Comparison of direct and indirect epiglottis lifting techniques using the McGRATH TM MAC video laryngoscope on the incidence of intubation-related complications: a randomized controlled trial
This multicenter randomized controlled trial found that while direct epiglottis lifting with the McGRATH™ MAC video laryngoscope reduced the need for external laryngeal manipulation, it did not significantly alter the overall incidence of intubation-related complications compared to indirect lifting, though it was associated with a specific risk of epiglottal displacement.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Every time a patient undergoes general anesthesia, a doctor must secure a breathing tube into their windpipe. To do this, they need a clear view of the vocal cords, which sit hidden behind a small, leaf-shaped flap of cartilage called the epiglottis. For decades, doctors used a straight metal blade to lift this flap out of the way, a technique that required aligning the mouth, throat, and windpipe into a perfect straight line. Today, many doctors use video laryngoscopes, devices with a small camera at the tip that lets them see the vocal cords on a screen without needing that perfect alignment. This technology has made intubation safer and more successful for most patients. However, even with a camera, the doctor still has to decide how to lift that stubborn epiglottis flap. They can either hook the blade under the flap and pull it up directly, or they can place the blade in the small valley just in front of the flap and use that leverage to lift it indirectly. While the direct method is known to give a clearer view of the vocal cords, no one knew for sure if that extra visibility came with a hidden cost, such as more injury to the throat or teeth.
A team of researchers at two medical universities in Japan set out to answer this question by watching what happens when doctors use these two different lifting methods. They recruited nearly a thousand adult patients scheduled for elective surgery who needed a breathing tube. The patients were randomly assigned to one of two groups: one where the doctor used the direct lifting technique, placing the blade under the epiglottis, and another where the doctor used the indirect technique, placing the blade in the valley in front of it. The doctors performing the procedures ranged from experienced board-certified anesthesiologists to residents who were still in training, ensuring the results would reflect real-world practice. The researchers then watched closely for any signs of trouble, looking for a wide range of potential complications, including a sore throat, hoarseness, low oxygen levels during the procedure, damage to teeth, or the epiglottis itself getting folded over or displaced.
The study found that, overall, the two methods were remarkably similar in terms of safety. When the researchers combined all the possible complications into a single measure, about 43 percent of patients in the direct lifting group experienced at least one issue, compared to 42 percent in the indirect group. This difference was so small that it could easily be due to chance rather than a real effect of the technique. The most common problems in both groups were mild sore throats and hoarseness, which occurred in roughly a quarter of all patients regardless of the method used. Serious issues like damage to teeth or low oxygen levels were very rare and happened at the same low rate in both groups. This suggests that for the average patient, neither method is significantly more dangerous than the other when it comes to the overall risk of injury.
However, the study did uncover one distinct difference between the two approaches. The direct lifting technique, where the blade goes under the epiglottis, made it easier for doctors to see the vocal cords, which meant they needed to apply external pressure to the patient's neck to help guide the tube about half as often as they did with the indirect method. But this advantage came with a specific trade-off: the epiglottis got folded over or displaced in about 4.5 percent of the direct lifting cases, while it never happened in the indirect group. In the indirect group, the flap stayed in its normal position. When the flap did fold over in the direct group, the doctors were able to see it on the video screen, reposition the blade, and fix the problem before inserting the tube. The researchers noted that while this displacement is a unique risk of the direct method, it is something a careful doctor can spot and correct immediately.
The results held true across the board, whether the doctor performing the intubation was a senior expert or a trainee. The study did not find that one technique was universally better or worse for every type of doctor. The main takeaway is that both methods are safe for routine use, but they offer different experiences for the doctor. The direct method offers a clearer view and less need for external neck manipulation, but it requires the doctor to be vigilant about the position of the epiglottis to ensure it does not fold over. The indirect method avoids that specific folding risk but may require more external help to get a good view. Ultimately, the choice between the two comes down to the doctor's preference and skill, as neither approach appears to cause significantly more harm to the patient than the other.
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