Comparison of the Air-Q® Self-Pressurizing (SP) Intubating Laryngeal Airway With the Air-Q® Intubating Laryngeal Airway and I-gel for Airway Maintenance in Adults Under General Anesthesia

Laryngeal mask airways (LMAs) are a group of airway devices, alternatively referred to as supraglottic airways (SGAs), used in anesthesia that are positioned in the back of the throat (pharynx) above (supra) the glottis (windpipe opening) and the vocal cords. This is in contradistinction to a tracheal tube, which is an airway device that is placed through the vocal cords and extends to a position below the glottis (infraglottic) and resides in the trachea (windpipe). Since their first approval for use in the United States by the US Food and Drug Administration in the early 1990s, the application of SGAs has become more widespread. Initially, they were only used in anesthetized patients who were breathing on their own (i.e., spontaneously ventilating). This was, in large part, due to a relatively low airway seal pressure, the pressure with which the device seals against the throat, thereby, keeping the air pushed in by a breathing machine (ventilator) from getting into the stomach or leaking out around the device and out through the mouth - in either case, not going into the patient's lungs. The relatively low airway seal pressure (18 - 20 cmH2O) did not allow for the use of muscle relaxant (paralyzing) drugs and positive pressure ventilation. Successive generations of SGAs by a variety of manufacturers have overcome and continue to attempt to overcome limitations of earlier devices. In addition, accumulated clinical experience has made anesthesia providers more comfortable with their use. No SGA, however, is yet ideal, and incremental changes continue to appear to improve airway management and reduce airway morbidity (e.g., sore throat, jaw pain, etc.).

The air-Q® Intubating Laryngeal Airway (aILA, Mercury Medical, Clearwater, FL) is a newer, commercially-available, SGA designed for use as a primary airway and as an intubation conduit. It is available in polyvinyl chloride (PVC)-based, single use and silicone-based, reusable models. Information on its safety and effectiveness from a randomized, controlled trial in adults, undergoing general anesthesia, compared to that of the silicone-based, reusable aILA versus the LMA-Proseal™ (pLMA, North America, San Diego, CA), the current "gold standard" for SGA airway seal pressure, is available.

The air-Q® Self-Pressurizing (SP) Intubating Laryngeal Airway (aILA-SP, Mercury Medical, Clearwater, FL) is a commercially-available, modification of the silicone-based, reusable aILA. Its overall design is identical to the aILA, but incorporates a communication orifice between the air tube and cuff, which regulates airflow into and from the cuff during periods of positive pressure and spontaneous ventilation. As such, it incorporates a self-pressurizing cuff that does not require manual inflation. Such a cuff may be advantageous insofar as it dynamically adjusts its intra-cuff pressure and fit with the patient's pharyngeal and periglottic anatomy, which may lead to a reduction in airway morbidity, while still providing the high seal pressure afforded by the aILA design.

Lastly, the i-gel (Intersurgical Inc., Liverpool, NY) is a commercially-available SGA that uses a thermoplastic elastomer to create a non-inflating, anatomically-conforming, periglottic cuff. Studies have shown it to be an easily inserted, effective airway device with a lower incidence of sore throat and neck complaints. With exception to the aILA-SP, it is the only other commercially-available SGA that does not require cuff inflation.

To date, no reports are available on the clinical performance of the aILA-SP in relation to other SGAs. Thus, the primary purpose of this study is to compare the airway seal pressure (ASP) of the aILA-SP against the aILA and i-gel in adults undergoing general anesthesia. Airway seal pressure is the most common surrogate for ventilatory capacity used in SGA studies.