Pressure support ventilation (PSV) mode on the ICU ventilator helps wean patients from mechanical ventilation. What is the minimum level of pressure support that overcomes endotracheal tube resistance during a spontaneous breathing trial?

• A 0–2 cmH2O
• B 12–15 cmH2O
• C 20 cmH2O
• D 5–8 cmH2O ✓

Explanation

A standard 8.0 mm ID endotracheal tube imposes approximately 4–6 cmH2O resistance per litre/second of gas flow. To compensate for this imposed work of breathing during a spontaneous breathing trial (SBT), pressure support of 5–8 cmH2O is commonly applied to approximate unassisted breathing through the upper airway. This is sometimes called an 'SBT with minimal support.' T-piece trials (0 cmH2O) impose higher work of breathing. Patients who tolerate PSV 5–8 cmH2O with satisfactory oxygenation (SpO2 ≥95%), RR <25/min, and tidal volume >5 mL/kg are candidates for extubation.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

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