Key result
Acute prolonged hypoxia in dogs significantly increased cardiac index only during severe hypoxia (5.75% O2), indicating a hypoxic threshold for cardiac output elevation between 6.0 and 9.0% O2.
Why the study?
Does acute prolonged hypoxia alter cardiovascular dynamics in intact anesthetized dogs?
Does acute prolonged hypoxia alter cardiovascular dynamics in intact anesthetized dogs?
In an anesthetized dog model, the hypoxic threshold for significant elevations of cardiac output is between 6.0 and 9.0% O2.
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Findings in anesthetized dogs warrant no clinical extrapolation; leaves open hypoxic cardiac output thresholds in humans.
Borgia et al. (1977) studied this question. Acute prolonged hypoxia (5.75, 9.0, or 12.0% oxygen in nitrogen) vs. Normoxia was evaluated on Cardiovascular dynamics including cardiac index and coronary blood flow. Acute prolonged hypoxia in dogs significantly increased cardiac index only during severe hypoxia (5.75% O2), indicating a hypoxic threshold for cardiac output elevation between 6.0 and 9.0% O2.
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