Intrapleural pressure

Intrapleural pressure is the pressure within the pleural cavity, the thin, fluid-filled space between the two pulmonary pleurae (known as visceral and parietal) of each lung. A negative pressure, less than atmospheric pressure, usually exists within the intrapleural space. This is due to the elastic recoil of the lungs trying to collapse away from the chest wall, which is simultaneously trying to pull away from the lung.

Mechanism

The intrapleural pressure is sub-atmospheric; it is lower than the atmospheric pressure and is always negative, which is necessary to keep the lungs inflated. This negative intrapleural pressure is due to three main factors:

1. Surface tension of the alveolar fluid
2. The elasticity of the lung tissue
3. The connectivity of the pleural membrane

Changes in Intrapleural Pressure

During the process of inhalation and exhalation, the intrapleural pressure changes. It becomes more negative during inhalation as the chest wall expands out. Conversely, it returns to its resting negative value during exhalation.

Clinical Significance

Intrapleural pressure is clinically significant as it can be affected in many lung diseases, including pneumothorax and pleural effusion. In these conditions, the intrapleural pressure becomes equal to the atmospheric pressure, a state known as zero intrapleural pressure. This can cause the lung to collapse and potentially lead to respiratory failure.

See Also

• Pleural cavity
• Pneumothorax
• Pleural effusion
• Respiratory system

References

• 
  Intrapulmonary and Intrapleural Pressure