Variations in ILMA external diameters: another cause of device failure

Purpose: To report failure of insertion of #5 and #4 intubating laryngeal m ask airways (ILMAs) in a patient with a mouth opening of just under 25 mm, and the variances among same-size ILMAs. Clinical features: A 53-yr-old man with obstructive sleep apnea underwent e lective ENT surgical repair. His mouth opening was just under 25 mm. Ventil ation by mask was easy. Direct laryngoscopy failed after induction of anest hesia and neuromuscular block. Neither a #5 nor a #4 ILMA could be passed b etween the patient's teeth, despite different twisting maneuvres. A #4 LMA was thus prepared as a conduit for fibreoptic intubation. Placement of the IMA was easy, as was fibreoptic-guided intubation. The LMA was removed over the tracheal tube (TT) to enable ENT surgery, and the further course was u neventful. Manual examination showed that, unlike others of the same type, the failed ILMAs were not sufficiently compressible either to allow inserti on in this patient or to the 20 mm reported as the maximal outer dimension of the device. Radiological examination revealed that, at the point of the device where it is intended to be compressible, the silicone layer was thic ker in the failed devices than in stock compressible ILMAs, and the end of the steel tube was not so sharply beveled. Conclusion: Our inability to insert an ILMA in a patient with an interdenta l distance of just under 25 mm was because the device was not sufficiently compressible although the manufacturer states the maximal outer dimension t o be 20 mm.