JC: Bougie use in tracheal intubation. St Emlyn’s

This week Cliff Reid highlighted a recent meta-analysis of the use of bougies in tracheal intubation. This is something that has been routine practice in Virchester ED for many years, but we still get colleagues in anaesthesia and ICM who occasionally decline and prefer to use a plain tube. Whilst I have my own personal opinions on this, it is always worth reviewing the research too to see if my views are evidenced based. We should also remember that bougies are single use devices and so if there is an argument not to use them routinely then that would also be worth knowing as we are keen to reduce healthcare waste where we can.

The abstract is below, but as always read the paper for yourself.

What kind of paper is this?

This is a meta-analysis of papers. A meta-analysis takes previously published research and synthesises the results using statistical methods to retrieve, select, and combine results from previous separate but related studies. It’s a subset of a systematic review which looks at the wider body of evidence in that a systematic review does not necessarily use statistical methods to combine the results (so you can have a narrative systematic review without stats).

Tell me about the studies.

In a meta-analysis it’s really important to look at exactly what was studied in terms of the papers. The aim is to statistically combine the results and so we should, as the old saying goes, aim to be combining apples and apples rather than apples and oranges (although statistically speaking apples and oranges are actually similar in several ways). In this study the authors conducted a fairly extensive search to identify papers that looked at adult patients being intubated using a bougie as an intervention compared to usual care. Usual care meant with or without a standard stylet. A bougie was defined as a flexible endotracheal tube introducer with coude tip, and stylet was defined as a semirigid endotracheal tube introducer. If a study looked at plain tube and stylet and bougie, the control group was defined as the stylet option. The authors have published their search strategy as well (good practice) which seems reasonably comprehensive (though did not look at the grey literature).

The research team reviewed the studies and recorded on a standard form.

Tell me about the main outcome.

Interestingly the principal outcome was first pass success, which is usually defined as a single attempt at laryngoscopy leading to tracheal intubation. I say interesting as this is a very common measure of success in intubation studies as it is commonly said that it is associated with patient outcome. However, a recent paper in a high performing system questions this link, and if you stop and think about it, it is probably unlikely in a high performing system that it would make that much difference, though I am interested to hear other view on this. I think that outcomes such as hypoxia, hypotension and cardiac arrest are really what we are interested in following ED/PHEM intubation.

Tell me about the analysis.

In these studies the principle difficulty is how to combine results from different trials sensibly. There are usually different event rates and other biases in the data and judging this can be done statistically and also from the research design/inclusion criteria. It has to make sense statistically and pragmatically. The authors assessed bias using a structured tool from Cochrane (good practice).

The outcome data was analysed using a random effects model which assumes the observed estimates of treatment effect can vary across studies because of real differences in the treatment effect in each study. They can also be affected by chance differences between studies. This is a reasonable approach for this sort of data and studies.

Heterogeneity was analysed using the I-squared statistic which describes how much of the variation across studies that is due to heterogeneity (are they really very different) rather than chance. This is commonly done in meta-analyses as a check as to whether it is safe to combine results statistically.  

What did they find?

The search strategy found 2699 studies of which 18 studies were relevant to the primary outcome question. These studies had over 9100 patients, of which roughly half had been intubated with a bougie. 13 studies were RCTs (two were post hoc analyses of RCTs, so arguably observational)

Overall the FPS rate was higher in the group intubated with a bougie (Pooled RR of 1.11 (95%CI 1.06-1.17)). There was a good mix of VL and DL options. The Pooled RR is the correct way to interpret the data using the mixed model which weights the studies, but if you’re like me it’s tricky to interpret without a baseline and more natural data. So if I butcher their analysis and look at the raw data the FPS rate was 84% for bougie use and 71% for the control. That’s an absolute risk difference of 13% and therefore a number needed to treat of 7.6. That’s quite impressive to be honest, and certainly clinically relevant.

The authors also looked at a range of sub-analyses such as location, VL vs. DL, trial type, airway difficulty etc. and the effect appears to be pretty consistent. The biggest benefit to using a bougie was with higher Cormack-Lehane grades III and IV. Location did not make a huge difference and emergency/non-OR settings, which is most relevant to us also showed a benefit.

So should we always use a bougie?

Although the data is encouraging the authors do point out that the quality of the included trials is not as high as we would like and there is significant heterogeneity. The bougie trial may account for this as it is the only trial that found no benefit, but it’s also quite a large trial and therefore impacts on the analysis.

In the emergency medicine/PHEM setting I think the answer is yes. Although FPS may not be the most important outcome in emergency intubations (I think hypotension, aspiration, hypoxia are more relevant) it does make life easier if the tube goes in first time. Also, we don’t do a huge number of intubations in the ED/PHEM and so having a standard approach which maximises success makes sense. That said, there are times when a stylet is the only thing that will work and we still need to train on using them. I had a case in the summer where I had a tricky intubation in a patient with a small mouth and limited mouth opening. With VL I could see the cords, and went to use the bougie only to discover that the bougies we used at the time turn to a limp piece of spaghetti in the heat and would simply not hold a curve well enough to get through the larynx (we have subsequently changed the brand). A stylet worked really well, and probably works better if you intend to use a hyperangulated blade (and there are those who suggest using a hyperangulated blade for all intubations, something we have not considered here). So if you routinely use a bougie, you won’t be using a stylet as much, and therefore that needs to be something you train with for the day when you have to.

The bottom line

This study reinforces my belief that we should plan on always using a bougie in EM/PHEM intubations.

References and further reading

  1. Effect of Bougie Use on First-Attempt Success in Tracheal Intubations: A Systematic Review and Meta-Analysis. https://pubmed.ncbi.nlm.nih.gov/37725023/
  2. Comparing apples and oranges: a randomised prospective stud BMJ 2000; 321 doi: https://doi.org/10.1136/bmj.321.7276.1569  (Published 23 December 2000)
  3. Intubation first-pass success in a high performing pre-hospital critical care system is not associated with 30-day mortality: a registry study of 4496 intubation attempts. https://pubmed.ncbi.nlm.nih.gov/36411447/
  4. Video Laryngoscopy. https://litfl.com/video-laryngoscopy/
  5. Four Secrets to Video Laryngoscopy https://epmonthly.com/article/four-secrets-to-video-laryngoscopy-/
  6. EMCrit 70 – Airway Management with Rich Levitan https://emcrit.org/emcrit/rich-levitan-airway-lecture/
  7. Simon Carley, “JC: Don’t blame it on the Bougie. St Emlyn’s,” in St.Emlyn’s, May 20, 2018, https://www.stemlynsblog.org/jc-dont-blame-it-on-the-bougie-st-emlyns/.
  8. Laura Howard, “JC – Video vs Direct Laryngoscopy for Tracheal Intubation of Critically Ill Adults,” in St.Emlyn’s, June 25, 2023, https://www.stemlynsblog.org/jc-video-vs-direct-laryngoscopy-for-tracheal-intubation-of-critically-ill-adults/.
  9. Simon Carley, “JC: Macintosh vs. McGrath laryngoscopy in pre-hospital care.,” in St.Emlyn’s, August 14, 2019, https://www.stemlynsblog.org/jc-macintosh-vs-mcgrath-laryngoscopy-in-pre-hospital-care/.
  10. Dan Horner, “The Physiologically Difficult Airway,” in St.Emlyn’s, April 17, 2023, https://www.stemlynsblog.org/the-physiologically-difficult-airway/.
  11. Rick Body, “SASEM: Cutting Edge Evidence-based Airway Management,” in St.Emlyn’s, February 16, 2022, https://www.stemlynsblog.org/sasem-cutting-edge-evidence-based-airway-management/.

Cite this article as: Simon Carley, "JC: Bougie use in tracheal intubation. St Emlyn’s," in St.Emlyn's, April 4, 2024, https://www.stemlynsblog.org/jc-bougie-use-in-tracheal-intubation-st-emlyns/.

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