What happens to air movement when atmospheric pressure exceeds intrapulmonary pressure?

When atmospheric pressure exceeds intrapulmonary pressure, air movement occurs from areas of higher pressure to areas of lower pressure. In this case, the higher atmospheric pressure outside the body pushes air into the lungs, where the intrapulmonary pressure is lower. During the process of expiration, the diaphragm and intercostal muscles relax, causing the thoracic cavity to decrease in volume. This decrease results in an increase in intrapulmonary pressure relative to atmospheric pressure, leading to airflow out of the lungs. Therefore, when atmospheric pressure is greater than intrapulmonary pressure, the air is expelled from the lungs to equalize the pressure difference.

This understanding is fundamental in grasping the mechanics of breathing and the roles that pressure differences play in pulmonary ventilation.