Monday, 29 February 2016

Apneic Oxygenation During Intubation; Curbing the Enthusiasm.

The current enthusiasm for apnoeic oxygenation has been based more on physiologic plausibility & wishful thinking rather than any real science from good quality RCT’s.

One always needs to be a bit skeptical of physiologic plausibility. Of course it is an essential ingredient for assessing causality, but it is far from the only requirement. To be sure, I would imagine that one could think of a physiologic reason why we could fart ourselves to the moon.

Now we have the largest RCT investigating the efficacy of apnoeic oxygenation. A whole 150 patients.

Inclusion criteria were adults requiring intubation in a single medical ICU in Nashville, Tennessee. The intubator was a “pulmonary and critical care medicine fellow.” (This is probably about a PGY-4 doctor)

There were some exclusion criteria that probably meant that some of the sicker patients were not enrolled.

The study protocol was pragmatic and simulated “real world” ICU practice.  Therefore it governed only the provision of supplemental oxygen during apnoea. All other decisions about medications, devices, etc. were made by the clinical team.

Both groups could get pre-oxygenation. The patients randomized to apnoeic oxygenation got a high-flow nasal cannula set to 15L/min flow of 100% oxygen before induction and kept in place until the intubation was complete. The control group received no nasal cannula oxygen.

The primary outcome was the lowest pulse oximetry reading between induction and 2 minutes after successful intubation. Some might argue this is not the most patient oriented outcome but at least it is practical and easy to measure.

Results? There was no statistical difference between the two groups. The median lowest sat in the apnoeic oxygenation group was 92% vs. 90% (95% CI for the difference -1.6%-7.4%) in the control arm. Just for interest, they had only 2/3 success in first pass intubation rate.

This study was powered to have an 80% probability of detecting a 5% difference in the primary outcome if one truly existed in the population. All of the trends favoured the apnoeic oxygenation group and it is possible that the study was underpowered. However, one might question if such smaller differences are clinically meaningful. Probably not.

Limitations were several, but overall this was a well conducted study. Consider lack of blinding, single centre study, perhaps lack of intubator experience, issues of external validity, disease oriented outcome measure and some others.

So what are we to conclude? I don’t think this study is going to change anyone’s minds. True believers will still believe. But it certainly emphasizes the lack of good quality evidence to support the practice of apnoeic oxygenation. I personally don’t bother with it. But at the same time we should not have polarized views until better quality evidence provides us with some answers.


Covering:

Semier MW, Janz DR, Lentz RJ, et al. Randomized Trial of Apneic Oxygenation during Endotracheal Intubation of the Critically Ill. Am J Respir Crit Care Med 2016;193:273-80.




No comments:

Post a comment