117. Pulm PEEPs Pearls: Spontaneous Breathing Trials

This week’s Pulm PEEPs Pearls episode is all about spontaneous breathing trials (SBTs). SBTs are a standard part of the daily practice in the intensive care unit, but the exact methods vary across ICUs and institutions. Listen in to hear about the most common methods of SBTs, the physiology of each method, and what the evidence says. Contributors This episode was prepared with research by Pulm PEEPs Associate Editor George Doumat. Dustin Latimer, another Pulm PEEPs Associate Editor, assisted with audio and video editing. Key Learning Points What an SBT is really testing An SBT is a stress test for post-extubation work of breathing, not just a ventilator check. The goal is to balance sensitivity and specificity: Too hard → unnecessary failures and delayed extubation Too easy → false positives and higher risk of reintubation Common SBT modalities and how they compare T-piece No inspiratory support and no PEEP Highest work of breathing Most “physiologic” but often too strict Pressure support (PS) + PEEP (e.g., 5/5 or 8/5) Offsets ETT resistance and provides modest assistance Easier to pass than T-piece CPAP (0/5) No inspiratory help, but provides PEEP to counter ETT resistance Sits between PS and T-piece in difficulty Evidence favors pressure-supported SBTs for most patients Large meta-analysis (~6,000 patients, >40 RCTs): Pressure-supported SBTs increase successful extubation (~7% absolute benefit) No increase in reintubation rates Trials (e.g., FAST trial): Patients pass SBTs earlier Leads to earlier extubation and fewer ventilator-associated risks Bottom line: A 30-minute PS 5/5 SBT is evidence-based and appropriate for most stable ICU patients When a T-piece still makes sense T-piece SBTs are useful when: Cost of reintubation is high Difficult airway Prior failed extubation Pretest probability of success is low Prolonged or difficult weaning Tracheostomy vs extubation decisions Need to mimic physiology without positive pressure In LV dysfunction or pulmonary edema even small amounts PEEP may significantly improve physiology Some centers use a hybrid approach: PS SBT → short confirmatory T-piece before extubation CPAP as a middle ground Rationale: Allows full patient effort while compensating for ETT resistance Evidence: Fewer and smaller trials Possible modest improvement in extubation success No clear mortality or LOS benefit Reasonable option based on patient physiology, institutional protocols, and clinician comfort No single “perfect” SBT mode Across PS, T-piece, CPAP, and newer methods (e.g., high-flow via ETT) there are no consistent differences in mortality or length of stay What matters most: Daily protocolized screening Thoughtful bedside clinical judgment Matching SBT difficulty to patient-specific risk Institutional variation is normal—and acceptable Examples: PS 10/5 in postoperative surgical ICU patients PS 5/0 as an intermediate difficulty option Key question clinicians should ask: What does passing or failing this specific SBT tell me about this patient’s l