Which of the following is true about ventilation and perfusion in alveoli in an erect posture: (A) Ventilation/perfusion ratio is maximum at apex, (B) Ventilation/perfusion ratio is maximum at base, (C) Ventilation is maximum at apex, (D) Perfusion is maximum at apex
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.