Dead space (lungs) Physiology

[Afina91]

Hi! Does someone know why a dead space doesn't increase during Forced inspiration (i.e. it's value is constant~150 ml), despite the fact that small bronchioles (like alveoles) also increase in diameter (distend) (due to increased positive transairway pressure) and due to Boyle's law the volume should also increase?

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[AnatomyGrey12]

The volume does increase in the alveoli. Dead space is the volume that is not involved in gas exchange so is not affected by inspiration or expiration. Think of it as the volume that is always present in the lungs regardless of whether you are breathing in or breathing out.

I recommend using BRS Physiology, she lays out the concepts very succinctly with good practice Qs at the end