Hypoxic ventilatory decline: site of action.

Although superficially similar, HVD appears to arise from different mechanisms in the awake animal as compared with the anesthetized animal. Consequently, the good evidence supporting a central site of action for hypoxia in the genesis of HVD in the anesthetized animal cannot be used as evidence for a central site of action for hypoxia in the awake animal. In their paper on HVD in the awake cat, Long et al. (10) conclude: "The striking similarity between feline and human ventilatory responses to moderate hypoxia illustrated by this and previous experiments leads us to believe that it is likely similar mechanisms apply to both species. Thus it seems probable that working out the mechanisms of the ventilatory response to hypoxia in the awake cat will go a long way toward solving the same problems in humans." This activity should not neglect a consideration of whether adaptation at the carotid body during sustained hypoxia may be involved in the genesis of HVD in the awake state.