechanical Engineering
Background:
- Subjects reclined greater than 55 degrees experience reduced inspiratory volume.
- This limitation restricts the maximum intrathoracic pressure achievable during the anti-G straining maneuver (AGSM).
- Consequently, an impaired AGSM capability lowers overall G-level tolerance.
Purpose of the Study:
- To develop mathematical models predicting G-level tolerances for subjects reclined between 55 and 75 degrees.
- To evaluate the potential of positive pressure breathing (PPB) to enhance G-level tolerance in reclined positions.
Main Methods:
- Modeling G-level tolerances based on seat-back angles from 55 to 75 degrees.
- Incorporating the effects of anti-G suit pressure (psi) into the tolerance predictions.
- Considering the influence of positive pressure breathing (PPB) on tolerance.
Main Results:
- Predicted G-level tolerances vary with seat-back angle and anti-G suit pressure.
- At 55 degrees, tolerances range from 11.7 to 12.7 G (7-10 psi).
- At 65 degrees, tolerances range from 12.1 to 12.8 G (6-9 psi).
- At 75 degrees, tolerances range from 13.4 to 14.2 G (5-8 psi).
Conclusions:
- G-level tolerance is significantly influenced by seat-back angle and anti-G suit pressure.
- Mathematical models provide predictions for G-tolerance in reclined postures.
- Positive pressure breathing (PPB) is a potential method for increasing G-level tolerance.
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