Mar 032013
 
"Trach Collar" Trials Beat Pressure Support for Long-Term Ventilator Weaning

By Blair Westerly, MD

Patients requiring prolonged mechanical ventilation linger in ICUs and long-term acute care hospitals for weeks, accounting for a significant portion of intensive care unit costs and often suffering serious complications while dependent on the ventilator. Despite this issue's rising importance, the best method of helping these vulnerable patients escape the ventilator remains unknown. The most common weaning methods for patients on mechanical ventilation (spontaneous breathing trials and pressure support) have not been evaluated in patients receiving care at long-term acute care hospitals (LTACHs). A trial by Jubran et al in JAMA addressed the question and suggested that physicians may be too timid in challenging these patients with "trach collar" (oxygen-only) trials, unnecessarily prolonging their time on mechanical ventilation.

What They Did

Randomized study of stable patients in a single LTACH of pressure support versus tracheostomy collar trials. Upfront, all patients had received mechanical ventilation for at least 21 days and developed respiratory distress with a screening procedure (120-hour tracheostomy collar trial with humidified oxygen only).  Patients were stratified into two groups based on the amount of time before failing the screening procedure, either 0 to 12 hours (early-failure) or 12 to 120 hours (late-failure). They were then randomized to two weaning groups, either trach collar or pressure support. Here is how each group approached weaning:

  • Tracheostomy collar:
    • For the first two days patients were allowed to breathe unassisted for maximum of 12 hours before being reconnected to the ventilator and assist control ventilation
    • Day 3, the 5-day process of discontinuing mechanical ventilation was started, allowing the patient to breathe unassisted for up to 24 hours each day as tolerated
  • Pressure support group:
    • PS was started at 14 cm H2O and decreased three times daily by 2 cm H2O if patient looked good for preceding 6 hours
    • Max reduction in PS was 6 cm H2O in a 24-hour period.
    • Once PS of 6 cm H2O was tolerated for at least 12 hours, the 5 day process of ventilator discontinuation was started with the patient breathing unassisted through the tracheostomy up to a maximum of 24 hours each day (this part was same as trach collar group, eAppendix for article).

Primary outcome was weaning duration starting with the time of randomization. Weaning success was defined as five days of unassisted breathing (then reanalyzed with using seven days to compare results because of an expert consensus published after enrollment began).  Patients were excluded if they were unstable, had certain neurological deficits or had poor overall prognosis.

Because the trial could not be blinded during weaning, rigid weaning criteria were used in each study group and data was blinded to those analyzing it after collection.  Several analytic techniques were used to adjust for baseline covariates identified as contributing to weaning duration.

 

What They Found
  • 32% of patients enrolled passed the initial trach collar challenge and were considered weaned before randomization!
  • Overall, five covariates were associated with time required for successful weaning:

(1)  age

(2)  ventilator duration before randomization

(3)  frequency to tidal volume ratio

(4)  maximal inspiratory pressure

(5)  weaning technique

  • When looking at the entire cohort, weaning time was significantly shorter in the tracheostomy collar group than in the pressure support group (15 d vs 19 d).  When adjusted for baseline covariates, the hazard ratio for weaning was higher in the tracheostomy collar group than the pressure support group.
  • In Cox modeling, the aforementioned covariates 1-4 were associated with weaning duration in the early-failure group but weaning method was not.
  • However, only weaning method was associated with weaning duration in the late-failure group and PS prolonged weaning compared to tracheostomy collar trials in the late-failure group.
  • There was no difference in survival.

 

What It Means

In 1995, Esteban et al famously showed that many mechanically ventilated patients weren't being given a fair chance by their doctors: they could escape the ventilator simply by placing them on spontaneous breathing trials and extubating them an hour or two later. This JAMA trial, while needing validation and confirmation, may extend that premise to more ventilator-dependent, chronically critically ill patients.

Patient-related factors are still the primary determinants for weaning in those who are sicker with less endurance (early-failure group). But, for those closer to liberation from mechanical ventilation, this study suggests weaning method plays a larger role and tracheostomy collar trials may be a more efficient than pressure support weaning.  Weaning method does not impact mortality.  Perhaps most notable for those of us not working in LTACHs is that almost one third of patients enrolled (160/500) passed the initial tracheostomy collar trial challenge, suggesting that they could have been weaned without ever being transferred to the LTACH and that intensivists may become less aggressive with weaning once the decision to transfer to LTACH has been made.

takeawayClinical Takeaway: Patients may be less "ventilator dependent" than we think, even after weeks of prolonged respiratory failure. A closely monitored "trach collar" trial may be justified in many more patients than we intuitively believe are ready to wean from the ventilator.

Jubran A et al. Effect of pressure support versus unassisted breathing through a tracheostomy collar on weaning duration in patients requiring prolonged mechanical ventilation. A randomized trial. JAMA 2013;309(7).

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“Trach collar” beats pressure support trials for long-term ventilator weaning (RCT)