Bougie use and first pass success

This week, Cliff Reid highlighted a recent meta-analysis¹ of the use of bougies in tracheal intubation and first-pass success rates. This is something that has been a 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. While I have my own opinions on this, it is always worth reviewing the research to see if my views are evidence-based. We should also remember that bougies are single-use devices, so if there is an argument not to use them routinely, 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.

The Abstract – Effect of Bougie Use on First-Attempt Success in Tracheal Intubations: A Systematic Review and Meta-Analysis¹

The use of a bougie, a flexible endotracheal tube introducer, has been proposed to optimize first- attempt success in emergency department intubations. We aimed to evaluate the available evidence on the association of bougie use in the first attempt and success in tracheal intubations. This was a systematic review and meta-analysis of studies that evaluated first-attempt success between adults intubated with a bougie versus without a bougie (usually with a stylet) in all settings. Manikin and cadaver studies were excluded. A medical librarian searched Ovid Cochrane Central, Ovid Embase, Ovid Medline, Scopus, and Web of Science for randomized controlled trials and comparative observational studies from inception to June 2023.

Study selection and data extraction were done in duplicate by 2 independent reviewers. We conducted a meta-analysis with random-effects models, and we used GRADE to assess the certainty of evidence at the outcome level. We screened a total of 2,699 studies, and 133 were selected for full-text review. A total of 18 studies, including 12 randomized controlled trials, underwent quantitative analysis.

In the meta-analysis of 18 studies (9,151 patients), bougie use was associated with increased first-attempt intubation success (pooled risk ratio [RR] 1.11, 95% confidence interval [CI] 1.06 to 1.17, low certainty evidence). Bougie use was associated with increased first-attempt success across all analyzed subgroups with similar effect estimates, including in emergency intubations (9 studies; 8,070 patients; RR 1.11, 95% CI 1.05 to 1.16, low certainty). The highest point estimate favouring the use of a bougie was in the subgroup of patients with Cormack-Lehane III or IV (5 studies, 585 patients, RR 1.60, 95% CI 1.40 to 1.84, moderate certainty).

In this meta-analysis, the bougie as an aid in the first intubation attempt was associated with increased success. Despite the certainty of evidence being low, these data suggest that a bougie should probably be used first and not as a rescue device in emergency intubations.
von Hellmann R, Fuhr N, Ward A Maia I, Gerberi D, Pedrollo D, Bellolio F, Oliveira J E Silva L. Effect of Bougie Use on First-Attempt Success in Tracheal Intubations: A Systematic Review and Meta-Analysis. Ann Emerg Med. 2024 Feb;83(2):132-144. doi: 10.1016/j.annemergmed.2023.08.484. Epub 2023 Sep 19. PMID: 37725023.

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 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 combine apples and apples rather than apples and oranges (although statistically speaking apples and oranges are actually similar in several ways²). 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 they 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 system3 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 another 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 principal difficulty is sensibly combining results from different trials. 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 is due to heterogeneity (are they really very different) rather than chance. This is commonly done in meta-analyses to check whether it is safe to combine results statistically.

What did they find?

The search strategy found 2699 studies of which 18 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 first pass success 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 video laryngoscope and direct laryngoscopy 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 first pass success 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, video laryngoscope vs. direct laryngoscopy, 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, and hypoxia are more relevant), it does make life easier if the tube goes in the first time. Also, we don’t do a huge number of intubations in the ED/PHEM 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 video laryngoscopy 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 some 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

1.
von Hellmann R, Fuhr N, Ward A. Maia I, et al. Effect of Bougie Use on First-Attempt Success in Tracheal Intubations: A Systematic Review and Meta-Analysis. Annals of Emergency Medicine. Published online February 2024:132-144. doi:10.1016/j.annemergmed.2023.08.484
2.
Barone JE. Comparing apples and oranges: a randomised prospective study. BMJ. Published online December 23, 2000:1569-1570. doi:10.1136/bmj.321.7276.1569