Liberation for Mechanical Ventilation

Steps for liberation

1. Optimize conditions
2. Assess readiness for extubation/spontaneous breathing trial (SBTs)
3. Conduct SBT daily with sedation holiday
4. Extubate if passes SBT
   1. to room air
   2. to NIV

Conditions need to be optimized

• respiratory
  • FiO2 < 40-50%
  • PEEP < 5-10 cm (more if obese)
    • can always extubate to CPAP if concerned about precipitating pulmonary edema
  • normal PaCO2 or etCO2
  • patient-triggered mode (e.g. PSV)
• cardiovascular
  • stable perfusion
  • stable heart rate
  • not on high level Vasopressors
• neuro
  • arousable
  • ideally following commands (e.g. minimal sedation)
• renal
  • no uncontrolled acid-base physiology
• gastrointestinal
  • NG feeds off for approx 6 hours or so. Due to risk of aspiration with elective airway procedure.
• underlying issue is resolved or managed

Assessment of readiness for extubation/SBT

• LOC satisfactory, and cooperative. Can they protect their airway?
• Can lift their head off the pillow, and arms off the bed. Do they have ICU-AW?
• Adequate cough with tracheal suctioning.
• Adequate gag with oropharyngeal suctioning.
• good tidal volumes with zero pressure support (>10 mL/kg IBW)
• Can overcome -20 cmH2O pressure trigger (adequate MIP). Can they generate enough negative pressure?
• Satisfactory audible/measured cuff leak. Presence of cuff leak predicts success. Absence of cuff leak may not predict failed extubation. See below.
• RSBI
  • classical RSBI per Yang-Tobin study (1991):
    • T-piece
    • first minute of SBT
    • spirometer used
    • resp rate (f) divided by VT in litres.
  • Zhang et al 2014 suggest you can use PSV 5/5-7 with a threshold of 75 to predict extubation failure

Daily Spontaneous Breathing Trials

Essentially, an SBT is the process of taking a still-intubated patient and then simulating the workload of spontaneous extubated breathing with the tube still in situ. The Awake and Breathing Controlled trial (ABC) showed that daily spontaneous awakening trial + SBT (SAT/SBT) resulted in more days breathing without assistance, shorter ICU length of stay, shorter hospital length of stay, and lower mortality than standard of care.

Assessing SBT Success

• adequate oxygenation
• adequate ventilation
• no signs of severe fatigue which can include the following
  • accessory muscle use, diaphoresis
  • high RSBI (Yang-Tobin study) > 105
• no other obvious complications from SBT (arrhythmia, bradycardia, hypotension, severe hypertension)

Duration, and T-piece vs PSV?

Classically, the options for performing an SBT were broad. One could choose either PSV (5-8/0-5), T-piece. Duration could be 30-120 minutes.

Evidence for equivocality:

1. Subira et. al (JAMA 2019) randomized 1153 adults at low-risk of re-intubation to SBTs with 30 minutes of PSV (8/0 cm H2O) versus 2 hours of T-piece ventilation. 82.3% vs 74% of patients were successfully extubated (remained free of mechanical ventilation 72 hours after first SBT), p=0.001. Re-intubation rates were the same, and there were no significant differences in ICU or hospital LOS. Hospital mortality was lower (10.4% vs 14.9% in-hospital, p=0.02)
2. CCM 2020 meta-analysis of 10 RCTs showed that there was no significant difference in the successful extubation rate or rate of reintubation between the T-piece group and PSV group. The pressure used in these studies varied from 5-18cm H2O and the PEEP varied from 0-8cm H2O, which is highly variable.
3. Na et al. (Resp Res 2022) examined PSV (8/0) vs T-piece and found no association of PSV with a higher rate of successful weaning compared with SBT using T-piece

Evidence for either PSV/shorter duration:

1. CHEST 2020 analysis showed that PSV (7/0) vs T-piece led to successful extubation in 67% vs 56% (p<0.01) of patients at high risk of re-intubation
2. latest American Thoracic Society guidelines for weaning recommend PSV spontaneous breathing trials instead of T-piece with moderate-quality evidence
3. Thille et al. (TIP-EX RCT in NEJM 2022) randomized 969 high-extubation risk patients to either PSV 8/0 or T-piece for ~1 hour. There was no significant difference in 4-week VFD, 24-h extubation rate, 7-d extubation rate, reintubation rates.

Address Potential Cuff Leak

Extubation to Respiratory Support

After a successful SBT and extubation, 10% to 25% of patients require reintubation, and reintubation is associated with higher mortality.

• Consider extubating to HFNC for most patients.
• Patients with Chronic obstructive pulmonary disease (COPD), CHF, OSA may benefit from extubation to Non-Invasive Ventilation > NIV for extubation and ventilator liberation

References

1. Alía I, Esteban A. Weaning from mechanical ventilation. Crit Care [Internet]. 2000 [cited 2021 Dec 21];4(2):72–80. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC137330/
2. Nickson C. Weaning from Mechanical Ventilation [Internet]. Life in the Fast Lane • LITFL. 2019 [cited 2021 Dec 21]. Available from: https://litfl.com/weaning-from-mechanical-ventilation/
3. Lermitte J, Garfield MJ. Weaning from mechanical ventilation. Continuing Education in Anaesthesia Critical Care & Pain [Internet]. 2005 Aug 1 [cited 2021 Dec 21];5(4):113–7. Available from: https://doi.org/10.1093/bjaceaccp/mki031
4. Boles J-M, Bion J, Connors A, Herridge M, Marsh B, Melot C, et al. Weaning from mechanical ventilation. European Respiratory Journal [Internet]. 2007 May 1 [cited 2021 Dec 21];29(5):1033–56. Available from: https://erj.ersjournals.com/content/29/5/1033
5. Liberation from the ventilator [Internet]. EMCrit Project. [cited 2021 Dec 21]. Available from: https://emcrit.org/ibcc/extubation/
6. https://derangedphysiology.com/required-reading/respiratory-medicine-and-ventilation/Chapter%20259/assessment-extubation-readiness
7. The Ventilator Book, W Owens MD