Question

if a person holds his breath after expiration for 60 seconds ,how could the exchange of gases takes place during the period

Answer 1

We have an equilibrium between gases dissolved in our blood and gases in our alveolae. The law is Henry’s law. The amount of dissolved gases in a fluid is directly proportional to the partial pressure of gases above the fluid.

When you breathe in, partial pressure of oxygen is 1/5 of an atmosphere and nitrogen is 4/5 of an atmosphere. Our bodies use oxygen so it goes out of blood, hence out of alveolae. Carbon dioxide our bodies produce hence its concentration goes up in the blood and subsequently in alveolae. Nitrogen is neither consumed not produced so it stays approximately the same.

After expiration you have in your lungs only residual volumen and oxygen continues to go down and carbon dioxide goes up.

Now, after several seconds, maybe even a minute, you will feel a strong urge to breathe in. That’s because the level of carbon dioxide becomes very high in your blood and in your alveolae.