To the Editor:--We read with interest the description by Hornbein et al. of a laryngeal mask airway (LMA) connected to the anesthetic circuit by two right-angle elbows with membrane-covered access ports. This is a useful approach to instrumentation of the larynx and trachea but the technique is limited by the increased resistance to gas flow secondary to the presence of a stylet and a fiberoptic scope in the LMA tube. This may be particularly problematic in pediatric patients when the ratio of instrument size to tube internal diameter is high. We would like to describe a prototype LMA undergoing evaluation that offers similar advantages but overcomes the problems of gas flow.
The prototype, the double-lumen LMA (DL-LMA), comprises a standard LMA with an additional tube fused onto the posterolateral aspect of the main tube just proximal to the cuff (Figure 1). The anesthesiologist adds membrane-covered access ports to each tube as suggested by Hornbein et al. Insertion of the DL-LMA is similar to the standard device, and when using it for diagnostic laryngobronchoscopy, the fiberoptic scope is passed down the main tube, and the additional tube is connected to the circuit. When using it as an airway intubator, the fiberoptic scope and circuit are connected to the additional tube, and the airway instruments are passed via the main tube.
Gas flows for the #2.5 DL-LMA were compared with the standard #2.5 LMA using a Puritan Bennet 7200a ventilator (Carlsbad, CA) set at a tidal volume of 250 ml, respiratory rate of 15 breaths/min, and the waveform set to square flow (common ventilatory settings for a 20-kg child). Peak inspiratory flows were 15, 30, 45, and 60 l *symbol* min sup -1 and the peak pressures recorded with and without a fiberoptic scope (outer diameter 4 mm). Peak airway pressures were 26-43% less with the #2.5 DL-LMA compared with the #2.5 LMA in the presence of a fiberoptic scope (Figure 2). Peak airway pressures were similar without the fiberoptic scope.
A dedicated intubating LMA with a short, wide-bore tube and guiding handle, undergoing clinical trails, provides a further possible solution to the problems of size limitation and gas flow. Neither the DL-LMA nor the intubating LMA are available in the United States.
M. Lopez-Gil, M.D., Consultant Anaesthesiologist, Department of Anaesthesia and Reanimation, Maranon University Hospital, Madrid, Spain.
J. Brimacombe, F.R.C.A., Clinical Associate Professor, University of Queensland Cairns Base Hospital, Cairns, Australia.
A. I. J. Brain, F.F.A.R.C.S.I., Honorary Consultant Anaesthetist, Royal Berkshire Hospital, Reading, United Kingdom.
D. J. Wenck, F.F.I.C.A.N.Z.C.A., Consultant Intensivist, Cairns Base Hospital, Cairns, Australia.
H. A. Wilkins, E.N., Ventilator Technician, Cairns Base Hospital, Cairns, Australia.