Figure 2. Physiologic response to hypoxia.

Response to hypoxia at altitude involves systemic arterial vasodilatation, hypoxic pulmonary vasoconstriction, and activation of peripheral chemoreceptors, with downstream effects including sympathetic activation, which increases blood pressure and cardiac output, as well as hyperventilation and pulmonary hypertension. Adapted from Bärtsch et al. ² © 2007 American Heart Association, Inc.