In normal lung physiology the V/Q ratio is a measurement used to determine the efficacy and adequacy of<unk>  and<unk>  of the lung.<unk>  is the amount of air that reaches the lungs and<unk>  is the amount of blood flow to the lung. Any discrepancy between pulmonary blood flow and<unk>  is called V/Q<unk> . Ideally<unk>  and<unk>  should be equal with a V/Q ratio of 1, but the normal lung varies due to multiple factors such as gravity, size and patency of airways, and positioning. There is a higher<unk>  at the base of the lung than the apex of the lung. This causes a higher V/Q ratio at the apex compared to the base.The average V/Q ratio in a normal lung is about 0.8, with about 4 liters of oxygen and 5 liters of blood entering the lung per minute.Diseased lung can cause a V/Q<unk>  due to decreased blood flow or oxygenation.  This results in hypoxemia, which is a decreased oxygen concentration of blood.
Ventilation-perfusion mismatch
Right-to-left shunt
Hypoxic pulmonary vasoconstriction
Left-to-right shunt
Central neurogenic hyperventilation
Respiratory losses
Air embolism
Air trapping