Airway Adjuncts and Supraglottic Airway Devices

Airway management has been the cornerstone of emergency medicine since practitioners first recognized that respiratory failure is among the most rapidly fatal conditions a patient can experience. Before the development of modern airway devices, clinicians relied almost exclusively on manual maneuvers such as the head-tilt/chin-lift and jaw thrust, along with crude improvised tools, to maintain an open passage for air to reach the lungs. The mortality rates associated with airway obstruction in unconscious patients were staggeringly high, particularly in the prehospital setting where definitive surgical airways or endotracheal intubation were impractical. This gap between basic manual techniques and advanced surgical interventions created a pressing clinical need for intermediate devices—tools that could be placed quickly by trained providers to secure the airway without requiring direct visualization of the vocal cords. The development of airway adjuncts and supraglottic airway devices (SGAs) represents one of the most significant advances in prehospital airway management over the past century.

The central question that drove the evolution of these devices remains the same one AEMT providers face on every call: how can a rescuer rapidly secure a compromised airway in a patient who cannot protect it, particularly when endotracheal intubation is not within the provider's scope or when conditions make it impractical? Understanding the history and rationale behind airway adjuncts and SGAs equips you to select the right device for each clinical scenario with confidence.

Before examining individual devices in detail, it is essential to establish the foundational principles that govern airway adjunct selection and use. Every device discussed in this lesson operates on the same fundamental premise: the upper airway of an unconscious or semiconscious patient is prone to obstruction—most commonly by the tongue falling posteriorly against the pharyngeal wall—and a mechanical device can physically prevent that obstruction or bypass it altogether. The distinction between basic airway adjuncts (OPA and NPA) and supraglottic airway devices lies in their placement relative to the glottis and the degree of airway protection they offer.

The diagram above illustrates the critical anatomical relationships that govern adjunct placement. On the left, you can see how the tongue occupies a substantial volume of the oropharynx; in an unconscious patient, loss of muscle tone allows it to fall posteriorly and occlude the airway at the level of the hypopharynx. The OPA follows the natural curvature of the palate, with its distal tip resting in the posterior oropharynx to physically displace the tongue forward. The NPA takes a different route entirely, passing through the nostril along the floor of the nasal cavity and into the nasopharynx, bypassing the oral cavity altogether. Note the sizing landmarks: an improperly sized device not only fails to serve its purpose but can actively harm the patient through trauma or further obstruction.

Supraglottic airway devices occupy an intermediate position on the airway management hierarchy, sitting above the level of the glottis (hence the name "supraglottic") to create a functional seal that permits positive-pressure ventilation without entering the trachea. Unlike an endotracheal tube, which passes through the vocal cords and directly seals the trachea, an SGA forms its seal in the hypopharynx surrounding the laryngeal inlet. This distinction is fundamental to understanding both the advantages and limitations of these devices in the prehospital setting.

Seal Mechanisms

SGAs achieve their airway seal through one of two primary mechanisms. Inflatable-cuff devices (such as the King LT and classic LMA) use an air-filled cuff that, once inflated, conforms to the tissues of the hypopharynx and creates a low-pressure seal around the glottic opening. The King LT (Laryngeal Tube) employs a dual-cuff design: a larger proximal cuff that occludes the oropharynx and a smaller distal cuff that seats in the upper esophagus, with ventilation ports positioned between the two cuffs directly over the glottic opening. Non-inflatable devices (such as the i-gel) use a pre-formed thermoplastic elastomer cuff that conforms to the perilaryngeal anatomy through body-heat softening, eliminating the need for cuff inflation and reducing insertion time.

Ventilation Through an SGA

Once seated, the SGA's lumen provides a direct channel from the 15-mm standard connector (which attaches to a bag-valve-mask or ventilator circuit) through the device to the ventilation aperture at the distal end. When positive pressure is applied, air flows through this channel and enters the trachea through the glottic opening. The seal around the glottis prevents air from escaping into the esophagus or back through the oropharynx, though the quality of this seal is quantified by the oropharyngeal leak pressure (OLP). Most modern SGAs achieve an OLP of 20–30 cmH₂O, which is sufficient for most clinical ventilation needs but substantially lower than the seal provided by a properly placed endotracheal tube.

Second-Generation SGAs and Gastric Access

A major advancement in SGA design is the incorporation of a gastric drainage channel. Second-generation SGAs such as the LMA Supreme, i-gel, and King LTS-D include a separate port that aligns with the esophageal opening, allowing passage of a gastric tube to decompress the stomach. This is clinically significant because gastric distension from bag-valve-mask ventilation increases the risk of regurgitation and aspiration. By providing a channel for passive or active gastric drainage, second-generation devices substantially mitigate one of the chief hazards of supraglottic ventilation.

AEMT providers must be familiar with a range of airway devices, understanding when each is indicated, contraindicated, and how they relate to one another on the airway management continuum. The following classification organizes devices by their anatomical positioning and functional capability, followed by a detailed comparison table that serves as a rapid clinical reference.

Device selection in the field is governed by patient presentation, available equipment, and local protocols. In general, the AEMT should first attempt basic manual maneuvers combined with suctioning, escalate to an OPA or NPA as appropriate, and if ventilation remains inadequate or the patient requires ongoing positive-pressure ventilation, advance to an SGA. The specific SGA chosen will depend on what is stocked on the unit and what the provider has been trained and authorized to use. Many EMS systems have standardized on a single SGA platform—often the King LTS-D or i-gel—to simplify training and reduce decision fatigue under stress.

Consider the following clinical scenario: You are dispatched to a 58-year-old male found unresponsive in his home by family members. He is supine on the floor, breathing with sonorous (snoring) respirations at a rate of 6 breaths per minute. He is unresponsive to painful stimuli. No gag reflex is present. Your partner is performing bag-valve-mask ventilation but is reporting significant difficulty achieving adequate chest rise despite a jaw thrust and proper mask seal. Your service carries King LTS-D devices. Walk through the clinical decision-making and insertion process step by step.

No single airway device is perfect for every clinical scenario. Understanding the relative strengths and limitations of each option allows the AEMT to make informed, rapid decisions. The table below provides a side-by-side comparison of the three most commonly encountered SGAs in prehospital practice, evaluated across the parameters most relevant to field use.

While SGAs represent a significant advancement over basic adjuncts, they remain a bridge to more definitive airway management in many clinical scenarios. Understanding how SGAs fit within the broader airway management continuum prepares the AEMT to collaborate effectively with paramedic and physician partners, and also establishes a conceptual foundation for providers who advance to the paramedic level. The table below contrasts SGAs with endotracheal intubation (ETI), the traditional gold standard for definitive airway management in the prehospital setting.

Recent literature, including landmark studies such as the AIRWAYS-2 and PART trials, has challenged the assumption that ETI always produces superior outcomes compared to SGAs in prehospital cardiac arrest. In several large randomized controlled trials, SGAs demonstrated non-inferior or even superior neurological outcomes compared to ETI when performed by paramedics in the field. These findings have led many EMS systems to adopt SGAs as the primary advanced airway in cardiac arrest, reserving ETI for specific indications or post-return-of-spontaneous-circulation (ROSC) scenarios. For the AEMT, the practical implication is clear: mastery of SGA placement is not merely a stepping stone to intubation—it is a clinically valuable skill in its own right that may be the most important airway intervention you perform in cardiac arrest management.