What condition can occur if the pressure gauge reads less than 0 or greater than 45?

• A. Hypotension
• B. Pneumothorax
• C. Barotrauma
• D. Hypoxemia

Answer: (C)

Pressure monitoring during ventilation is about keeping the airway pressures within a safe window to prevent lung injury. When the pressure in the circuit becomes too high—above about 45 cm H2O—the alveolar walls can overdistend and rupture. Air escapes into the interstitial space and can track into the pleural space or mediastinum, producing pneumothorax, pneumomediastinum, or subcutaneous emphysema—collectively referred to as barotrauma. A reading below zero usually signals a leak or disconnection in the circuit, which indicates a ventilation problem, but the classic risk of actual injury from high pressures is barotrauma.