Hypoxic pulmonary vasoconstriction

• Hypoxic pulmonary vasoconstriction:

  • In respiratory disease areas of poor ventilation lead to a decrease in gas exchange & hypoxia
  • When PaO2 falls to ~ 6 Kpa / SaO2 is at low 80's hypoxia is sensed by receptors in arterioles
  • Arterioles passing through area of poor ventilation constrict to minimise V/Q mismatch
  • Blood flow is redirected to area with good ventilation to facilitate gas exchange
• Clinical relevance HPVC

  • Persistent HPVC occurs in chronic respiratory disease (COPD)
  • Pulmonary arterioles have a decrease in diameter due to vasoconstriction
  • Therefore increase in resistance to blood flow
  • To maintain blood flow to lungs, the right side heart must work hard
  • Right side heart hypertrophy
  • Ultimately leads to right sided heart failure
  • Cor Pulmonale:
  • abnormal enlargement of the right side of the heart as a result of disease of the lungs or the pulmonary blood vessels
• Pulmonary capillary recruitment:

  • In areas where ventilation is high additional vessels in the pulmonary arteriole bed are recruited to optimise V/Q matching and maximise gas exchange