Intrapleural pressure is the pressure of the air within the pleural cavity, between the visceral and parietal pleurae. This pressure changes during different phases of breathing.
Due to certain characteristics of the lungs, the intrapleural pressure is always lower than, or negative to, the intra-alveolar pressure. It remains approximately –4 mm Hg throughout the breathing cycle.
Therefore; if the intrapulmonary pressure was 760 mm hg then the intrapleural pressure will be (760 -4) mm Hg, that is 756 mm Hg
