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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, or pleural space (or sometimes intrapleural space), is the potential space between the pleurae of the pleural sac that surrounds each lung. A small amount of serous pleural fluid is maintained in the pleural cavity to enable lubrication between the membranes , and also to create a pressure gradient .
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.
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]
NPPE develops as a result of significant negative pressure generated in the chest cavity by inspiration against an upper airway obstruction. These negative pressures in the chest lead to increase venous supply to the right side of the heart while simultaneously creating more resistance for the left side of the heart to supply blood to the rest of the body (). [4]
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.
It's when the zone of apposition ( the portion of the diaphragm in contact with the parietal pleura during expiration in the base of the pleural cavity') is reduced by the flattening of the diaphragm during inspiration and the pressure in the last intercostal spaces changes from intra-abdominal to intra-thoracic pressure.