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Rethinking Inspiratory Pressure Augmentation in Spontaneous Breathing Trials FREE TO VIEW

Ewan C. Goligher, MD, PhD; Michael E. Detsky, MD; Michael C. Sklar, MD; Vagia T. Campbell, BHA; Pam Greco, BEd; Andre C.K.B. Amaral, MD; Niall D. Ferguson, MD; Laurent J. Brochard, MD
Author and Funding Information

FINANCIAL/NONFINANCIAL DISCLOSURES: None declared.

aInterdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, ON, Canada

bDepartment of Medicine, Division of Respirology, University Health Network and Mount Sinai Hospital, Toronto, ON, Canada

cDepartment of Critical Care Medicine, Sunnybrook Health Sciences Centre, Toronto, ON, Canada

dKeenan Centre for Biomedical Research, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, ON, Canada

CORRESPONDENCE TO: Ewan C. Goligher, MD, PhD, Mount Sinai Hospital, 600 University Ave, Room 18-206, Toronto, ON, M5G 1X5, Canada


Copyright 2017, American College of Chest Physicians. All Rights Reserved.


Chest. 2017;151(6):1399-1400. doi:10.1016/j.chest.2017.02.033
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Published online

In issuing a conditional recommendation in favor of inspiratory pressure augmentation during spontaneous breathing trials (SBTs) in a recent issue of CHEST (January 2017), Ouellete et al noted that the available evidence informing the recommendation is at serious risk of bias. We highlight here some additional limitations and address other key issues to consider when evaluating the best technique for conducting SBTs.

Aside from the limitations identified by the authors, all four trials ascertained outcomes only in patients who passed the SBT but reported these outcomes for the entire cohort. Because SBT pass rates are higher when using pressure support vs a T-piece, higher numbers of extubation success and failure will occur in patients randomized to a pressure support SBT. The impact of this bias is apparent because, paradoxically, both extubation success and extubation failure occurred more frequently in patients randomized to receive pressure support (70.5% vs 63.4% and 16.4% vs 14.8%, respectively). Notably, two of the four trials do not report extubation failure rates. None of these trials provide unbiased estimates of relevant outcomes for clinical decision-making.

The SBT is used as a diagnostic test to predict successful liberation from ventilation by assessing the patient’s ability to tolerate the work of breathing after extubation. Given the impact of extubation failure on patient-centered outcomes, we believe clinicians should use the SBT technique that allows them to rule-in “successful extubation” with the greatest confidence; that is, a specific test with a high positive likelihood ratio for successful extubation.

The patient’s work of breathing postextubation is best matched by SBTs conducted using T-piece or zero airway pressure on the ventilator. Additional support reduces the work of breathing by 20% to 40%, potentially masking the risk of postextubation distress from cardiac failure or excess respiratory loading. Compensating for the resistance of the endotracheal tube or the ventilator circuit is unnecessary because upper airway resistance is increased after extubation, and modern ventilators offer minimal loads., Because T-piece testing best matches the postextubation respiratory load, it is likely more specific than pressure support ventilation for successful extubation.

Recommending a test that applies an unrealistically low work of breathing compared with that experienced postextubation puts fragile patients at risk of harm. Clinicians may take into account many parameters aside from the test alone when considering extubation, but SBTs using pressure support may misinform a complex decision. For these reasons, we advocate the use of T-piece or zero airway pressure when conducting SBTs.

References

Ouellette D.R. .Patel S. .Girard T.D. .et al Liberation from mechanical ventilation in critically ill adults: an official American College of Chest Physicians/American Thoracic Society clinical practice guideline: inspiratory pressure augmentation during spontaneous breathing trials, protocols minimizing sedation, and noninvasive ventilation immediately after extubation. Chest. 2017;151:166-180 [PubMed]journal. [CrossRef] [PubMed]
 
Sklar MC, Burns K, Rittayamai N, et al. Effort to breathe with various spontaneous breathing trial techniques. A physiological meta-analysis [published online ahead of print October 21, 2016].Am J Respir Crit Care Med.http://dx.doi.org/10.1164/rccm.201607-1338OC.
 
Cabello B. .Thille A.W. .Roche-Campo F. .Brochard L. .Gómez F.J. .Mancebo J. . Physiological comparison of three spontaneous breathing trials in difficult-to-wean patients. Intensive Care Med. 2010;36:1171-1179 [PubMed]journal. [CrossRef] [PubMed]
 
Straus C. .Louis B. .Isabey D. .Lemaire F. .Harf A. .Brochard L. . Contribution of the endotracheal tube and the upper airway to breathing workload. Am J Respir Crit Care Med. 1998;157:23-30 [PubMed]journal. [CrossRef] [PubMed]
 
Richard J.C. .Carlucci A. .Breton L. .et al Bench testing of pressure support ventilation with three different generations of ventilators. Intensive Care Med. 2002;28:1049-1057 [PubMed]journal. [CrossRef] [PubMed]
 

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References

Ouellette D.R. .Patel S. .Girard T.D. .et al Liberation from mechanical ventilation in critically ill adults: an official American College of Chest Physicians/American Thoracic Society clinical practice guideline: inspiratory pressure augmentation during spontaneous breathing trials, protocols minimizing sedation, and noninvasive ventilation immediately after extubation. Chest. 2017;151:166-180 [PubMed]journal. [CrossRef] [PubMed]
 
Sklar MC, Burns K, Rittayamai N, et al. Effort to breathe with various spontaneous breathing trial techniques. A physiological meta-analysis [published online ahead of print October 21, 2016].Am J Respir Crit Care Med.http://dx.doi.org/10.1164/rccm.201607-1338OC.
 
Cabello B. .Thille A.W. .Roche-Campo F. .Brochard L. .Gómez F.J. .Mancebo J. . Physiological comparison of three spontaneous breathing trials in difficult-to-wean patients. Intensive Care Med. 2010;36:1171-1179 [PubMed]journal. [CrossRef] [PubMed]
 
Straus C. .Louis B. .Isabey D. .Lemaire F. .Harf A. .Brochard L. . Contribution of the endotracheal tube and the upper airway to breathing workload. Am J Respir Crit Care Med. 1998;157:23-30 [PubMed]journal. [CrossRef] [PubMed]
 
Richard J.C. .Carlucci A. .Breton L. .et al Bench testing of pressure support ventilation with three different generations of ventilators. Intensive Care Med. 2002;28:1049-1057 [PubMed]journal. [CrossRef] [PubMed]
 
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