Many years ago our operating room administration decided that the bath towels we were using to position the head for intubation were a potential danger for shedding lint. So one night, in their infinite wisdom, the towels were all summarily confiscated and when we arrived the next morning there wasn’t a single towel to be found, ever again. It may be an exaggeration to say that chaos ensued, but it felt like that.
The reason this event is so memorable is that for the next several days our anesthesia providers had trouble intubating. We likened it to an expert golfer who, when suddenly faced with a new set of golf clubs of slightly different weight and length, suddenly has to relearn the game. It made us realize that how we position the head in the sniffing position often sets us up for either an easy or for a more difficult intubation if you don’t realize what’s happening during the positioning.
Optimizing Head Position
Let’s start by reviewing the goals of positioning. To orally intubate you need to bring the path from the incisor teeth to the larynx into a straight line. This path has three axes:
axis of the cavity of the mouth (oral axis)
- axis of the cavity of the pharynx (pharyngeal axis)
- axis of the larynx and trachea (laryngeal axis)
The angle of the axis of the mouth to the larynx is 90°. That of the pharynx to the trachea is obtuse. Aligning them is merely a matter of applied mechanics. You make this alignment by moving the patient’s head and neck into optimal position and then using the laryngoscope blade to make the final adjustment. (Note: Here I am talking about patients without risk of cervical spinal cord injury. Other techniques can be used if you shouldn’t move the patient’s head and neck.) You can intubate in any position, however, placing the patient’s head at the level of the lower tip of your breastbone, or xyphoid process, gives the best mechanical advantage.
To get the average, non-obese adult patient’s head into this position, we raise the head about 10 cm (4 inches) off the bed by placing a folded sheet or other object under the head. Leave the shoulders on the bed.
This positioning aligns the pharyngeal and laryngeal axes. The cervical spine is now straight and the patient is in the so-called “sniffing position.” Picture how someone out of breath holds her head: forward and tilted slightly back. We automatically straighten the airway to minimize resistance when we want to move a lot of air easily. Another analogy is picturing the sword swallower. In order to pass the sword without injury down the esophagus, which is parallel to the trachea, everything has to be in as straight a line as possible.
The sniffing position typically places the ear canal level with the anterior shoulder. Once you head is optimally positioned, tilt the head into extension with your right hand to bring all the axes into alignment.
Different Ways to Position The Head
You can always use personal strength to lift the head into the air and into the optimal position, and many times in the emergency situation, such as in the field, you may not have much choice. However, it can be very tiring, especially if the intubation attempt is prolonged and your upper body strength is not well developed. It’s easy to loose focus, pivot your wrist and damage teeth. To avoid the need to lift so high, we typically position the head to bring the axes into alignment without having to lift the head off the bed.
The most common things used to position the head are folded towels, folded sheets, rolled blankets, foam “donuts”, foam headrests, and a helper’s hand. Does it matter what you use? As my anesthesia department discovered that morning so long ago, the density and texture of what you use actually can affect technique.
Pros: 1-2 folded towels usually optimal. Soft and easily malleable, allowing quick alteration in shape (mounding or flattening) as needed. Easy to tilt the patient head backward even if the stack of towels is too high because they slide and mold to the shape you need quickly, without having to pull a towel out of the stack.
Cons: Allegedly may shed some minimal lint (potential Operating Room issue).
Pros: Easily available in most settings. Soft and somewhat malleable but not quite as much as towels. Can usually tilt head backward even if too high by shoving the top sheet inward toward the patients shoulders. No lint.
Cons: Not quite as malleable as towels but pretty good. You need a lot more of them because they are thinner which may create a linen supply issue.
Pros: Don’t need as many to lift the head because they are thicker.
Cons: Very dense. Hard to change shape if the head position is not optimal. If too high may prevent tilting the head back and impede opening mouth. They also tend to be quite firm and if the patient is going to lie on them for hours, such as in an OR, you should periodically move the head to prevent pressure spots.
Foam Donut and Foam Headrest (e.g. Shea type headrest)
Pros: Designed to hold the head steady for procedures so head won’t “roll”. Soft cushion which can then be used during the anesthetic to protect the head from pressure points.
Cons: Makes it harder to tilt the head back. It’s also easy to be fooled into thinking head is optimally positioned when it isn’t. The back of head is in the donut hole, often flat on the surface — however from the side the head looks like it is lifted into the sniffing position. . If you are going to use a foam headrest/donut check to see if the patient’s ear canal is level with the sternal notch. If it’s not you may need to add something underneath to lift it higher. Then make sure the patient can still tilt their head back. If they can’t, you won’t be able to see the larynx easily.
Pros: You usually have one immediately available.
Cons: It’s easy for your assistant to accidentally move the head during intubation, which is dangerous for teeth. The most secure way is to have your assistant place his/her closed fist under the head and rest it on the surface (Fig 5-3). If your assistant is providing physical then lift make sure you’re both communicating well. Teeth can be broken if the assistant suddenly shifts the head at the wrong moment.
The Linen Ramp
If the patient is obese, the anterior-posterior width of his/her chest wall and breast tissue can interfere with laryngoscopy and visualization. Building a shallow ramp by placing folded linen under the shoulders, with the goal of aligning the ear canal with the sternal chest, often improves your ability to open the mouth and see the larynx.
Ramping With The OR Table
You can, in fact, use the standard OR table to ramp the patient as long as the head rest is on and the patient is positioned on the bed with his back on the back section (as opposed to being rotated on the bed with his back on the leg section).Raise the back section about 20-30 degrees and then tilt the head section back, checking to make sure that the ear canal and the sternal notch are aligned.
If the patient is rotated on the bed you can accomplish the same effect by placing the bed in reverse trendelburg and tilting the head back. The disadvantage of this maneuver is that there is a greater risk of hypotension with the legs down.
The nice thing about using the bed to create the ramp for the OR is:
- You can adjust the degree of ramp easily during the intubation if it’s not optimal
- You don’t have to remove the linen that you used to build the ramp after the patient is intubated if it interferes with surgical positoning. Removing a sizable linen ramp from underneath an anesthetized morbidly obese patient can be difficult.
- You can put the patient back into the ramped position at the end of the case for extubation, thereby being better prepared to reintubate should the patient fail the extubation attempt
- You don’t need a lot of linen to build the ramp
There are many different ways to attain the “sniffing position” for an intubation. Each one has advantages and disadvantages. However, if you don’t take those differences into account, your intubation can be a lot more difficult than it needs to be.