TRICKS FOR LMA INSERTION

This article covers the Laryngeal Mask Airway (LMA) insertion technique, focusing on preventing cuff tip folding or trapping the epiglottis. The LMA allows patient ventilation during surgery without intubation and keeps the provider’s hands free. It provides a secure airway with less risk of gastric distention and is an effective rescue device when intubation is challenging. Here are tips for LMA insertion.

The laryngeal Mask Airway, or LMA, is an extremely useful device for ventilating patients. When I began practising anesthesia, manual bag-valve-mask ventilation was the only alternative to intubation. Long procedures often led to hand fatigue, resulting in a weaker mask seal, reduced ventilation, stomach distension, and an increased aspiration risk.

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. To place an LMA correctly, make sure the cuff tip doesn’t fold or catch the epiglottis.

First, Deflate The Cuff Properly

Prior to LMA insertion, 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. Otherwise the tip of the deflated cushion will curl. 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. Pressing the flattened cuff against the palate during insertion helps guide it and prevents the epiglottis from being trapped 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. However, a large amount of lubricant here could obstruct the opening or enter the trachea.

Slight Flexion of the Head on the Neck Can Help

Provided there are no contraindications, slight flexion of the head on the neck facilitates opening the space posterior to the larynx. This maneuver enables the LMA cuff to advance and position securely 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

Hold the LMA like a pen, placing your index finger along the tube at the junction with the cuff. Pressing here keeps the tip firm against the palate during insertion, preventing it from curling under. Holding the tube near the airway connector can cause the cuff tip to fold, pull away from the palate, and catch 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. Don’t be afraid to open the mouth as wide as you can. Be careful of the teeth. Also be careful of the lips.

Providers often tilt the patient’s head back and use gravity to open the mouth slightly, forcing a large cuff into a narrow gap. This method can pull the lips over the teeth, leading to cuts. Remember, teeth are sharp and 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. Inserting with backward and downward pressure keeps the cuff tip against the palate, preventing interference with the epiglottis. 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. Sometimes, you may need to insert your gloved index finger inside the mouth to straighten the LMA tip if it curls. If you do this, make sure your patient is anesthetized deeply enough not to bite you.

Be Careful With  the Tongue

If the tongue gets stuck in the LMA cuff bowl during insertion, forcing it forward can tear the delicate frenulum beneath 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.

If the cuff is inflated during initial placement, insertion depth may be reduced. This can result in poor positioning against the upper esophageal sphincter and potentially an imperfect seal around the larynx. This increases the risk of gastric distension. Furthermore, inadequate sealing at the sphincter decreases the protective barrier against aspiration.

When inserting a partially inflated LMA, it may help to twist it sideways to guide it past the tongue and into position.

Watch the LMA Tube and the Neck As You Inflate the Cuff

When the LMA is positioned correctly, the tube typically rises a bit from the mouth as you inflate the cuff, and the region over the larynx will visibly lift.

If the tube repeatedly slips out of the mouth, the tip is likely too high in the posterior pharynx instead of low behind the tongue. This can prevent sealing and ventilation, or cause the LMA to dislodge unexpectedly.

Check Ventilation Immediately

After LMA insertion, check ventilation immediately. Just because it looks good, doesn’t mean you have an unobstructed airway. The laryngeal mask airway is a mask. 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 a good seal is not achieved, withdraw the LMA 1-2 cm with the cuff inflated, check alignment, and 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

Christine E. Whitten MD, author:

Anyone Can Intubate: A Step-by-Step Guide, 5th Edition
Pediatric Airway Management: A Step-by-Step Guide
Basic Airway Management: A Step-by-Step Guide