Ventilation-perfusion relationships (V/Q) in animals
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