To the Editor:
Fiberoptic tracheal intubation under general anesthesia may be performed either with the patient breathing spontaneously or after intravenous induction of anesthesia and neuromuscular blockade . In a previous study  we have demonstrated that a size 3 laryngeal mask airway (LMA) can be split along its longitudinal axis and the cuff resealed with room temperature vulcanizing silicone to allow autoclaving. Although oxygenation in this previous study  was maintained in all patients, the adequacy of carbon dioxide elimination was not assessed. Twenty patients aged 18 yr or over requiring orotracheal intubation were studied. They were randomly allocated into two groups: 1) split laryngeal mask or 2) Berman airway. Anesthesia was maintained by the spontaneous respiration of isoflurane (alveolar concentration 1%-2%) in nitrous oxide and oxygen (FIO2 = 0.4). The fiberscope (Olympus LM-1) was inserted through the split laryngeal mask or Berman airway. When a good view of the vocal cords was obtained, the "scope" was inserted and passed into the trachea. The airway device was removed and intubation of the trachea completed. There was a statistically significant difference between the groups when PaCO2 was compared at two measurement intervals after insertion of the anesthetic delivery system (P < 0.025). Using a split LMA we have confirmed that the patient's airway is secure, and pulmonary ventilation is more effective when the split LMA technique is used as a training aid for fiberoptic tracheal intubation.
James M. Murray, MD, FFARCS
Craig W. Renfrew, FRCA
Department of Anaesthesia, The Ulster Hospital, Belfast BT 16 ORH, United Kingdom
1. Smith JE, MacKenzie AA, Scott-Knight VCE. Comparison of two methods of fibrescope guided tracheal intubation. Br J Anaesth 1991;66:546-50.
2. Darling JR, Keohane M, Murray JM. A split laryngeal mask as an aid to training in fibreoptic tracheal intubation. Anaesthesia 1993;46:1079-82.