Which option best describes typical criteria to initiate a spontaneous breathing trial?

• A. Hemodynamic instability.
• B. Stable oxygenation with FiO2 ≤0.5 and PEEP ≤8-10.
• C. Active myocardial ischemia.
• D. Spontaneous breathing is not allowed.

Answer: (B)

Initiating a spontaneous breathing trial requires confirming the patient can maintain oxygenation and work of breathing with minimal ventilator support while remaining stable. The option describing stable oxygenation with FiO2 ≤ 0.5 and PEEP ≤ 8–10 cm H2O best fits that readiness picture. A FiO2 at or below 0.5 indicates the patient doesn’t depend on high inspired oxygen to keep oxygen levels adequate, and a modest PEEP of 8–10 cm H2O provides enough alveolar recruitment without indicating a need for heavy ventilator support. Together, these thresholds show the patient may tolerate breathing on their own.

The other scenarios point to conditions that would make a spontaneous breathing trial unsafe or inappropriate: hemodynamic instability implies potential decompensation during the trial; active myocardial ischemia signals insufficient cardiac reserve; and the statement that spontaneous breathing is not allowed directly contradicts the purpose of an SBT.