Use of straight laryngoscopy blades differs from curved blades. Intubation by direct laryngoscopy depends on using the laryngoscope blade to give you a clear field of view of the larynx by shifting the tongue and other pharyngeal structures out of the way. As you might imagine, the patient’s anatomy, pathology, or position can sometimes make this visualization difficult. Laryngoscopy blades come in different shapes to help manage these various situations.
My padawan students often struggle with using a straight blade, such as the Miller blade, as opposed to a curved blade, such as the MacIntosh blade. Let’s talk today about how and then when to use a straight blade.
Laryngoscopy using the straight blade showing the larynx.
Insert the Blade to the Right, Slide tongue to the Left
You insert a straight laryngoscopy blade to the right side of the mouth and then slide the tongue to the left as you lift. The final position places the blade slightly left of center of the mouth and with the tongue compressed and pushed out of the field of view toward the left. You deliberately place the tip of the straight blade underneath the epiglottis. Lifting the straight blade directly lifts the epiglottis upward and allows you to see a clear path into the larynx.
Picture the Sword Swallower
Picture the position of the head and neck when a sword swallower swallows the sword. To get that long blade down the esophagus without puncturing anything vital, there must be a fairly straight path from the mouth opening down the throat. This is similar to what you are doing with a straight laryngoscope blade insertion. You must tilt the head back during insertion to make this work. As you might imagine, it might be harder to use a straight laryngoscopy blade if the patient can’t tilt their head back.
Insert the straight laryngoscopy blade into the mouth and advance until the tip is beyond the back of the tongue.
Tilt the head into extension and lift the epiglottis with the tip of the blade.
Be Precise With Placement
Placement of the straight laryngoscopy blade must be more precise because this blade is narrower than a curved blade. If you don’t slide the blade far enough to the left, you often won’t leave yourself enough room to pass the endotracheal tube. The wider curved blade is a bit more forgiving.
Control the Tongue
The tongue will tend to slide underneath the narrow blade if you don’t control it. With loss of control, you not only lose your view, you risk damaging teeth. One predisposition to losing tongue control is failure to lift the jaw high enough. The weight of the jaw on the blade pins the tongue into position. Because padawans fear hurting their patients they often don’t lift, allowing the tongue to slide. You must purposefully lift upward and let the weight of the head help you.
Don’t Be Afraid: Lift, Lift, Lift
The other reason to lift is to get the best view of the larynx. Intubation is a fairly physical activity and you may need to suspend the head from the blade in certain situations. However, be very careful to protect the teeth as you lift. Think of that sword swallower position again.
Let’s look at the final blade position during the lift and compare it to the curved blade.
Difference in final position between straight and curved blades. Curved blade on left places tip in vallecula. Straight laryngoscope blade on right lifts epiglottis directly.
Watch The Teeth!
That blade angle could bring you perilously close to breaking those front teeth unless you lift the blade upward rather than tilt the blade backward. Don’t use the teeth as a lever.
So let’s summarize the key tips for using a straight laryngoscope blade:
- Insert the blade to the right, slide the tongue to the left
- Think of the sword swallower: tilt the head during insertion to bring larynx into view
- Be precise with placement: the tip goes underneath the epiglottis
- Control the tongue: let the blade pin it in place with the weight of the head
- Don’t be afraid: lift, lift, lift
- Watch those teeth: don’t use the blade as a lever
Intubation using the straight laryngoscope blade.
When to Use a Straight Laryngoscope Blade
A curved blade depends on displacing the soft tissue at the base of the tongue forward in order to bring the larynx into view. In contrast, the straight blade depends on lifting the epiglottis and flattening the tongue. Therefore, a straight blade can be more helpful in situations where there is little room to displace the tongue and attached tissues forward such as patients with:
- short, thick necks,
- larynxes positioned higher in the neck,
- morbid obesity
- big tongue
- larynx fixed from scar, trauma, edema, or mass effect
Practice with both blades on the easy patients. That way, when a difficult intubation comes along, you control the situation rather than letting the situation control to you.
May the force be with you.
Christine E. Whitten MD
author Anyone Can Intubate: A Step By Step Guide, 5th Edition &
Pediatric Airway Management: A Step-by-Step Guide
This really cleared up the technique for me on the 2 types of blades. I’ve been looking for weeks for a proper visualization representation and description. You’re the first one to be able to describe it clearly, so thank you!
You are so welcome. Thanks
Thanks for doing this.
Would you mind doing same for a Mac blade?
I’d be happy to. Thanks for the suggestion
Thanks you for asking. I will definitely work on that.
Hi! Great topic. The other day, discussing intubation with residents, we could not figure out why is it that on the mach blade you dont lift the epyglotis, and in the straight Miller you do lift it. What is your opinion on that matter? Is there any place for the Miller blade in adult intubation? Thank you!
So sorry I’m answering this late, I just found a few messages I hadn’t replied to. i apologize.
Curved blades depend on displacing the tongue and soft tissue forward to lift the epiglottis. If you can’t displace the tongue forward, then you won’t lift the epiglottis and you won’t be able to see the larynx. However, you can lift the epiglottis with a curved blade and if the blade happens to grab the epiglottis, then that’s how I lift it.
Straight blades are very helpful in situations where there is little room to displace the tongue and attached tissues forward. Examples include:
young children (larynx higher in the neck)
adult patients with short chins, short necks, larynxes higher in the neck, large tongues, obesity (especially with double chins), larynxes fixed from scar, trauma, or mass effect.
However, to be able to see the larynx with a straight blade you have to be able to extend the head backward. If your patient can’t tilt his head back, a straight blade will be more difficult. Here a curved blade might be better.
Hi Dr Whitten and thank you so much for this blog post. I’ve been learning to use the straight blades recently and have been reading around this topics. And your description and illustration are by far the easiest to understand.
May I just ask one question: people talk about “paraglossal” vs “retromolar” approaches when they talk about straight blades. Whilst I’m now loving the paraglossal approach after some practice — which I believe is the technique detailed in this post — I’ve never been able to wrap my head around the “retromolar” approach. Do you have any experience on it? And would it be possible if you can please explain how it is performed? Many thanks!
So sorry for the delay in responding, there was a death in the family. The retromolar approach involves inserting the straight blade the retromolar space (the space behind the molars). Basically you are inserting the straight blade far to the right side of the mouth, aiming the tip behind the right molars.
It can be helpful in patients with limited mouth opening for any reason, or when the larynx is hard to see. However, not every patient has enough space behind the molars. Take care to not damage teeth. You will also find that you will need your assistant to distract the cheek tissue fairly aggressively in order to allow you to see. I did not use it often.