What Is a King Airway and How Is It Used in EMS?

The King airway is a supraglottic airway device used primarily by emergency medical services to establish a breathing passage without the complexity of inserting a tube directly into the trachea. It sits in the esophagus and seals off the throat with inflatable cuffs, allowing ventilation through an opening positioned over the larynx. Since its introduction in the early 2000s, the King airway has become one of the most widely used alternatives to traditional endotracheal intubation in prehospital emergency care, though recent head-to-head data against newer competitors has complicated its standing.

How the Device Works

The King airway is a latex-free silicone tube designed to be inserted blindly into the mouth and advanced until it seats in the upper esophagus. It has two inflatable cuffs: a larger one near the base of the tongue that seals the oropharynx, and a smaller one at the tip that seals the esophagus below the glottis. Between the two cuffs, ventilation holes sit directly over the laryngeal inlet, creating a channel for air to reach the lungs. A single pilot balloon inflates both cuffs simultaneously with a syringe, which simplifies the process compared to devices requiring multiple inflation steps.

In a controlled hospital study of 50 adult patients under general anesthesia, a patent airway was achieved in every patient. The device was placed on the first attempt about 86% of the time, with nearly all remaining cases succeeding on a second or third try. Placement took less than five seconds in 90% of cases, and the seal pressures averaged around 31 cm of water, which is strong enough for most routine ventilation scenarios.¹ The high seal pressures are one of the King airway’s distinguishing features. A pediatric randomized trial found that the LTS-D variant generated seal pressures around 38 cm of water, considerably higher than those produced by the i-gel device in the same study.²

Device Variants

The King airway is not a single product but a family of related devices. The original King LT was a reusable model designed for operating room use. The King LTS-D, which added a suction channel for gastric decompression, became the dominant version in emergency medicine. That suction port matters because unconscious patients frequently vomit, and the ability to pass a tube through the device to drain stomach contents reduces aspiration risk. A small paramedic study found 100% insertion success with the LTS-D, with over 90% of placements succeeding on the first attempt.³

Sizing is based on the patient’s height rather than weight, which simplifies selection during emergencies. The devices come in sizes ranging from pediatric (for patients under 35 inches tall) up to adult sizes for patients over six feet. Getting the size wrong can cause problems. A case report documented a deep 5 cm perforation of the hypopharynx in a patient whose laryngeal tube bent and was forced into the piriform recess, a pocket-like structure on either side of the larynx. While tongue swelling and minor trauma are recognized complications, this type of perforation is rare but highlights what can go wrong with poor sizing or forceful insertion.⁴

Why EMS Agencies Adopted It So Widely

Endotracheal intubation, where a tube passes through the vocal cords directly into the trachea, has long been considered the gold standard for securing an airway. But it requires significant skill, direct visualization of the vocal cords, and practice to maintain proficiency. In chaotic prehospital environments with poor lighting, limited space, and patients who cannot be positioned ideally, intubation success rates drop. The King airway offered a compelling alternative: blind insertion that required far less training and could be performed by providers at every certification level.

In a simulated difficult-airway study, paramedics placed the King LT successfully 100% of the time with a mean placement time of 27 seconds. Compare that to a 69% success rate and 91 seconds for endotracheal intubation under the same conditions. Even basic EMTs, who do not normally perform intubation, achieved 100% success with the King airway in about 23 seconds.⁵ Most paramedics rated the King LT as “easy” or “very easy” to place, while many described endotracheal intubation as “difficult” in the same scenarios.

A large urban EMS system that switched its cardiac arrest protocol from paramedic-initiated endotracheal intubation to first-responder-initiated King LT-D placement found that basic life support providers inserted the King airway on the first attempt about 88% of the time, compared to a 58% first-attempt success rate for paramedic endotracheal intubation. Patients in the King group were roughly five times more likely to have a successful first attempt.⁶ That kind of difference in first-pass success is clinically meaningful: every failed airway attempt means time without adequate ventilation and additional trauma to the airway.

Not all studies showed the same advantage. One prehospital comparison found essentially identical overall placement success rates for King LTS-D and endotracheal intubation (about 80% for both), with no significant difference in time to placement either.⁷ The discrepancy likely reflects differences in provider experience, patient population, and how the studies measured success. In systems where paramedics intubate frequently and maintain proficiency, the gap narrows. Where intubation volumes are low and skills erode, the King airway’s simplicity becomes a bigger advantage.

Skill Retention Over Time

One of the strongest arguments for supraglottic devices like the King airway is that providers stay competent with them even without frequent practice. A study that tested paramedics on seven different airway devices found that endotracheal intubation success dropped from 78% during initial training to 58% three months later. The King LT-D, along with most other supraglottic devices tested, maintained a 100% success rate at the three-month mark. Time to ventilation was also significantly shorter for the King compared to intubation at every time point.⁸

This skill-retention gap has real implications. Many paramedics work in systems where they perform advanced airway management only a handful of times per year. A device that holds up without regular reinforcement is more reliable in those settings than one requiring ongoing practice to stay sharp.

The Shift in EMS Airway Practice

The adoption of supraglottic airways has reshaped how EMS systems manage airways during cardiac arrest. A longitudinal analysis of EMS data from 2011 to 2022 found that intubation attempts during cardiac arrest fell from about 87% of cases to 55%, while supraglottic airway attempts climbed from 25% to 61%.⁹ The King airway was a major driver of that shift, particularly in agencies that authorized basic-level providers to place it as a primary airway during cardiac arrest.

When one large urban EMS system implemented system-wide King LT use, the proportion of cases managed with endotracheal intubation dropped from about 72% to 67%. Importantly, the introduction of the King airway did not appear to erode intubation skill among the paramedics who still performed it; intubation success rates remained statistically unchanged.¹⁰ That finding addresses a concern some critics raised: that making a simpler device available would cause paramedics to lose their intubation skills through disuse.

Complications Worth Knowing About

The King airway’s inflatable cuffs exert pressure on surrounding tissue, which can cause problems when the device stays in place for an extended period. The most recognized complication is tongue engorgement. A case report described massive tongue swelling that developed roughly three hours after prehospital placement. The swelling was most likely caused by the oropharyngeal balloon compressing the veins that drain blood from the tongue, leading to progressive congestion.¹¹ This is not unique to the King airway, as other cuffed supraglottic devices can cause the same issue, but the King’s design with a large oropharyngeal balloon seems particularly prone to it. Emergency departments that receive patients with a King airway in place often prioritize swapping to a definitive airway promptly for this reason.

A more subtle concern involves blood flow to the brain. An animal study during simulated cardiac arrest measured carotid artery blood flow with various airway devices in place. Blood flow was significantly lower with the King airway, the LMA, and the Combitube compared to an endotracheal tube. Arteriograms confirmed that each supraglottic device compressed both the internal and external carotid vessels.¹² Whether this translates to worse neurological outcomes in humans remains debated, but it has contributed to growing interest in minimizing the time supraglottic airways remain inflated, particularly during prolonged resuscitation efforts.

Aspiration Protection and Its Limits

One selling point of the King airway is that by sealing the esophagus below the larynx, it should help prevent stomach contents from reaching the lungs. The gastric suction channel in the LTS-D variant adds another layer of protection. But the device does not seal as reliably as a cuffed tube sitting directly in the trachea. A cadaver study that tested six different airway devices during simulated CPR found aspiration in one out of five cases when the King LT was used, while no aspiration occurred with endotracheal intubation.¹³ The sample was small, but the finding is consistent with the broader principle that no supraglottic device offers the same level of aspiration protection as a properly placed endotracheal tube.

The King Airway Versus the i-Gel

For years, the King airway was the dominant supraglottic device in North American EMS. That position is now being challenged by the i-gel, a device with a gel-like non-inflatable cuff that conforms to the anatomy without requiring syringe inflation. Two large retrospective studies comparing the devices during out-of-hospital cardiac arrest have favored the i-gel on key outcomes.

One nationwide study found that i-gel use was associated with higher odds of first-pass airway success, return of spontaneous circulation, and survival to discharge compared to the King LT. Patients managed with the i-gel also had lower odds of experiencing rearrest.¹⁴ A separate analysis from the CARES surveillance group found that i-gel use was associated with about 45% higher odds of neurologically favorable survival compared to the King LT, along with better rates of hospital admission and discharge.¹⁵

These are observational studies, so unmeasured confounders could partly explain the gap. Agencies that adopted the i-gel earlier may differ in other ways from King-dominant systems. Still, the consistency across multiple large datasets has prompted many EMS agencies to reconsider their device choice. A study comparing five second-generation supraglottic airways placed by novice military operators found that the King LT variant had a lower first-attempt insertion rate than some competitors like the Supreme LMA and the i-gel, though it produced higher seal pressures.¹⁶ The i-gel has also proven superior for transitioning to a definitive airway: a cadaveric trial found significantly higher success rates for blind airway exchange through the i-gel compared to the King LT when using an intubating catheter.¹⁷

Pediatric Use

Pediatric airways are smaller, more anterior, and less forgiving of error, which makes any advanced airway procedure in children more stressful for providers. The King LT-D is available in pediatric sizes, and field data has been cautiously encouraging. A pilot study of prehospital pediatric King LT-D placement found a 95.5% success rate, with the median number of attempts being one and a mean placement time of 34 seconds.¹⁸ Providers who already had experience with the adult King airway felt their prior training prepared them well, and most strongly agreed they would use it as an alternative to pediatric intubation.

A simulation study comparing paramedic performance with the King LT and endotracheal intubation in a pediatric respiratory arrest scenario found similar insertion performance between the two, with most participants preferring the King.¹⁹ Pediatric emergency airways remain relatively rare events for most paramedics, so the lower skill threshold matters even more here than in adult practice.

Military and Tactical Settings

The King airway has found a role in tactical medicine, where the people managing airways may have far less medical training than civilian paramedics. A study tested whether combat lifesavers, who receive a much more abbreviated medical course than Special Operations Combat Medics, could successfully use the King LT-D. After brief instruction, 27 out of 28 students placed the device in under 60 seconds, with placement times comparable to those of the far more experienced medics. Self-rated confidence jumped dramatically, from about 1.4 out of 5 before training to 4.9 out of 5 afterward. Both groups recommended adding the device to the standard combat lifesaver kit.²⁰

The battlefield context amplifies many of the King airway’s advantages: minimal training required, no need for a laryngoscope or power source, rapid placement in low-visibility conditions. But it also amplifies the limitations. Prolonged evacuation times mean the device may stay in place for hours, raising the risk of tongue engorgement and vascular compression. Tactical medics need to monitor cuff pressures and assess for swelling during extended use, something that is easy to overlook when managing other injuries simultaneously.

Sore Throat and Patient Experience After Elective Use

While most of the discussion around the King airway focuses on emergency settings, the device has also been studied for use during routine surgery under general anesthesia. The postoperative experience gives a useful window into how the device affects the throat. In the controlled hospital study of 50 patients, about 22% reported a sore throat one hour after the procedure, and that dropped to 15% by 24 hours.²¹ One patient experienced laryngospasm and three had coughing episodes on removal. These numbers are broadly in line with what other supraglottic devices produce, though the King’s higher cuff pressures can contribute to more tissue irritation during prolonged procedures. The sore throat rates are generally lower than those seen after endotracheal intubation, where the tube passes between the vocal cords and direct mucosal contact is greater.