Hypoxic pulmonary vasoconstriction

From Wikipedia, the free encyclopedia

Hypoxic pulmonary vasoconstriction is the phenomenon when pulmonary arterioles vasoconstrict in the presence of hypoxia (low oxygen levels) without hypercapnia (high carbon dioxide levels).

The process is at first illogical, as low oxygen levels should theoretically lead to increased blood flow to the lungs to receive increased gaseous exchange.

It is explained, however, by the fact that constriction leads to more bloodflow to unused parts of the lungs, which increases the total area of lungs that are involved in gaseous exchange.

[edit] External links

• Overview at ccmtutorials.com

v • d • e Respiratory system, physiology: respiratory physiology

Volumes: lung volumes - vital capacity - functional residual capacity - respiratory minute volume - dead space - spirometry - body plethysmography - peak flow meter ventilation (V) (positive pressure) breath (inhalation, exhalation) - respiratory rate - respirometer - pulmonary surfactant - compliance - hysteresivity - airway resistance pulmonary circulation - perfusion (Q) - hypoxic pulmonary vasoconstriction - pulmonary shunt ventilation/perfusion ratio (V/Q) and scan - zones of the lung - gas exchange - pulmonary gas pressures - alveolar gas equation - hemoglobin - oxygen-haemoglobin dissociation curve (2,3-DPG, Bohr effect, Haldane effect) - carbonic anhydrase (chloride shift) - oxyhemoglobin - respiratory quotient - arterial blood gas - diffusion capacity - Dlco control of respiration: pons (pneumotaxic center, apneustic center) - medulla (dorsal respiratory group, ventral respiratory group) - chemoreceptors (central, peripheral) - pulmonary stretch receptors - Hering-Breuer reflex high altitude - oxygen toxicity - hypoxia

Several factors inhibit this process including increased cardiac output, hypocarbia, hypothermia, acidosis/alkalosis, increased pulmonary vascular resistance, inhaled anesthetics, calcium channel blockers, PEEP, HFV, isoproterenol, nitrous oxide, vasodilators.