VPB 121: Veterinary Physiology - II (2+1)

VENTILATION-PERFUSION RELATIONSHIPS (V/Q)

• For optimal gas transfer to occur in the lung, ventilation and perfusion must be matched. In man for the whole lung, alveolar ventilation and pulmonary blood flow are both about 5 L/min. Therefore, for the whole lung V/Q is about 0.8 - 1.2. Local airway responses and hypoxic pulmonary vasoconstriction help match ventilation and perfusion.
• Low Oxygen in alveolus→ vasoconstriction
• High Oxygen in alveolus→ vasodilation
• High CO₂ in alveolus→ dilate bronchioles
• Low CO₂ in alveolus → constrict bronchioles