Ventilation-perfusion ratio is least at

In respiratory physiology, the ventilation/perfusion ratio (V/Q ratio or V/Q ratio) is a ratio used to assess the efficiency and adequacy of the matching of two variables: V or V - ventilation - the air that reaches the alveoli. Q or Q - perfusion - the blood that reaches the alveoli the capillaries Ref: guyton and hall textbook of medical physiology 12 edition page number:331,332,333