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Acceleration-induced effects on baboon blood chemistry
A R Shahed1, J Barber, P M Werchan
1Operational Technologies Corporation, San Antonio, TX.
Aviation, Space, and Environmental Medicine
|July 1, 1993
Summary
High G-force exposure can cause pilots to lose consciousness (G-LOC) due to reduced brain blood flow. Studies show this triggers anaerobic glycolysis, increasing lactate, which may be a protective brain response.
Area of Science:
- Aerospace Medicine
- Neuroscience
- Physiology
Background:
- Gravity-induced loss of consciousness (G-LOC) has impacted aviation safety since the 1920s.
- G-LOC is primarily linked to decreased cerebral blood pressure and brain perfusion.
- Understanding cerebral metabolism during high +Gz exposure is crucial for pilot safety.
Purpose of the Study:
- To investigate cerebral metabolic changes during high +Gz exposure in baboons.
- To measure substrate availability and metabolic byproducts under simulated high-G conditions.
Main Methods:
- Adult baboons underwent multiple high +Gz exposures (2-6 G) on a human centrifuge.
- Venous blood samples were collected before, during, and after centrifuge runs.
- Blood gases, glucose, lactate, and creatine kinase activity were analyzed.
Main Results:
- Lactate and glucose concentrations tended to decrease during +Gz exposure and increase afterward.
- Cerebral blood flow reduction appears to stimulate anaerobic glycolysis, increasing lactate production.
- Creatine kinase activity remained largely unchanged, suggesting no significant muscle damage.
Conclusions:
- Reduced cerebral blood flow during +Gz exposure stimulates anaerobic glycolysis, leading to lactate accumulation.
- The observed decrease in blood lactate during exposure may be due to delayed release from tissues.
- G-LOC at high +Gz levels might be a protective mechanism to lower brain metabolic rate and prevent acidosis.