Abrupt Deflation after Sustained Inflation Causes Lung Injury

Area of Science:

• Critical Care Medicine
• Pulmonary Physiology
• Mechanical Ventilation

Background:

• Mechanical ventilator management for acute respiratory distress syndrome (ARDS) typically focuses on parameter settings.
• The physiological consequences of ventilator disconnection, particularly abrupt deflation, are not well understood.

Purpose of the Study:

• To investigate whether abrupt lung deflation following a sustained inflation maneuver causes lung injury.
• To elucidate the mechanisms underlying potential lung injury induced by abrupt ventilator disconnection.

Main Methods:

• Male Sprague-Dawley rats were subjected to low tidal volume ventilation.
• Intervention group received positive end-expiratory pressure (PEEP) increase followed by abrupt deflation to zero PEEP.
• Lung function, injury markers (wet/dry ratio, microvascular leak), hemodynamics, and cardiac function were assessed.

Main Results:

• Abrupt deflation led to acute lung dysfunction and injury, characterized by decreased compliance and increased wet/dry ratio.
• Vascular leak occurred post-deflation, predominantly affecting the endothelium.
• Hemodynamic changes included increased left ventricular preload and afterload, leading to right ventricular failure. Gradual deflation did not cause injury.

Conclusions:

• Abrupt ventilator disconnection after sustained inflation can induce acute lung injury.
• The injury mechanism involves left ventricular decompensation, elevated pulmonary microvascular pressure, and subsequent endothelial damage.
• Pharmacological intervention (sodium nitroprusside) mitigated injury by preventing adverse hemodynamic changes.