Dr Henry Jefferson, Consultant Anaesthetist
#QuestionFeedback 13. V/Q ratio - Apex vs Base A question was raised about why the V/Q ratio is higher at the lung apex despite both ventilation and perfusion increasing towards the base. The key is that perfusion increases proportionately MORE than ventilation. Consequently, the V/Q ratio falls from apex to base. This also explains why alveolar PO₂ is higher and PCO₂ lower at the apex. Regional alveolar gas composition depends on the V/Q ratio, rather than absolute ventilation alone.