Distance from the glottis to the grille: the LMA Unique, Air-Q and CobraPLA as intubation conduits: a randomised trial.

BACKGROUND: Supraglottic airway devices are often used in airway management to facilitate tracheal intubation. Knowledge of the distance from the grille of the device to the patient's vocal cords is essential for the safe passage of the tracheal tube below the vocal cords.

OBJECTIVES: To assess the distance from the glottis to the grille of three supraglottic airway devices [LMA (LMA Unique), Air-Q (Air-Q Intubating Laryngeal Airway Reusable) and CobraPLA (Cobra Perilaryngeal Airway)] and their safe usage as intubation conduits.

DESIGN: Randomised controlled trial.

SETTING: Tertiary, university hospital.

PATIENTS: Thirty women undergoing elective gynaecological surgery with planned supraglottic airway management.

INTERVENTIONS: In-vivo fibreoptic assessment and in-vitro measurement.

MAIN OUTCOME MEASURES: The distance from the grille to the glottis was defined as primary outcome. The distance from the beginning of the cuff of a tracheal tube passed through the device to the grille was assessed as secondary outcome.

RESULTS: The three devices exhibited significant differences in the mean ± SD distance from the glottis to the grille (LMA 4.6 ± 1.5  cm, Air-Q 5.7 ± 1.4  cm, CobraPLA 3.4 ± 1.4  cm; P = 0.009). The Air-Q was predicted to allow the safe passage of a tracheal tube into the trachea, whereas the cuff was predicted to rest on the vocal cords in 57% of the LMA patients and 14% of the CobraPLA patients.

CONCLUSION: Using the LMA Unique as a conduit for tracheal intubation may pose a safety risk, whereas the use of the Air-Q would position the tracheal tube at a safe depth in the trachea.