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Operation Everest II: coagulation system during prolonged decompression to 282 Torr
M Andrew1, H O'Brodovich, J Sutton
1Department of Pediatrics, McMaster University Health Sciences Centre, Chedoke-McMaster Hospitals, Hamilton, Ontario, Canada.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|September 1, 1987
Summary
High altitude exposure did not alter coagulation factors, but exercise increased factor VIII complex levels. The increase was blunted at higher altitudes, suggesting hypoxia does not significantly impact the coagulation cascade.
Area of Science:
- Physiology
- Altitude Medicine
- Hematology
Background:
- Thromboembolic events are a risk during high-altitude ascent.
- The coagulation cascade's role in altitude-related disorders requires further investigation.
Purpose of the Study:
- To examine the impact of simulated high altitude and exercise on coagulation factors and inhibitors.
- To determine if chronic hypoxia affects the coagulation cascade.
Main Methods:
- Eight subjects underwent progressive incremental exercise tests at sea level and simulated altitudes (380 and 282 Torr).
- Venous blood samples were analyzed for coagulation factors (II, V, VII, VIII complex, IX-XIII), inhibitors (antithrombin III, alpha 2-macroglobulin, alpha 2-antiplasmin, C1-esterase inhibitor, alpha 1-antitrypsin, protein C), and related markers (prekallikrein, high-molecular-weight kininogen, fibrinogen).
Main Results:
- Prolonged exposure to simulated high altitude did not change the concentration of coagulation factors or inhibitors.
- Exercise increased the circulating factor VIII complex at all altitudes, but this increase was diminished at higher altitudes.
- The exercise-induced increase in factor VIII complex correlated inversely with arterial O2 saturation and directly with workload, blood pH, and plasma lactate.
Conclusions:
- Gradual development of chronic hypoxia does not appear to significantly alter the coagulation cascade.
- Exercise-induced changes in the coagulation system are modulated by high-altitude conditions and associated physiological responses.