For efficient gas exchange, sufficient ventilation must reach each area of the lung to enable full oxygenation of the blood flowing through it – V/Q matching.

In a healthy person breathing spontaneously, the distribution of both ventilation and perfusion is lowest at the apices and increases steadily towards the bases of the lungs. They are thus well matched and oxygenation of pulmonary blood flow is efficient and virtually complete.

Question: Why does ventilation increase towards the base of the lungs?

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For efficient gas exchange, sufficient ventilation must reach each area of the lung to enable full oxygenation of the blood flowing through it – V/Q matching.

In a healthy person breathing spontaneously, the distribution of both ventilation and perfusion is lowest at the apices and increases steadily towards the bases of the lungs. They are thus well matched and oxygenation of pulmonary blood flow is efficient and virtually complete.

Question: Why does ventilation increase towards the base of the lungs?

Answer: Because they are on the most favourable part of the compliance curve.

Question: Why does perfusion increase towards the base of the lungs?

Click here for answer.

For efficient gas exchange, sufficient ventilation must reach each area of the lung to enable full oxygenation of the blood flowing through it – V/Q matching.

In a healthy person breathing spontaneously, the distribution of both ventilation and perfusion is lowest at the apices and increases steadily towards the bases of the lungs. They are thus well matched and oxygenation of pulmonary blood flow is efficient and virtually complete.

Question: Why does ventilation increase towards the base of the lungs?

Answer: Because they are on the most favourable part of the compliance curve.

Question: Why does perfusion increase towards the base of the lungs?

Answer: Because the effect of gravity decreases the perfusion pressure at the apices and increases it at the bases.