Question

Which of the following is/are higher at the base of the lung than at the apex: blood flow, V/Q, ventilation, P_O2, and P_CO2? Please explain.

I know the answers are blood flow, and ventilation, PCO2, but I need an explanation. Thank you!

Answer 1

Answer:

blood flow, and ventilation, PCO2.

Explanation:

Ventilation is nothing but distribution of gas volume that varies based onn the regional differences in resting lung volumes and transpulmonary pressure. Ventilation increases from the apex to the base of the lung in upright individual.

Distribution of pulmonary blood is affected primarly by gravity. The blood flow also increases from apex to base.

V/Q (ventilation/perfusion abnormality) is defined as an abnormal mismatching of gas exchange and pulmonary perfusion. It is much higher is the top of the lung, about 3.3. The V/Q ratio is higher at the apex (ventilation is lower at the apex and higher at the base but the regional difference isn't as huge for ventilation like it is for perfusion), so gas exchange is more efficient at the apex and results in the highest PO₂ in the lung (and lower PCO₂) when compared to the base.