The Case of the False Imprisonment

In the FOAM community a great deal of time is spent discussing the appropriate manner of transitioning critically ill patients onto mechanical ventilation. A far larger portion of the practice of critical care is spent determining how best to liberate our patients from the ventilatory shackles with which we have bound them. The specifics of spontaneous breathing trials (SBT) vary wildly (1), based mostly on dogma passed down from one generation of intensivists to the next. These strategies range from the ultra-conservative 2-hour T piece trial to the extremely aggressive “pull and pray” method. As a whole we tend to favor a more conservative strategy, extubating only those patients who have proven themselves capable of tolerating the rigors of independent ventilation. But in a recent article published in JAMA, by Subirà et al (2), we are once again reminded that when it comes to liberation from mechanical ventilation our expectations of success may be too high.

Over a 15-month period Subirà et al enrolled patients in 18 ICUs throughout Spain. The authors randomized adult patients who had received mechanical ventilation for greater than 24-hours and fulfilled prespecified weaning criteria, to one of two SBT strategies, a 2-hour T-piece trial or a 30-minute pressure support (PS) trial. The decision to reconnect the patient to the ventilator for 1 hour prior to extubation, and the use of noninvasive ventilation or high-flow nasal cannula after extubation was left to the judgment of the treating clinician, but was determined prior to randomization.

Patients who successfully completed their SBT were extubated while those who failed were placed back on mechanical ventilation. 1153 were included in the final analysis, 578 in the 2-hour T-piece trial and 575 patients in the 30-minute PS trial. Overall the authors observed their primary outcome, successful extubation (defined as remaining free of mechanical ventilation 72 hours after the SBT), occurred in 473 patients (82.3%) in the PS group and 428 patients (74%) in the T-piece group (difference, 8.2%; 95% CI, 3.4%-13%). This 8.2% absolute difference did not come at the cost of an increase in reintubation within 72-hours of extubation (11.1% in the PSV group vs, 11.9% in the T-piece group). In addition, the PS group also had a lower in-hospital mortality (10.4% vs 14.9%) and 90-day mortality (13.2% vs 17.3%).

These results are fairly compelling and at the very least should persuade us to discard the 2-hour long T-piece trial for the vast majority of patients undergoing a weaning trial. It does not indicate that all SBTs should be conducted with PS using the setting chosen by these authors. Rather these results speak to a general approach to ventilator liberation. Traditionally our weaning strategies have been fairly conservative, generally favoring strategies that optimize specificity over sensitivity. So much so that we have never formally evaluated whether a failed SBT accurately predicts a cohort of patients who will fail a trial of extubation. In fact, retrospective data suggests that a large portion of patients who experience an unplanned extubation after failing an SBT will not require re-intubation (3). But our entire focus has been on how well any particular SBT predicts a patient’s ability to wean from the ventilator. In defense of our conservative approach to weaning from mechanical ventilation, observational data is often cited, which suggests that patients who fail a trial of extubation fare worse than those that are extubated without difficulty (4). But the question we should be asking is not, do patients who fail extubation do worse than those who do not? But rather, do patients who fail a trial of extubation fare worse than those in whom we never try in the first place?

While no study has directly asked this question, some have examined it in a tangential fashion. The BREATHE Trial, published in JAMA by Perkins et al, randomized adult patients admitted to the ICU (5), who were intubated for at least 48-hours and who had failed an SBT to either continued invasive mechanical ventilation, or immediate extubation and non-invasive positive pressure ventilation (NIPPV) at similar settings to just prior to extubation. NIPPV was than weaned in a protocolized fashion. Over a 3-year period the authors enrolled 364 patients, 182 randomized to each group. Not surprisingly 99.5% of the patients in the NIPPV weaning group underwent a trial of extubation, compared to only 78.6% of the traditional weaning strategy group. The number of patients who required reintubation did not statistically differ between groups (37.0 % in the noninvasive group vs 28.7% in the invasive group odds ratio, 1.54; 95% CI, 0.89-2.41), although the point estimate was in favor of the traditional weaning strategy. Most importantly, 63% of patients who failed their SBT but were extubated anyway, were liberated from the ventilator without difficulty. Additionally, mortality did not between the two groups, which suggests trying and failing does not lead to worse outcomes when compared to not trying at all. In fact, by all accounts the NIPPV group appeared to do better, requiring less invasive ventilation (median, 1 day vs 4 days), fewer total ventilator days (median, 3 days vs 4 days), and requiring less antibiotics for respiratory infection (60.4% vs 70.3%). There was even a trend towards a decreased rate of tracheostomy (23.6% vs 30.2%), though this difference did not meet statistical significance.

Subirà et al demonstrates very similar results. Although they did not extubate everyone who failed an SBT, by lowering the threshold required to pass, more patients were extubated in the PS group, allowing for a larger portion to be weaned from the ventilator without deleterious consequences. In fact the vast majority of studies have demonstrated when you make the SBT easier for the patients to complete, more patients do so successfully, which leads to a larger portion of patients undergoing a trial of extubation, in turn leading to a larger number of patients successfully liberated from the ventilator (6).

We have been content in confining patients capable of independent ventilation to be shackled to the mechanical ventilator, assuming that trying and failing is a less favorable outcome than simply never trying at all. But there is a growing body of literature which suggests that our current assessment strategies vastly underestimate our patients abilities to breath independently. Moreover, trials of extubation that fail do not seem to directly harm our patients. While we should balance the risks and benefits of a trial of extubation for every individual patient, it behooves us to relax the bonds with which we keep our patients confined to the mechanical ventilator and all the iatrogenic harms associated with its use.

Sources Cited:

Godard S, Herry C, Westergaard P, et al. Practice Variation in Spontaneous Breathing Trial Performance and Reporting. Can Respir J. 2016;2016:9848942.
Subirà C, Hernández G, Vázquez A, et al. 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;321(22):2175-2182.
Chao CM, Sung MI, Cheng KC, et al. Prognostic factors and outcomes of unplanned extubation. Sci Rep. 2017;7(1):8636.
Jaber S, Quintard H, Cinotti R, et al. Risk factors and outcomes for airway failure versus non-airway failure in the intensive care unit: a multicenter observational study of 1514 extubation procedures. Crit Care. 2018;22(1):236.
Perkins GD, Mistry D, Gates S, et al. Effect of Protocolized Weaning With Early Extubation to Noninvasive Ventilation vs Invasive Weaning on Time to Liberation From Mechanical Ventilation Among Patients With Respiratory Failure: The Breathe Randomized Clinical Trial. JAMA. 2018;320(18):1881-1888.
Burns KEA, Soliman I, Adhikari NKJ, et al. Trials directly comparing alternative spontaneous breathing trial techniques: a systematic review and meta-analysis. Crit Care. 2017;21(1):127.