04 February 2015

In Defense of the Hyperangulated Blade

Let me begin, as is my wont, with a story. Let's say, for the sake of discussion, that I was moonlighting at Janus General Hospital. I had a patient signed out to me by my partner: a young patient with COPD, influenza, and pneumonia. He was on BiPAP and supposedly stable waiting for an ICU bed. Murphy's law being what it is, immediately after my partner left, the patient deteriorated and clearly was going to require intubation. He had all the predictors of being a tough tube, so I made sure to have my back-up plans articulated and ready to go.

My go-to technique for quite a few years is video laryngoscopy (VL) with the hyperangulated blade of the GlideScope. My back-up is direct laryngoscopy (DL) and my ace-in-the-hole is the gum bougie. I'm not a huge fan of fancy tricks like awake intubation (too much work, and I'm lazy) and in any event, this guy was too sick for that. Since this was a daunting airway I made sure to have all the stuff ready to go, including our quick cric tray.

I couldn't get the tube with the GlideScope. While I had a nice view of the larynx, there were frothy secretions welling up through the cords so quickly that between the time I suctioned and tried to place the tube, I lost my view. Faced with crashing sats, I tried to bag him back up, but couldn't ventilate. I got his sats from 50% all the way up to … 75%, and he clearly wasn't going higher. So I had my partner prepping the neck while I went back to the old stand-by, DL, and I was able to snake the bougie in through the foam and successfully passed the tube (much to the disappointment of my partner, who was kind of excited at the prospect of doing a live cric). Here endeth the story.

Now I share this to highlight a couple of points regarding airways. I could make the point regarding the importance of having your back-up plans ready and practiced and not being afraid to progress to a surgical airway, but that point has been made at great length and far more articulately by others. It is a good illustration of the principle, though.

I'm more interested in comparing the relative benefits of VL vs DL and particularly the geometry of the blades.

I admit to being disappointed in seeing the cognoscenti of airway masters coalescing around the position that VL is at best, a necessary evil, and that if it must be tolerated, it should be performed with a standard geometry blade. The C-MAC device, which has a Macintosh-style blade with an attached screen, seems to be the device of choice. (For the record, I have not been paid by either device maker but am more than willing to accept bribes, if any are on the offering.) They make a good argument that the C-MAC is better because it helps develop/preserve the DL skill-set, is its own built-in back-up with no need to change devices, and for attendings allows good supervision of trainees. I agree with all these points.

From my perspective, though, I still favor the GlideScope, which differs from the C-MAC in that it has a hyperangulated blade. (There may well be other brands out there with similar shapes, but I’m not as familiar with them.) And despite the failed airway above (my first ever failed airway in hundreds of cases with this tool), the GlideScope remains my first-line intubating approach in most if not all cases.

A couple of important caveats: I had been intubating with DL for many many years before I ever touched a Glidescope. DL is the ultimate and necessary skill that must be completely mastered before moving on to the hyperangulated blade. For trainees: stick with DL till you've done a few hundred. This is a varsity level device. For occasional intubators it might be a good idea to stick with DL to keep the skills sharp.

I, however, am in none of those categories. I have intubated hundreds if not thousands of people over the years, am highly comfortable with my DL skills, and I continue to intubate pretty frequently. And here’s why I will continue to use my GlideScope until they pry it from my cold, dead hands:

It is a better tool that is easier to use & harder to mess up.

There. I said it. I am, as I said, very lazy, and I will always choose the easy and reliable tool over the dodgy tool which requires a lot of effort to use correctly.

This is why I believe it to be so: when I perform DL, I need to establish a direct line of sight with the larynx. Unfortunately, mother nature thoughtlessly designed the human anatomy so that there are lots of fleshy bits between my eye and your vocal cords. There are lips, teeth, the tongue, the glottis, the salivary glands, and all the redundant fat, muscles and soft tissues of the sublingual space. If I want to establish that direct line of sight, I have to get your head & neck in perfect positions, put the tip of my blade in precisely the right spot, seated in the vallecula, and then lift, sometimes with quite a lot of force, and then I have to hold the blade in place and sort of squint to see way the hell down there for the cords. Blade a little too shallow or too deep? U NO SEE CORDS! Blade slightly off midline with tongue oozing around it? NO CORDS FOR YOU. And the motor skill to lift just the right way is tricky. Rotate the blade and not only do you not see cords, you break teeth. You have to lift up and forward just a bit, and if it’s not quite right, you have to apply cricoid pressure bimanual manipulation to see your target.

This does not look comfortable

I can do it. I’m pretty good at it, still. But there’s a lot of room for error, and sometimes it’s really freaking hard. Even as an experienced intubator, there are times that I am sweating bullets or feeling like I dodged a bullet when I succeed on a tough tube. Because you are fighting the anatomy, and the anatomy is set against you.

But the GlideScope, well, it’s designed so that with no manipulation of the native anatomy, it will drop directly into the necessary position and provide a beautiful view of the larynx. Every damn time. No lifting. No squinting. No fiddling. And if the fleshy bits (excuse the technical anatomic jargon) are still in the way, I don’t care. I can still see my target. It's even forgiving of less than optimal patient positioning. With the GlideScope all the airways are easy, because your tool is designed to work with, not against, the anatomy. That’s the beauty of the hyperangulated blade, and that’s why it has been so widely adopted. You don't need to manipulate the anatomy to see your target, and reducing that step reduces the possibility of error and a failed airway, or at least relieves the cognitive workload of the procedure. It’s rare that I ever have to take a second look, and it seems like every tube slides in effortlessly. And reducing the cognitive workload, reducing provider stress, is not a small benefit when you are dealing with a critically ill patient. If I don’t have to sweat the tube, I can better dedicate myself to management of the patient’s overall condition.

It just fits!

Yes, VL has its limitations. I didn’t say it was perfect. Secretions, blood and gastric contents can confound any intubation, particularly video. Electronics are fallible. Back-ups are necessary and you need to be able to use them. And the use of VL and the hyperangulated blade is a different skill set. Since you can’t see the larynx directly, you need a decent spacial understanding of where you are blindly shoving the blade/tube and the degree of force (or lack thereof) that is safe to use. That only comes with experience and attention to the differences between DL and the hyperangulated blade. It's kind of like tying your shoes in the dark - not exactly tricky, but you do need to be able to visualize what your hands are doing without seeing them directly. But after performing many many intubations with both types of device, I feel that intubations with the GlideScope are easier and less fraught with error.

The airplanes at my flying club are equipped with really cool GPS-linked 3-axis autopilots. But when I was learning to fly, we focused exclusively on basic stick-and-rudder skills, and never touched the autopilot. As I got more advanced, however, we began to use the autopilot more and more. Finally, by the time I was IFR certified, I could take off, turn on the autopilot, fly the entire trip and a linked approach on it, and turn it off just as I began the landing flare.

I see this as highly analogous to the DL-vs-GlideScope debate. You still need your basic airmanship skills. Without those, you die. But the autopilot is a tool which, correctly used, is more reliable than you are at keeping your wings level and frees up your mind and attention for other critical tasks and therefore should be used as much as possible. For those who are more comfortable with DL or VL with a standard geometry blade, I am not saying that there is any evidence-based benefit to GlideScope or that there is clear superiority - keep doing what you're doing if it works for you. This is a personal preference based on my own skill set and how I have found these tools to work. But, contra the growing consensus that VL-with-a-standard geometry-blade is the way to go, I would suggest that outside of the training environment, there are distinct advantages to the GlideScope and would not relegate it to an afterthought among the modalities of airway management.