Mechanical ventilation, essential for critically ill patients, contrasts with natural respiration, primarily due to differences in pleural pressure (Ppleural ). Natural inspiration decreases Ppleural , pulling the lungs away from the thoracic wall, whereas positive pressure inspiration increases Ppleural , pushing the lungs against the thoracic wall. This shift has several consequences. First, elevated Ppleural during positive pressure ventilation can lead to cyclic airway closure, particularly in the dependent lung regions. This increases the risk of atelectasis, that impairs oxygenation and may lead to further complications such as pneumonia. Second, the increase in Ppleural disrupts the balance maintained by negative Ppleural and capillary forces. This disruption reduces the lubricating pleural fluid between the pleurae, increasing friction and shear stress on the lung tissues, which may lead to damage and conditions such as ventilator-induced lung injury and pneumothorax. Furthermore, airway closure can worsen lung compliance, making mechanical ventilation more challenging and increasing the risk of lung overstretching. This necessitates careful management of ventilation settings, particularly the use of positive end-expiratory pressure (PEEP) and recruitment maneuvers to minimize these adverse effects. Protective strategies, such as synchronizing mechanical ventilation with the patient's breathing efforts, prone positioning, and careful application of PEEP, are crucial in reducing Ppleural and its associated risks. Since negative pressure ventilation (NPV) inherently lowers Ppleural , it may help avoid many of the adverse side effects previously discussed. Therefore, reconsidering and reintroducing NPV in a modern context should be seriously explored.
Keywords: Mechanical ventilation; pleural pressure; pneumothorax; ventilator induced lung injury (VILI).
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