Common SBT modes and physiology

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

1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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 likelihood of post-extubation success?

8. Take-home pearls

1. SBTs are stress tests of post-extubation physiology.
2. PS 5/5 for 30 minutes is a strong default for most ICU patients.
3. T-piece trials are valuable when false positives are costly or physiology demands it.
4. CPAP is reasonable but supported by less robust data.
5. Consistency, daily screening, and judgment matter more than the exact mode.

References and Further Reading

• Burns KEA, Khan J, Phoophiboon V, Trivedi V, Gomez-Builes JC, Giammarioli B, Lewis K, Chaudhuri D, Desai K, Friedrich JO. Spontaneous Breathing Trial Techniques for Extubating Adults and Children Who Are Critically Ill: A Systematic Review and Meta-Analysis. JAMA Netw Open. 2024 Feb 5;7(2):e2356794. doi: 10.1001/jamanetworkopen.2023.56794. PMID: 38393729; PMCID: PMC10891471.
• Burns KEA, Sadeghirad B, Ghadimi M, Khan J, Phoophiboon V, Trivedi V, Gomez Builes C, Giammarioli B, Lewis K, Chaudhuri D, Desai K, Friedrich JO. Comparative effectiveness of alternative spontaneous breathing trial techniques: a systematic review and network meta-analysis of randomized trials. Crit Care. 2024 Jun 8;28(1):194. doi: 10.1186/s13054-024-04958-4. PMID: 38849936; PMCID: PMC11162018.
• Subirà C, Hernández G, Vázquez A, Rodríguez-García R, González-Castro A, García C, Rubio O, Ventura L, López A, de la Torre MC, Keough E, Arauzo V, Hermosa C, Sánchez C, Tizón A, Tenza E, Laborda C, Cabañes S, Lacueva V, Del Mar Fernández M, Arnau A, Fernández R. Effect of Pressure Support vs T-Piece Ventilation Strategies During Spontaneous Breathing Trials on Successful Extubation Among Patients Receiving Mechanical Ventilation: A Randomized Clinical Trial. JAMA. 2019 Jun 11;321(22):2175-2182. doi: 10.1001/jama.2019.7234. Erratum in: JAMA. 2019 Aug 20;322(7):696. doi: 10.1001/jama.2019.11119. PMID: 31184740; PMCID: PMC6563557.
• Burns KEA, Wong J, Rizvi L, Lafreniere-Roula M, Thorpe K, Devlin JW, Cook DJ, Seely A, Dodek PM, Tanios M, Piraino T, Gouskos A, Kiedrowski KC, Kay P, Mitchell S, Merner GW, Mayette M, D’Aragon F, Lamontagne F, Rochwerg B, Turgeon A, Sia YT, Charbonney E, Aslanian P, Criner GJ, Hyzy RC, Beitler JR, Kassis EB, Kutsogiannis DJ, Meade MO, Liebler J, Iyer-Kumar S, Tsang J, Cirone R, Shanholtz C, Hill NS; Canadian Critical Care Trials Group. Frequency of Screening and Spontaneous Breathing Trial Techniques: A Randomized Clinical Trial. JAMA. 2024 Dec 3;332(21):1808-1821. doi: 10.1001/jama.2024.20631. PMID: 39382222; PMCID: PMC11581551.
• Mahul M, Jung B, Galia F, Molinari N, de Jong A, Coisel Y, Vaschetto R, Matecki S, Chanques G, Brochard L, Jaber S. Spontaneous breathing trial and post-extubation work of breathing in morbidly obese critically ill patients. Crit Care. 2016 Oct 27;20(1):346. doi: 10.1186/s13054-016-1457-4. PMID: 27784322; PMCID: PMC5081985.
• Yi LJ, Tian X, Chen M, Lei JM, Xiao N, Jiménez-Herrera MF. Comparative Efficacy and Safety of Four Different Spontaneous Breathing Trials for Weaning From Mechanical Ventilation: A Systematic Review and Network Meta-Analysis. Front Med (Lausanne). 2021 Nov 22;8:731196. doi: 10.3389/fmed.2021.731196. PMID: 34881255; PMCID: PMC8647911.​