During inspiration when the diaphragm contracts, the intrapleural pressure becomes:
The intrapleural pressure is always negative to the atmospheric pressure. During inspiration it is -6mHg and during expiration it is -2mmHg. Intrapleural pressure prevents collapse of lungs.
Intra alveolar pressure is -4mm during inspiration and +4mm Hg during expiration. It helps in flow of air in and out of alveoli and helps in exchange of gases.
More negative
Less negative
Positive
Equal to the intra alveolar pressure