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This is not a new debate: the wonderful and much-missed Dr John Hinds gave a fantastic pitch seven years ago at a SMACC conference on the continued use of direct laryngoscopy (DL) for pre-hospital intubations.
In 2015 a meta-analysis was published. The authors concluded that video laryngoscopy (VL) did not increase intubation success. We know that intubating a critically unwell patient is a high-stakes procedure. With the golden rule of getting everything optimised to maximise the chances of orotracheal intubation on the first attempt, the use of a video laryngoscope has often been seen as a ‘part of the package’ for increasing intubation success. This paper published in the NEJM researches this further.
As always we recommend you read the full paper yourself (or at the very least the abstract below), to draw your own conclusions. Our thoughts on this really interesting trial follow below.
What did they do?
This was a randomised control trial in the US across seven Emergency Departments and ten Intensive Care Units. They enrolled patients undergoing orotracheal intubation in these settings. The usual groups were excluded such as pregnant patients and prisoners.
Patients were also excluded if the intubating clinician decided that the use of VL or DL was needed for the best patient care. In total 86 patients were excluded for this reason. The supplementary appendix detailed the reasons for this. 76 patients were excluded due to the operator stating VL was indicated with reasons given being “extreme upper airway anatomic difficulty (37), body fluid in the upper airway (12), hyper-angulated blade required (4) and other (23)”. For the patients excluded due to DL being the method of choice, the reasons cited again were “upper airway anatomic difficulty (3), body fluid(2) and other(1) “. As you can see the reasons for either method of laryngoscopy being clinically indicated are very similar in both excluded groups.
I think this is a really important cohort of patients. I would have loved to have seen them included in this trial. It would help me understand in the most difficult group of patients what is going to help me the most for this procedure. So what this trail really looks at is the use of DL vs VL for the intubation of a patient in the ED/ICU, for whom there is no predicted difficulty in endotracheal intubation.
Block randomisation was used. The blocks were “permuted” – this just means that each block was a different size. Within each block, there was still an even number of DL and VL allocations. Randomisation dictated VL or DL for the first attempt, after this everything was the operator’s choice. Importantly the use of a stylet or bougie was seen as standard practice at all sites for the first attempt at intubation.
80 of the patients excluded were due to the operator preferring VL before randomisation. An additional 8 patients were excluded after randomisation in the the DL group. Instead recieving VL on their first attempt laryngoscope. The main reason being cited as a change in patients condition. Does this reveal a bias in the operators? Did they inherently believe that VL is a better intubating technique? Does this therefor make it more likely that DL is set up to fail as the operator believes it won’t be successful Does this belief mean that first attempt at won’t be as good with DL because subconsciously “we know it is going to fail any way”?
The primary outcome was successful intubation on the first attempt. There was a single secondary outcome of severe complications from induction to 2 minutes post intubation.
What were the results?
1417 patients were included in the primary analysis. There were no significant differences in age, sex and median BMI of patients in the two groups. In total 988 (70%) of the intubations occurred in the emergency department. In each group, 45% of the patients were intubated due to altered mental status, with acute respiratory failure accounting for 30% of patients in both groups.
The primary outcome was ‘first pass success’ in the two groups and produced a statistically significant difference, however, it is probably worth just reiterating their definition:
“The primary outcome was successful intubation on the first attempt, defined as the placement of an endotracheal tube in the trachea with a single insertion of a laryngoscope blade into the mouth and either a single insertion of an endotracheal tube into the mouth or a single insertion of a bougie into the mouth followed by a single insertion of an endotracheal tube into the mouth.“
Successful first-attempt intubation in the VL group was 85.1% (600 of the 705 patients) vs 70.8% (504 of the 712 patients) in the DL group. Giving a p value of < 0.001 and a 95% confidence interval of 9.9-18.7.
The reason for first-pass intubation failure was reported by the operator. In the VL group, the most commonly cited reason was an inability to insert the ET tube or bougie (49 patients). Anecdotally it is often said that VL will get you a better view of the cords but it doesn’t make it easier to pass the tube, so it is interesting that these numbers were lower than in the DL group (51 patients). . The results reported in this trial could be due to the use of a bougie or stylet as standard practice.
The most common reason for failure to intubate in the DL group was an inability to view the vocal cords. A 70% first-pass success rate in the DL group is very low and lower than cited in similar studies. This is probably due to a large proportion of the operators having minimal previous experience intubating.
In the secondary outcomes there was no statistically significant difference between the two groups. The 95% CI crossed 0 for all the predefined outcomes. 21.4% (151 of 705 patients) of the VL group had severe complications vs 20.9% (149 of 712 patients) of the DL group, with a 95% CI of -3.9-4.9.
Do any operator characteristics make a difference to first-pass success?
Emergency physicians intubated the majority of patients (70% in each group), with a resident physician being the most common operator (roughly 70% in each group). Data for operator experience were also collected. In total 85% of intubations (1,202) were performed by operators with a log book of 100 or less prior intubations.
Method of previous intubations had also been analysed. Figures in the supplementary appendix reveal that the majority of operators prior to this trial performed greater that 50% of their intubations using VL. With 510 (36%) operators having had over 75% of all their previous intubation experience with video laryngoscope. Is it fair to compare intubation techniques using operators who are very inexperienced with one of the devices? The introduces inherent bias into this trial, all procedures in medicine take time and practice to master, intubation with DL or VL is no different. It is essentially asking an operator to proficiently perform as skill with a new technique that they are not very practiced in and comparing it to a technique they are proficient in and comparing outcomes.
For those physicians who had intubated over 100 patients prior to the trial, first-pass success was 100% regardless of whether they used VL or DL. For those with a log book of fewer than 25 intubations, first-pass success was 80% in the VL group in comparison to 54% in the DL group. What this is saying is, if you have not yet mastered the skill of intubation, you are more likely to succeed with a VL. We could also take from this that DL is a tricker skill to become proficient at. Therefore, when learning the skill of laryngoscopy should DL be used in preference in order to build competency in a supervised environment?
Another aspect not considered in the paper, but very relevant to the rest of the world is the cost involved in providing VL in all circumstances. They remain an expensive item and they are simply not available in many parts of the world.
There are also lots of great reasons for using a VL for teaching and team dynamics. A recent podcast by Scott Weingart on the EMCRIT site explains this really well (well worth a listen). In practice the ability to be able to guide learners on their airway skills using a VL is far superior to DL, and it may be that we see a reduction in the number of learning episodes required to achieve competence by using VL more routinely. This is certainly something Simon Carley advocates (and is also stressed by Scott Weingart who explains it really well). If you’re in a teaching unit then there are good arguments for having VL available that extend beyond simply achieving great FPS rates.
Bottom Line
In this study VL increased first pass success for operators, with the biggest difference seen in those with less experience. Remember that this was a selected cohort of airways with (perhaps) less anticipated difficulty.
References
- Video versus Direct Laryngoscopy for Tracheal Intubation of Critically Ill Adults https://www.nejm.org/doi/pdf/10.1056/NEJMoa2301601
- Simon Carley, “JC: Did Video kill the Laryngoscope star? Here comes the evidence. St.Emlyn’s,” in St.Emlyn’s, July 6, 2013, https://www.stemlynsblog.org/video-laryngoscopy-an-rct-in-trauma-st-emlyns/.
- 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/.
