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Normally, the pressure within the pleural cavity is slightly less than the atmospheric pressure, which is known as negative pressure. [1] When the pleural cavity is damaged or ruptured and the intrapleural pressure becomes greater than the atmospheric pressure, pneumothorax may ensue. Intrapleural pressure is different from intrathoracic ...
The pleural cavity transmits movements of the ribs muscles to the lungs, particularly during heavy breathing. During inhalation the external intercostals contract, as does the diaphragm. This causes the expansion of the chest wall, that increases the volume of the lungs. A negative pressure is thus created and inhalation occurs.
This is called the pleural cavity (also pleural space). [2] It contains a tiny amount of serous fluid (pleural fluid) secreted by the pleurae, at an average pressure that is below the atmospheric pressure under healthy conditions. The two lungs, each bounded by a two-layered pleural sac, almost fill the thoracic cavity.
Transpulmonary pressure is the difference between the alveolar pressure and the intrapleural pressure in the pleural cavity. During human ventilation, air flows because of pressure gradients. P tp = P alv – P ip. Where P tp is transpulmonary pressure, P alv is alveolar pressure, and P ip is intrapleural pressure.
This allows one to monitor the sub-atmospheric pressure very close to the pleural space; therefore, the system works correctly, irrespective of where it is placed. Data measured next to the pleural space comes quite close to the real pressure within the pleural space [6] Shortened drainage time: Healing is a dynamic process.
The pleural space is maintained in a constant state of negative pressure (in comparison to atmospheric pressure). If the chest wall, and thus the pleural space, is punctured, blood, air or both can enter the pleural space. Air and/or blood rushes into the space in order to equalise the pressure with that of the atmosphere.
Once air enters the pleural cavity, the intrapleural pressure increases, resulting in the difference between the intrapulmonary pressure and the intrapleural pressure (defined as the transpulmonary pressure) to equal zero, which cause the lungs to deflate in contrast to a normal transpulmonary pressure of ~4 mm Hg. [28]
With inhalation, the intrapleural pressure (the pressure within the pleural cavity) of the lungs decreases. Relaxing the diaphragm during expiration allows the lungs to recoil and regain the intrapleural pressure experienced previously at rest. Elastic recoil is inversely related to lung compliance.