As the volume of the thoracic cavity decreases, what happens to intra-pulmonary pressure?

When the volume of the thoracic cavity decreases, the intra-pulmonary pressure (the pressure within the lungs) increases. This relationship is explained by Boyle’s Law, which states that at a constant temperature, the pressure of a gas is inversely proportional to its volume. Consequently, as the volume of the thoracic cavity reduces during the process of exhalation, the gases within the lungs are compressed, leading to an increase in pressure.

This increase in intra-pulmonary pressure is what drives air out of the lungs and into the atmosphere, as air flows from an area of higher pressure to an area of lower pressure. Understanding this principle is essential for grasping the mechanical aspects of breathing and how the thoracic cavity's dynamics influence respiratory physiology.