Ventilation-perfusion ratio is maximum at: (A) Apex of lung, (B) Base of lung, (C) Posterior lobe of lung, (D) Middle of the lung
Answer is A. Apical alveoli have low ventilation and perfusion per unit volume of the lung, whereas the basal alveoli have high ventilation and perfusion.
Ventilation-perfusion ratio and the PaO2 is maximum at the apex. PCO2 is maximum at the base.