An increase in TPP during inspiration leads to expansion of the lungs, as the force acting to expand the lungs, i.e., the TPP, is now superior to the inward elastic recoil exerted by the lungs. ... Decreased lung dimensions lead to the alveolar pressure surpassing the atmospheric pressure, as explained by the Boyle law.

What does a high intrapleural pressure mean?

When intrapleural pressure becomes positive, increasing the effort (i.e. intrapleural pressure) causes no further increase in air flow. This effort independence indicates that resistance to air flow is increasing as intrapleural pressure increases (dynamic compression).

Is intrapleural pressure positive?

Under physiological conditions the transpulmonary pressure is always positive; intrapleural pressure is always negative and relatively large, while alveolar pressure moves from slightly negative to slightly positive as a person breathes.