Hypoxic pulmonary vasoconstriction

From Wikipedia, the free encyclopedia

Hypoxic pulmonary vasoconstriction is a physiological phenomenon in which pulmonary arteries constrict in the presence of hypoxia (low oxygen levels) without hypercapnia (high carbon dioxide levels), redirecting blood flow to alveoli with higher oxygen tension.

The process might at first seem illogical, as low oxygen levels should theoretically lead to increased blood flow to the lungs to receive increased gaseous exchange. However, it is explained by the fact that constriction leads to increased bloodflow to better-aerated areas of the lung, which increases the total area involved in gaseous exchange.

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.

[edit] External links

• American Thoracic Society
• American Journal of Physiology, Lung Cellular and Molecular Physiology
• Overview at ccmtutorials.com

v • d • e Respiratory system, physiology: respiratory physiology Volumes lung volumes - vital capacity - functional residual capacity - respiratory minute volume - closing capacity - dead space - spirometry - body plethysmography - peak flow meter - thoracic independent volume - bronchial challenge test Airways ventilation (V) (positive pressure) - breath (inhalation, exhalation) -respiratory rate - respirometer - pulmonary surfactant - compliance - hysteresivity - airway resistance Blood pulmonary circulation - perfusion (Q) - hypoxic pulmonary vasoconstriction - pulmonary shunt Interactions 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) Insufficiency high altitude - oxygen toxicity - hypoxia