Mike: Hello, I'm Mike Clarke, podcast editor for the Cochrane Library. Anaesthetists use a variety of techniques to insert a breathing tube into a patient before an operation. These include using a rigid indirect videolaryngoscope and the Cochrane review comparing this with the traditional direct laryngoscope was updated in April 2022. In this podcast, two of the authors, Jan Hansel and Andy Rogers, who are from Manchester University NHS Foundation Trust and Royal United Hospitals Bath NHS Trust in the UK, chatted about the procedures.

Jan: Hi Andy, what sort of kit did you use for your last anaesthetic?

Andy: A 25 Gauge Sprotte, why?

Jan: Hah, okay sorry, I meant for the last patient you intubated.

Andy: Oh, I see. I used a Macintosh-style videolaryngoscope with a size 3 blade. 

Jan: So, were you expecting it to be a difficult airway?

Andy: No, not really. I just tend to go for the videolaryngoscope first these days.

Jan: See that's interesting. Ever since we did our review, I've also started using videolaryngoscope first, so long as it's readily available. And I used to be an avid direct laryngoscope user.

Andy: I agree. The evidence does seem to be quite overwhelming, doesn't it and there's a lot to remember.

Jan: Yes, we looked at all studies comparing videolaryngoscope to direct laryngoscope in adults undergoing tracheal intubation, in any setting. And we identified a whopping 222 studies that we ended up including, with just north of 24,000 participants.

Andy: Remind me, were the studies any good. What about the risk of bias?

Jan: Well, most studies had a high risk of bias in at least one domain, mostly owing to the inability to blind intubators to the device allocation.

Andy: And what about the outcomes?

Jan: We focused on failed intubation, hypoxaemia, successful first attempt and oesophageal intubation as the key outcomes. We also looked at quality of glottic view, time required for intubation, mortality and a few more. And we also went beyond just experienced anaesthetists inserting the breathing tube, didn't we?

Andy: Yes, we included some studies that were done in a prehospital setting, emergency department or critical care. And the experience of the people inserting the tube varied from complete novices to clinicians highly experienced with both direct and videolaryngoscopy techniques.

Jan: So, there was a fair bit of variety in terms of skill mix. From what I remember, 21 of the studies were conducted outside of the theatre setting. And a variety of devices were used...

Andy: Yes, we divided the devices into three categories: Macintosh-style, hyperangulated and channelled, with the insertion technique being markedly different for each of these. For example, hyperangulated videolaryngoscopes have a more acutely angled tip which normally requires the use of a preformed stylet, whereas the channelled devices have a working side channel through which the tube is advanced. Macintosh-style ones, on the other hand, are based on the original Mac blade.

Jan: Yes, that's true and we found moderate-certainty evidence that all three designs probably reduce the rates of failed intubation, increase the rates of success on the first attempt and improve our glottic views, when compared to direct laryngoscopes. Hyperangulated devices seem to reduce the rates of oesophageal intubation and are particularly helpful in reducing failure in individuals with a predicted, simulated or known difficult airway.

Andy: So overall, videolaryngoscopes seem to outperform direct laryngoscopes in most domains, don't they?

Jan: I would say so and, if anyone listening to us wants to read more about this, they can get the full review by going to the web address cochranelibrary.com and running a search for 'videolaryngoscopy versus direct laryngoscopy in adults'.