Kovac's Sign
TLDR
Use a 3 blade, regardless of patient size, for video laryngoscopy.
A worse view, in terms of Cormack–Lehane, is better for ETT delivery with VL and actually prevents the situation where an airway appears "too anterior" for the rigid stylette.
Kovac's sign refers to when the cricoid ring is clearly visible and indicates over insertion. The goal to avoid positive Kovac sign is easily accomplished by keeping the vocal cords confined to top 1/3 of display rather than filling it.
The VL3 blade makes this easier to accomplish as the initial view.
To highlight this point: I will pay $50 cash to any resident using the VL3 and VL4 needed during intubation.
TLDR
Use a 3 blade, regardless of patient size, for video laryngoscopy.
A worse view, in terms of Cormack–Lehane, is better for ETT delivery with VL and actually prevents the situation where an airway appears "too anterior" for the rigid stylette.
Kovac's sign refers to when the cricoid ring is clearly visible and indicates over insertion. The goal to avoid positive Kovac sign is easily accomplished by keeping the vocal cords confined to top 1/3 of display rather than filling it.
The VL3 blade makes this easier to accomplish as the initial view.
To highlight this point: I will pay $50 cash to any resident using the VL3 and VL4 needed during intubation.
It was an anterior airway…
While in residency I first started with direct laryngoscopy (DL) until I felt I had it down. Then I progressed to learning video laryngoscopy (VL). My impression was VL would be "easy" in comparison DL and for awhile it sure seemed to be the case.
Then I found a few situations where despite a picture perfect Class 1 view I couldn't seem to get the tube high enough to pass. I was holding the rigid stylette correctly—but still couldn't get it. Incredibly frustrating when it appeared to be the best view possible. My seniors explained it was an "anterior" airway. Had to watch out for those and be prepared.
This happened sporadically to other residents and all kinds of theories were hypothesized. For example, one of my senior residents was convinced they were sending the incorrect rigid stylettes after they had a simliar experience. Others just seemed to think some people had extremely anterior airways. If any of my mentors knew that this wasn't a tough airway issue and rather a knowledge gap I can't say for sure. I know I had never ever heard of Kovac's sign which was the solution
Kovac's sign refers to when the cricoid ring is clearly visible during VL (Pictured below in bottom row).
Kovac's sign indicates over insertion.
In VL, the best grade (by Cormack-Lehane) is actually one of the most dangerous views as it can make the angle of tube delivery so steep (seems too anterior to the proceeduralist) that it is impossible without an adjustment.
If cricoid rings (AKA Kovac's sign) is encountered, the next step is to carefully back out the laryngoscope out of the mouth until a view with no cricoid ring is obtained. A good rule of thumb is to aim for the cords occupy only the top 1/2-1/3 of the display.
Lets talk VL 4 blade.
If you have access to both the VL 3 and VL 4 you may be making the mistake I once did of trying to find a use case for each—similar to the line of thinking when selecting a DL blade. But you shouldn't.
If I'm being honest—I most often use a MAC 4 for every DL intubation for two reasons: 1) Versatility, I can go easy creep it in or in a pinch with a floppy epiglottis I can use it like a Miller. 2) There are definately airways that you simply need a bigger blade than the MAC 3 offers so why risk running into that situation.
The difference that I have found in terms of VL is that both of those reasons are negated. First, there is never a need to use a hyperangulated blade like a Miller and the geometry makes this not even an option if you wanted to. To top it off, you also simply don't encounter airways that need a larger blade ever. Unlike the DL blade you have a camera curving along the blade to look upwards at the airway so even in a long airway there will simply be more room on the screen to manuever and deliver the tube. That's not to mention the improved angle of delivery into the trachea which will be much less acute or anterior-seeming.
The smaller VL 3 blade simply makes it easier to not over insert improving both the angle of rigid stylette for easy insertion and maximizing the real estate on monitor for tube delivery.
I promise you will never regret using the hyperangulated VL 3 exclusively.
When you understand the direct realtionship between depth of insertion and difficulty of tube delivery or "anterior-seemingness"—you have learned the most important concept of VL intubation. If you have the chance to observe others intubate unaware of Kovac's sign or it's signficance you're bound to see one of these beauiful views produce a difficult intubation.
A quick summary:
The hyperangulated VL blades don't work like DL blades and as a result the optimal views differ for each.
If airway too "anterior" during intubation w/ hyperangulated VL blade — you are too deep!
Kovac's sign, or visualization of cricoid ring, should prompt the operator to slowly begin to remove blade back out the mouth.
Try again when the space from epiglottis to posterior trachea fills only the top 1/3 of display.
You can nearly avoid this issue altogether by always using a VL 3 blade rather than a VL 4 blade.
If I'm supervising and you use the VL 3 anyways and find an airway that it's too small for. I'll pay you $50 bucks on the spot.
VL 4 = Trash
Comments
Kovac's Sign
TLDR
Use a 3 blade, regardless of patient size, for video laryngoscopy.
A worse view, in terms of Cormack–Lehane, is better for ETT delivery with VL and actually prevents the situation where an airway appears "too anterior" for the rigid stylette.
Kovac's sign refers to when the cricoid ring is clearly visible and indicates over insertion. The goal to avoid positive Kovac sign is easily accomplished by keeping the vocal cords confined to top 1/3 of display rather than filling it.
The VL3 blade makes this easier to accomplish as the initial view.
To highlight this point: I will pay $50 cash to any resident using the VL3 and VL4 needed during intubation.
It was an anterior airway…
While in residency I first started with direct laryngoscopy (DL) until I felt I had it down. Then I progressed to learning video laryngoscopy (VL). My impression was VL would be "easy" in comparison DL and for awhile it sure seemed to be the case.
Then I found a few situations where despite a picture perfect Class 1 view I couldn't seem to get the tube high enough to pass. I was holding the rigid stylette correctly—but still couldn't get it. Incredibly frustrating when it appeared to be the best view possible. My seniors explained it was an "anterior" airway. Had to watch out for those and be prepared.
This happened sporadically to other residents and all kinds of theories were hypothesized. For example, one of my senior residents was convinced they were sending the incorrect rigid stylettes after they had a simliar experience. Others just seemed to think some people had extremely anterior airways. If any of my mentors knew that this wasn't a tough airway issue and rather a knowledge gap I can't say for sure. I know I had never ever heard of Kovac's sign which was the solution
Kovac's sign refers to when the cricoid ring is clearly visible during VL (Pictured below in bottom row).
Kovac's sign indicates over insertion.
In VL, the best grade (by Cormack-Lehane) is actually one of the most dangerous views as it can make the angle of tube delivery so steep (seems too anterior to the proceeduralist) that it is impossible without an adjustment.
If cricoid rings (AKA Kovac's sign) is encountered, the next step is to carefully back out the laryngoscope out of the mouth until a view with no cricoid ring is obtained. A good rule of thumb is to aim for the cords occupy only the top 1/2-1/3 of the display.
Lets talk VL 4 blade.
If you have access to both the VL 3 and VL 4 you may be making the mistake I once did of trying to find a use case for each—similar to the line of thinking when selecting a DL blade. But you shouldn't.
If I'm being honest—I most often use a MAC 4 for every DL intubation for two reasons: 1) Versatility, I can go easy creep it in or in a pinch with a floppy epiglottis I can use it like a Miller. 2) There are definately airways that you simply need a bigger blade than the MAC 3 offers so why risk running into that situation.
The difference that I have found in terms of VL is that both of those reasons are negated. First, there is never a need to use a hyperangulated blade like a Miller and the geometry makes this not even an option if you wanted to. To top it off, you also simply don't encounter airways that need a larger blade ever. Unlike the DL blade you have a camera curving along the blade to look upwards at the airway so even in a long airway there will simply be more room on the screen to manuever and deliver the tube. That's not to mention the improved angle of delivery into the trachea which will be much less acute or anterior-seeming.
The smaller VL 3 blade simply makes it easier to not over insert improving both the angle of rigid stylette for easy insertion and maximizing the real estate on monitor for tube delivery.
I promise you will never regret using the hyperangulated VL 3 exclusively.
When you understand the direct realtionship between depth of insertion and difficulty of tube delivery or "anterior-seemingness"—you have learned the most important concept of VL intubation. If you have the chance to observe others intubate unaware of Kovac's sign or it's signficance you're bound to see one of these beauiful views produce a difficult intubation.
A quick summary:
The hyperangulated VL blades don't work like DL blades and as a result the optimal views differ for each.
If airway too "anterior" during intubation w/ hyperangulated VL blade — you are too deep!
Kovac's sign, or visualization of cricoid ring, should prompt the operator to slowly begin to remove blade back out the mouth.
Try again when the space from epiglottis to posterior trachea fills only the top 1/3 of display.
You can nearly avoid this issue altogether by always using a VL 3 blade rather than a VL 4 blade.
If I'm supervising and you use the VL 3 anyways and find an airway that it's too small for. I'll pay you $50 bucks on the spot.
VL 4 = Trash
Comments