Air-Q Intubating Laryngeal Airway Versus the Laryngeal Mask Airway (LMA)-Proseal

Introduction:

The air-QⓇ Intubating Laryngeal Airway (ILA) (Mercury Medical, Clearwater, Fl.) is a newer supraglottic airway. It is approved for use as a primary airway and as an aid for intubation in situations of anticipated or unanticipated difficult airways. A unique feature of this device as compared to other airways on the market is the size of the inner diameter (ID) and length of its airway tube. Direct placement of tracheal tubes > 7.5 mm ID through the airway tube is possible.

The ProSealTM LMA (LMA North America, La Jolla, CA) is considered the gold standard for supraglottic devices with respect to airway seal pressure. On average, it is reported to be approximately 28 cmH2O. This is significantly higher than that of the first generation LMA, the LMA-ClassicTM, which has a maximum seal pressure of 20 cmH2O, but averages 16-18 cmH2O in actual practice.

Pilot data from 50 insertions of the air-QⓇ at our institution places the device intermediate to the two aforementioned LMAs with regard to seal pressure, with a mean seal pressure of 23 (12-30) cmH2O.

Specific Aims:

1. To test whether the air-QⓇ creates an airway seal pressure that is similar to the LMA-ProSealTM.
2. To test whether the position of the air-QⓇ in relation to the vocal cords, as assessed by fiberoptic endoscopy, is similar to that of the LMA-ProSealTM.
3. To test whether airway morbidity is similar between the air-QⓇ and the LMA-ProSealTM

Study design:

Prospective, single-center, randomized, controlled trial

Methods:

The patient will be met in the pre-operative area by the attending anesthesiologist, who interviews and examines the patient. A full explanation of the general anesthetic, including risks and benefits, will be given and informed consent obtained. An intravenous catheter will be placed and patients will be premedicated as needed at the discretion of the attending anesthesiologist. In the operating room, the patient will undergo standard monitoring per established American Society of Anesthesiology (ASA) guidelines. After a period of breathing 100% oxygen by facemask, anesthesia will be induced intravenously typically with fentanyl 0.5-1.5 mcg.kg -1 (a fast acting narcotic) and propofol (a potent sedative/amnestic agent) 2-3 mg.kg -1. After eyelash reflex is lost (i.e. the patient is asleep and not breathing), the patient will typically be ventilated with a facemask to demonstrate the patency of the airway. The LMA will then be placed using a standard technique. The cuff of the LMA will be inflated and the adequacy of placement assessed by presence of end-tidal carbon dioxide and adequate chest rise. The airway seal pressure will then be assessed by closing the APL valve on the anesthesia machine with a fresh gas flow of 5 liters/minute until an audible leak is observed. A stethoscope will be placed over the stomach while the valve is closed to listen for gastric insufflation. Administration of other anesthetic medication or muscle relaxants is at the discretion of the anesthesiologist and based on their clinical judgment and/or at the request of the surgeon. The anesthesia provider will not be blinded and will have access to all the monitors. The study deviates from routine care in that the choice of which LMA to use will be randomized by opening a sealed envelope prior to the start of the case. In addition, once the LMA has been placed and secured and the patient is stable from an anesthetic point of view, a flexible fiberoptic camera will be place into the airway tube of the LMA and the view of the patient's vocal cords in relation to the cuff of the LMA will be assessed.

At the conclusion of the case, when the patient is breathing on their own and is awake enough, as judged by the anesthesia provider, the LMA will be removed, as would be otherwise done as standard of care. The study LMA will be examined by a data collector for the presence of grossly visible blood or bile, and its presence or absence will be recorded. In the recovery area, once the patient is fully awake, as judged by the recovery staff, an observer will administer a standard oral questionnaire to the patient to determine if a sore throat, difficulty swallowing, or difficulty speaking is present. The patient will be called 24 hours later by the data collector and the same questionnaire will be administered.