An LMA, or laryngeal mask airway, is a medical device used to keep your airway open during surgery or in emergencies when you can’t breathe on your own. It sits in the back of your throat rather than going into your windpipe, making it less invasive than a traditional breathing tube. LMAs are one of the most commonly used airway devices in modern anesthesia and emergency medicine.
How an LMA Works
An LMA consists of a short tube attached to a soft, inflatable cuff shaped like a small mask. The device is slid into your mouth and guided down to the back of your throat, where the cuff settles around the opening of your voice box (the larynx). Once in place, the cuff is inflated to create a seal, forming an airtight passage that allows air or anesthetic gases to flow directly into your lungs.
Unlike an endotracheal tube, which passes between the vocal cords and into the windpipe itself, an LMA sits above the vocal cords in the space behind the tongue. This is why it’s sometimes called a “supraglottic” airway device. Because it doesn’t enter the windpipe, it causes less irritation and tissue trauma during placement and removal.
When an LMA Is Used
The most common use for an LMA is during routine surgeries performed under general anesthesia. If the procedure is relatively short, doesn’t involve the chest or abdomen in ways that require high ventilation pressures, and the patient has a low risk of vomiting, an LMA is often the preferred choice over a breathing tube. Examples include minor orthopedic procedures, eye surgeries, and many ear, nose, and throat operations.
LMAs also play a critical role in emergency situations. When someone stops breathing or goes into cardiac arrest, an LMA can be placed quickly to establish an airway, even by providers who don’t have extensive intubation training. It serves as a rescue device when a traditional breathing tube proves difficult or impossible to place, buying time until a more secure airway can be established.
LMA vs. Endotracheal Tube
The key advantage of an LMA over a standard breathing tube is that it’s gentler on the airway. Because it doesn’t pass through the vocal cords, there’s no risk of tracheal injury during placement or removal, less stimulation of the airway, and less invasion of delicate tissue. For patients, this translates to a noticeably more comfortable recovery.
The difference in side effects is significant. In one study comparing the two devices in ear, nose, and throat surgeries, sore throat occurred in about 33% of LMA patients compared to 44% of those who received a breathing tube. Hoarseness was far less common with an LMA (3.5% vs. 24.4%), and post-operative coughing dropped from nearly 13% with a breathing tube to just over 1% with an LMA. Shortness of breath after surgery occurred only in the breathing tube group.
The main disadvantage of an LMA is that it doesn’t protect the lungs as reliably from stomach contents. If a patient vomits while under anesthesia, an endotracheal tube creates a sealed barrier inside the windpipe that prevents fluid from reaching the lungs. An LMA does not offer the same level of protection, so it’s generally not the first choice for patients who haven’t fasted before surgery, are pregnant, or have conditions that increase the risk of vomiting.
Sizing for Different Patients
LMAs come in seven standard sizes based on body weight, ranging from newborns to large adults:
- Size 1: under 5 kg (newborns)
- Size 1.5: 5 to 10 kg (infants)
- Size 2: 10 to 20 kg (small children)
- Size 2.5: 20 to 30 kg (older children)
- Size 3: 30 to 50 kg (small adults or adolescents)
- Size 4: 50 to 70 kg (average adults)
- Size 5: 70 kg and above (larger adults)
First- and Second-Generation Designs
The original LMA design, now called a first-generation device, was a simple tube-and-cuff combination. It worked well for basic airway management but had limitations: it couldn’t handle high ventilation pressures without leaking, and it offered no way to drain stomach contents if they came up during surgery.
Second-generation LMAs addressed both of these problems. The LMA ProSeal, introduced in 1999, added a separate drainage channel that allows any regurgitated stomach fluid to bypass the throat and exit through the device rather than reaching the lungs. It also achieves a tighter seal, with a median sealing pressure of 32 cm of water, enough to support positive-pressure ventilation during surgery. The LMA Supreme, developed in 2007, took this further with a preformed curved shape and a dual-channel design: one channel for air and a separate one for digestive tract access. It creates both a throat seal and a seal against the upper opening of the esophagus, adding another layer of protection against aspiration.
These improvements have expanded the range of procedures and patients for which an LMA is considered safe and effective.
When an LMA Isn’t Appropriate
Several situations make an LMA a poor choice. Patients at high risk for aspiration, including those with full stomachs, severe acid reflux, or delayed stomach emptying, typically need the stronger protection of an endotracheal tube. Airway obstructions caused by tumors or foreign bodies below the voice box can make it difficult or impossible to ventilate through the device.
Obesity presents a particular challenge. Excess tissue in the throat can make it harder to seat the device properly, and the higher ventilation pressures that heavier patients require increase the chance of air leaking around the cuff. For morbidly obese patients, an LMA is generally not used as the primary airway device. An LMA also triggers the gag reflex, so it can only be placed in patients who are unconscious or deeply sedated.
Possible Side Effects
Most side effects from an LMA are mild and short-lived. Sore throat is the most common, affecting roughly one in three patients, though this typically resolves within a day or two. Hoarseness occurs in a small percentage of cases, usually caused by minor irritation or swelling of the vocal cords that clears up within a few days.
Rare but more serious complications can include nerve injury near the voice box, damage to laryngeal cartilage, and vocal cord bruising. These are uncommon and far less frequent than with endotracheal intubation, which is one reason LMAs are preferred when the clinical situation allows it.