TRICKS FOR LMA INSERTION
The LMA provides an alternate means to ventilate a patient during surgery — without intubation and while freeing the provider’s hands from having to hold the mask. It provides a more secure airway that makes gastric distention less likely. Since its invention, the LMA has since become quite valuable as a rescue device in situations when intubation may be difficult — even for the inexperienced. Let’s talk about some tips for insertion.
The laryngeal Mask Airway, or LMA, is an extremely useful device for ventilating patients. When I first started in anesthesia, the only way to avoid intubation during anesthesia was to manually assist ventilation with a bag-valve-mask attachment. Cases that went on for hours often resulted in cramped fingers, and sometimes progressively poorer ventilation over time as the hand holding the mask became overly tired. Poor mask seal could potentially cause the stomach to distend, pushing up the diaphragms, limiting tidal volume, and increasing the risk of aspiration.
The LMA was invented by Archie Brain in the 1980s at the London Hospital in Whitechapel. I had the honor of meeting Dr. Brain while in London in 1984 while I was taking a course on providing anesthesia in developing countries, so I got to hear about the LMA while it was still being perfected.
I placed my first LMA in an emergent can’t intubate/can’t ventilate scenario in labor and delivery during a C-section for a morbidly obese patient. Without ever having practiced, I slid the LMA into position and ventilated, avoiding a potential disaster for mother and baby. But I was lucky that it worked perfectly the first time. Sometimes LMAs don’t seat easily, so it’s important to practice ahead of time and to know a few tricks. The main trick to placing an LMA is to take steps to ensure that the tip of the cuff doesn’t fold over or trap the epiglottis.
First, Deflate The Cuff Properly
Prior to placing the LMA, inflate the cushion on the mask and check for leaks or abnormal bulging. Then deflate the cushion with the cuff gently pressed against a flat surface. It’s crucial that the leading edge of the cuff be smooth and wrinkle free to prevent the tip of the deflated cushion from curling. Curling potentially folds the epiglottis down over the glottis during insertion and can prevent a good seal.
Make sure that the cuff rim curves upward, away from the opening. When the flattened cuff is pressed against the palate during insertion, that curve will naturally push it against the palate and help prevent trapping the epiglottis in the cuff bowl.
Lubricate the Posterior LMA Surface
Lubricate the posterior surface of the LMA to allow it to slide easily. Don’t lubricate the surface where the larygneal opening is. Don’t worry if a little lubricant gets on the laryngeal side but a large amount of lubricant here could obstruct the opening or enter the trachea.
Slight Flexion of the Head on the Neck Can Help
If there are no contraindications, flexing the head slightly forward on the neck opens the area behind the larynx, providing space for the LMA cuff to slide down and seat against the upper esophageal sphincter. This position helps provide a better laryngeal seal and also reinforces the sphincter action to prevent reflux and aspiration.
How You Hold the LMA Matters
When inserting the LMA hold it like a pen, with the index finger positioned along the LMA tube so that the fingertip is positioned where the base of the tube meets the junction with the cuff. By pressing down at the junction with the cuff, you can force the tip of the cushion tightly against the palate as it slides inward, preventing the tip from curling under. If you hold the tube of the LMA back near the airway connector, the tip of the cuff will tend to bow and pull away from the palate and posterior pharyngeal wall during insertion- folding its tip and catching the epiglottis.
Open The Mouth As Wide As You Can
Open the patient’s mouth with your left hand and insert the LMA with your right hand. The deflated cuff of the LMA should be directed posteriorly in the midline. The cuff is often quite bulky compared to the width of the unopen mouth so don’t be afraid to open the mouth as wide as you can. Be careful of the teeth. Also be careful of the lips.
This seems obvious, but I have seen many providers tentatively tip the patient’s head back, let gravity open the mouth slightly, and then they try to force a fairly sizable cuff into the narrow gap. This technique usually drags the upper and/or lower lips inward over the top of the teeth. Lips easily get cut on tooth surfaces. Teeth are, after all, designed to cut tissue.
Insert As Far Back as Possible Until It Seats
Insert the LMA as far back as possible, until it seats against the upper esophageal sphincter, overlying the larynx. Pressing backwards and downwards as you insert helps to avoid interference with the epiglottis because this action keeps the cuff tip pressed firmly against the palate. The cuff tip is less likely to curl. Your index finger will often be almost entirely within the mouth. The LMA usually seats with the tip of the mask below the base of the tongue. The dark line on the tube shaft will lie opposite the front teeth.
Occasionally the cuff hangs up on insertion and won’t pass. You can use a tongue blade to pull the back of the tongue forward. You may occasionally need to insert the index finger of your gloved hand into the mouth to straighten the tip of the LMA if it is curling. If you do this, make sure your patient is anesthetized deeply enough not to bite you.
Be Careful With the Tongue
When the tongue gets caught in the LMA cuff bowl during insertion, many providers just keep pushing until the tongue pops forward out of the bowl. The problem with this technique is that it can tear the delicate frenulum, the tissue attachment, underneath the front base of the tongue. This injury tends to be quite painful during the healing process.
Pros and Cons to Leaving the Cuff Partially Inflated
Some people like to leave the cuff partially inflated during insertion. This works reasonably well, but can occasionally cause problems. An inflated cuff is harder to insert into a small mouth. It more easily catches the tongue in the bowl of the cuff. It can also catch on and potentially damage teeth.
When the cuff is inflated at the start, you can’t insert it as deeply. It may therefore fail to seat optimally against the upper esophageal sphincter, leading to potential gastric distension if there is a less than perfect seal around the larynx. Additionally, when the cuff doesn’t seal against the sphincter, you have lost some inherent protection against aspiration.
When inserting the LMA partially inflated, you sometimes need to twist the device sideways to allow the LMA to slip around the side of the tongue before sliding into position behind it.
Watch the LMA Tube and the Neck As You Inflate the Cuff
If the LMA is properly seated, you will usually see the tube rise slightly out of the mouth as you inflate the cuff and you will see the area over the larynx to lift.
On the other hand, if the tube keeps popping out of the mouth by a significant amount, most likely the tip of the tube is not resting low, behind the tongue. If it’s higher in the posterior pharynx you may not be able to obtain a seal and ventilate, and if you can, the LMA may slide out of position when you are least expecting it.
Check Ventilation Immediately
Check ventilation immediately. Just because it looks good, doesn’t mean you have an unobstructed airway. The laryngeal mask airway is a mask, and like any mask must have a good seal around an unobstructed glottic opening in order to to ventilate.
If you can’t ventilate, the most common scenarios are that the either:
- the cuff is not sufficiently inflated to make the seal
- the cuff tip and/or the epiglottis are folded over, obstructing the larynx
- or the cuff is twisted behind the tongue and not making good contact over the larynx
First add air to the cuff. If you still don’t have a good seal, pull the LMA back slightly 1-2 cm with the cuff inflated, look at the line to make sure it’s going in straight, and then reinsert. This action often allows a trapped epiglottis to free itself or allow a folded cuff tip to flip open. You may need to completely remove the device and start over, perhaps considering a different size.
Don’t forget to give your apneic patient a breath or two between insertion attempts.
Consider Having an LMA Available Whenever You Intubate
LMAs have revolutionized anesthetic management as well as provided a superb device for rescue ventilation, both in the hospital as well as in the field. I always have one of the proper size available whenever I provide anesthesia- even if I plan to intubate. It’s one more way you can prepare for that unexpected can’t intubate/can’t ventilate scenario.
In summary, to insert a laryngeal Mask Airway:
- First, Deflate The Cuff Properly
- Lubricate the Posterior LMA Surface
- Slight Flexion of the Head on the Neck Can Help
- How You Hold the LMA Matters
- Open The Mouth As Wide As You Can
- Insert As Far Back as Possible Until It Seats
- Be careful With the Tongue
- Consider Pros and Cons to Leaving the Cuff Partially Inflated
- Watch the LMA Tube and the Neck As You Inflate the Cuff
- Check Ventilation Immediately
- Consider Having an LMA Available Whenever You Intubate
May The Force Be With You