<unk>  <unk> , also known as the Euler-Liljestrand mechanism, is a physiological phenomenon in which small<unk>  arteries constrict in the presence of alveolar<unk>  (low oxygen levels). By redirecting blood flow from poorly-ventilated lung regions to well-ventilated lung regions,<unk>  is thought to be the primary mechanism underlying ventilation/perfusion matching. The process might initially seem counterintuitive, as low oxygen levels might theoretically stimulate increased blood flow to the lungs to increase gas exchange. However, the purpose of<unk>  is to distribute bloodflow regionally to increase the overall efficiency of gas exchange between air and blood. While the maintenance of ventilation/perfusion ratio during regional obstruction of airflow is beneficial,<unk>  can be detrimental during global alveolar<unk>  which occurs with exposure to high altitude, where<unk>  causes a significant increase in total<unk>  vascular resistance, and<unk>  arterial pressure, potentially leading to<unk>  hypertension and<unk>  edema. Several factors inhibit<unk>  including increased cardiac output, hypocapnia, hypothermia, acidosis/alkalosis, increased<unk>  vascular resistance, inhaled anesthetics, calcium channel blockers, positive end-expiratory pressure (PEEP), high-frequency ventilation (HFV), isoproterenol, nitric oxide, and vasodilators.
Hypoxic pulmonary vasoconstriction
Histotoxic hypoxia
Central neurogenic hyperventilation
Coronary vasospasm
Exercise-induced bronchoconstriction
Cerebral hypoxia
Hypoxic ventilatory response
Hyperdynamic circulation