One of the perennial issues in Critical Care is that of the ‘problem patient’ that doesn’t seem to want to wean off ventilatory support. I am sure you know the situation well.
You treat a patient and support them through their critical illness to the point where they show all the signs that they are ready to wean. Next thing you know, you are locked into a frustrating cycle of protracted weaning. You try one thing. Then another. But to no avail.
I have often heard it said that there is no evidence for one weaning strategy or another. So what is the truth to this statement?
The only evidence there is, is simply to have a consistent weaning plan. So out of curiosity, I decided to look into it. Is there a Holy Grail of weaning strategies that trials have shown to be superior?
Looking through the literature, there is a wealth of research examining the minutiae of respiratory weaning and its effects on various clinical outcomes.
Not wanting to get bogged down, I opted to go ‘big’ and look at a couple of the available relevant meta-analyses. Bare in mind, this is a simple blog designed to be a quick on the fly, FOAMed based aide memoir. You can click on the links here to read more detail.
This meta-analysis evaluated the effectiveness of pressure support ventilation versus a T-tube, for weaning adults with respiratory failure. It measured weaning success along with a number of additional clinical outcomes. It included 9 RCTs with 1208 mechanically ventilated patients comparing a T-tube with pressure support for spontaneous breath trials.
There was no difference between pressure support and T-tube for:
- Weaning success (RR 1.07, 95% CI 0.97 to 1.17, 9 studies, low quality of evidence)
- Intensive care unit (ICU) mortality (RR 0.81, 95% CI 0.53 to 1.23, 5 studies, low quality of evidence)
- Reintubation (RR 0.92, 95% CI 0.66 to 1.26, 7 studies, low quality evidence)
- ICU and long-term weaning unit (LWU) length of stay (MD -7.08 days, 95% CI -16.26 to 2.1, 2 studies, low quality of evidence)
- Pneumonia (RR 0.67, 95% CI 0.08 to 5.85, 2 studies, low quality of evidence)
But, pressure support was superior to T-tube for successful spontaneous breath trials (RR 1.09, 95% CI 1.02 to 1.17, 4 studies, moderate quality of evidence)
- Evidence from these studies comparing pressure support ventilation with T-tube was low quality
- Pressure support ventilation & T-tube yielded similar effects on weaning success, ICU mortality, reintubation, ICU & LWU length of stay and pneumonia
- PSV was more effective for successful spontaneous breath trials
This investigated the effects of weaning protocols on the total duration of mechanical ventilation, mortality, adverse events, quality of life, weaning duration and length of stay in the intensive care unit and hospital
It included 11 studies with 1971 patients, recruited from a range of intensive care units, including medical, surgical and coronary.
The use of weaning protocols was found to:
- Reduce the duration of mechanical ventilation by 25% (95% confidence interval 9% to 39%, P=0.006; 10 trials)
- Reduce the duration of weaning by 78% (31% to 93%, P=0.009; six trials)
- Reduce the length of stay in intensive care units by 10% (2% to 19%, P=0.02; eight trials)
And at the same time, not adversely affecting either mortality or adverse events such as reintubation, self extubation, tracheostomy and protracted weaning.
The only caveat was the heterogeneity among the studies for duration of mechanical ventilation and duration of weaning, meaning the evidence should be viewed with caution.
- Weaning protocols can result in reduced total duration of mechanical ventilation, weaning duration and length of stay in ITU
So nothing really conclusive.
Pressure support ventilation is probably better for successful spontaneous breath trials. Weaning protocols can reduce the duration of mechanical ventilation and weaning but these findings might not be broadly applicable.
So that clears that up, then!
Written By Dr Richard Pertwee (Clinical Fellow in ITU, Research & Development, FOAMed link fellow)