Related Experiment Videos
An objective determination of +Gz acceleration tolerance
H Sandler1, S A Rositano, E P McCutcheon
1Biomedical Research Division, National Aeronautics and Space Administration, Ames Research Center, Moffett Field, CA 94035, USA.
Acta Astronautica
|May 1, 1977
Summary
New Doppler technology objectively measures head blood flow during high Gz acceleration. This method reliably predicts vision loss and unconsciousness, improving pilot safety and protective gear evaluation.
Area of Science:
- Aerospace Medicine
- Biomedical Engineering
- Human Physiology
Background:
- Human tolerance to +Gz acceleration traditionally relied on subjective visual cues.
- Lack of objective physiological endpoints limited assessment of acceleration effects.
- Previous methods could not reliably predict G-induced loss of consciousness (G-LOC).
Purpose of the Study:
- To develop and validate an objective method for assessing human tolerance to +Gz acceleration.
- To correlate head blood flow changes with visual and consciousness endpoints.
- To establish a reliable safety monitoring system for high-G environments.
Main Methods:
- Utilized a noninvasive transcutaneous Doppler flow system with miniature ultrasound sensors.
- Monitored blood flow velocity in the temporal arteries on the forehead.
- Correlated Doppler measurements with subjective visual loss and G-LOC during centrifuge runs.
Main Results:
- Objective changes in temporal artery flow velocity consistently preceded visual degradation.
- Complete cessation of blood flow (6 seconds) always preceded central light loss and G-LOC.
- Demonstrated a strong correlation between altered blood flow and acceleration-induced physiological effects.
Conclusions:
- Transcutaneous Doppler flow measurement provides a reliable, objective endpoint for +Gz acceleration tolerance.
- This method can assess the efficacy of protective equipment and maneuvers.
- It offers potential as a safety monitor in high-performance aircraft and spacecraft re-entry.