Weaning and Extubation
Weaning
=decreasing the amount of ventilator support
Approximately 26% to 39% of patients experience difficulty weaning from the ventilator.
PMID 19541716
PMID 21616997
In practice: Assist/Control ('CMV'), Pressure Support, SBT: 5/5 vs CPAP (0/5)
ATS/CHEST recommend 5/5 or 8/5 over CPAP. https://journal.chestnet.org/article/S0012-3692(16)62324-3/pdf
Is this patient ready to extubate?
Who should we assess for readiness to extubate?
Everyone who does not have a contraindication should be assessed for SBT / SAT*
=> 'run the numbers if their cause of respiratory failure has resolved, they're medically stable-enough, and their neurologic status suggests they can breath spontaneously
"CONCLUSIONS Daily screening of the respiratory function of adults receiving mechanical ventilation, followed by trials of spontaneous breathing in appropriate patients and notification of their physicians when the trials were successful, can reduce the duration of mechanical ventilation and the cost of intensive care and is associated with fewer complications than usual care."
https://pubmed.ncbi.nlm.nih.gov/8948561/
And paired "Wake up and Breathe" Trial
How would you study "readiness criteria"?
What's the problem with randomizing patients to extubation vs not?
How would we know if some patients that we think would do poorly, might actually do better?
What is an acceptable reintubation rate?
(2x2 graph): Given imperfect tests, what is the harm of reintubation vs remaining needless intubated.
Reintubation rate is roughly 20% in those at high risk (e.g. 65y or older, underlying cardiopulmonary disease)
####How to do the SBT
In folks who met "readiness criteria" - 30 minute PSV of 8 was better than 2 hour T piece SBT (non blinded RCT, non-protocolized post-extubation strategy) - higher first pass extubation rate and lower mortality. https://pubmed.ncbi.nlm.nih.gov/31184740/
Clinical Parameters
The cause of respiratory failure must be improved
Whatever led them to be intubated must have resolved
Secretions
When the ETT is in place, we are able to perform reliable deep suctioning. The must be making thin enough secretions, in a small enough amount, and with a strong enough cough, that they'll be able to clear their airways
Adequate Mental Status
Generally, able to follow commands
Cuff-leak
If you deflate the cuff, can air move around the ETT
Important in someone who you think may have swelling in their airway (e.g. intubated with airway trauma, airway swelling led to intubation, angioedema, very prolonged intubation)
Take down the cuff, have them cough. Observe for audible noise or difference in set vs returned Vt
Measurements of Respiratory Functioning
RSBI
Aka Tobin index
F / Vt
Threshold = 105
-Larger than 105 = not ready. (NPV 95%)
-Less than 105. Maybe ready (PPV 78%)
NIF
aka MIP. Maximum sub atmospheric pressure they can generate with an inspiratory effort
-30 cmH2O or more negative = associated with successful weaning.
-20 cmH2o or less negative = associated with failure of weaning
Vital Capacity
How large of a breath can the patient take in.
*Also assesses ability to follow commands.
Diaphragmatic Ultrasound
Overview in CHEST DOI:https://doi.org/10.1016/j.chest.2020.12.003
Extubation to...
Difference between "planned" vs "fail onto"
Fail onto BiPAP not recommended (ERS 2017 - https://erj.ersjournals.com/content/50/2/1602426) due to increased harm by delayed reintubation (NEJM https://www.nejm.org/doi/full/10.1056/NEJMoa032736)
NIV
If hypercapnia, COPD, Congestive heart failure
Nonblinded RCT - French ICUs: extubatne on NIV for 4+ hours and maintained 48h following extubation, with HFNC between, vs continuous HFNC => reduced reintubation rate (11.8% vs 18.2%). Benefit largest in hypercapneic patients (45mmHg). https://jamanetwork.com/journals/jama/fullarticle/2752582
HFNC
Recommended in all patients at high risk of extubation failure: older than 65 or with underlying cardiopulmonary conditions: ~20% risk of failure in this population (vs 10-15% in all comers)
Non-inferior to NIV, beneficial compared to NC in - Hernández G, Vaquero C, Colinas L, Cuena R, González P, Canabal A, et al. Effect of Postextubation High-Flow Nasal Cannula vs Noninvasive Ventilation on Reintubation and Postextubation Respiratory Failure in High-Risk Patients: A Randomized Clinical Trial. JAMA. 2016;316(15):1565–1574.
Combined Approach
Thille AW, Muller G, Gacouin A, Coudroy R, Decav `ele M, Sonneville R, et al.; HIGH-WEAN Study Group; REVA Research Network. Effect of postextubation high-flow nasal oxygen with noninvasive ventilation vs high-flow nasal oxygen alone on reintubation among patients at high risk of extubation failure: a randomized clinical trial. JAMA 2019;322: 1465–1475.
Reviewed in: https://www.atsjournals.org/doi/pdf/10.1164/rccm.202006-2312RR
Patients: 30 ICUs in France (REVA trial group), 2017-18, intubated for more than 24h and 65+ y/o or underlying cardiopulmonary conditions. (=EF<45%/Pulm Ed/CAD/AF, COPD, OHS, Restrictive lung dz). Excluded if on PAP already, NM dz, TBI, and unplanned extubation or DNI
Intervention: 48h of 50L HFNC vs (at least 4h NIV initially, and at least 12h per day over first 48h. HFNC when not NIV). If failing in either group - NIV not used to delay. Randomized at end of SBT.
Analysis: Primary outcome: reintubation rate (standardized criteria = severe respiratory failure = RR 25 / accessory muscules / pH <7.25 / CO2 45+ / FiO2 80%+ / P:F 100), hemodynamic failure requiring vasopressors, GCS < 12, or arrest). Variety of secondary outcomes.
Results: The reintubation rate at Day 7 was lower in patients receiving HFNO with NIV versus HFNO alone (11.8% vs. 18.2%; P = 0.02) and remained lower through ICU discharge (P = 0.009)
Critique: Non-blinded (of course) and a decision-based end-point (though they tried to protocolize). External validity to a given patient? (France ICU culture, thinner population, dependence on selection of who extubation is attempted in)