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.
Insert the Blade to the Right, Slide tongue to the Left
You insert a straight 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 blade if the patient can’t tilt their head back.
Be Precise With Placement
Placement of the straight 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 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.
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 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
When to Use a Straight 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.