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Anesth Analg 1999;88:1422
© 1999 International Anesthesia Research Society


LETTERS TO THE EDITOR

Glottis Simulator

Roberto de Menezes Lyra, MSc

IAMSPE Serviço de Cirurgia Torácica 04049-901 S|Atao Paulo, Brazil

The complexity of endotracheal intubation is often mentioned in the literature (13). Moreover, the Carlens double-lumen tube (4) is troublesome to passes beyond the glottis during intubation because of carinal hook. At this stage, the tube is rotated so as not to damage the vocal cords. Although superior polyvinyl chloride tubes are available, the "hooked tubes" are still used.

After the patient is anesthetized and paralyzed, the double-lumen tube is inserted into the trachea using a rigid laryngoscope. The tube is held such that the tip of the bronchial lumen faces anteriorly... With the Carlens—left sided—or White—right sided—tubes, as the tip of the bronchial lumen passes the vocal cords, the tube is rotated 180° to bring the carinal hook passes anteriorly to negotiate the vocal cords. After the carinal hook passes beyond the vocal cords, the Carlens tube is rotated 90° to the right, whereas the White tube is rotated 90° to the left, in order to have the bronchial lumen face the intended bronchus. Once the double-lumen tube is placed in the trachea, the tracheal cuff is inflated. Mechanical ventilation is then begun with tidal volume of 10 ml/kg and a rate of 8 breaths/min. The bronchofiberscope is then used to evaluate the bronchial tree and the position of the double-lumen tube (5).

Unfortunately, there is no simulator to teach such maneuvers by using three-dimensional visualization. To decrease such difficulties, a glottis simulator was developed to help in the training of tube rotation maneuvers.

A disposable plastic coffee cup (50 mL) was used to make the simulator. At the base of plastic cup, on the external side, three cuts and two indentures were made with the sharp point of a disposable 30 x 1.5-mm needle. Two of the cuts are straight and symmetrical: x - x', x'' - x'''; the other cut is semicircular y - y', as shown in Figure 1A.



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Figure 1. Schematic design of the different phases of the construction of the glottis simulator. A, View of the base of the plastic cup with cuts x - x', x'' - x''' and y - y'. B, View of the bottom of the plastic cup with the indentures (scored lines) z - z' and z'' - z'''. C, Lateral view of the plastic cup. The arrow indicates the folding maneuver of the "epiglottis." D, Lateral view of the plastic cup with the final positioning of the "epiglottis." E, Upper view of the plastic cup with the maneuvers to make the "vocal cords" malleable. F, Upper view of the plastic cup with the final form of the glottis simulator. e = "epiglottis" and vc = vocal cord.

 
The two straight indentures (scored lines), z - z' and z'' - z''', are also symmetrical, as indicated in Figure 1B.

Figure 1 C–E shows the folding maneuvers to simulate the anatomical structures, as follows. Figure 1C shows the "epiglottis," located in the central part of the bottom of the cup and delimited by the three cuts x - x', x'' - x''' and y - y'. The "epiglottis" must be pressed and inverted toward the interior of the plastic cup, folding in to the level of its vertex, as indicated by the curved arrow. Figure 1D illustrates how the "epiglottis" must be positioned. The lateral delimitation of the two "vocal cords" are established by the respective indentures (scored lines) z - z' and z'' - z'''. These must be folded at the level of the indentures, flexed several times to become pliable, and bent toward the outside of the cup, as demonstrated in Figure 1E. The plastic cup must be internally greased with lidocaine spray to facilitate the sliding over its surface.

References

  1. Fridrich P, Frass M, Krenn CG, et al. The Upsherscope in routine and difficult airway management: a randomized, controlled clinical trial. Anesth Analg 1997;85:1377–81.[Abstract]
  2. Mallampati SR, Gatt SP, Gugino LD, et al. A clinical sign to predict difficult tracheal intubation: a prospective study. Can J Anaesth 1985;32:429–34.[Abstract/Free Full Text]
  3. Adnet F, Borron SW, Racine SX, et al. The Intubation Difficulty Scale (IDS): proposal and evaluation of a new score characterizing the complexity of endotracheal intubation. Anesthesiology 1997;87:1290–7.[ISI][Medline]
  4. Carlens E. A new flexible double-lumen catheter for bronchospirometry. Thorac Surg 1949;18:742–6.
  5. Ovassapian A. Conduct of anesthesia. In: Shields TW, ed. General thoracic surgery. 4th ed.Baltimore:Williams & Wilkins, 1994:307–23.




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Lippincott, Williams & Wilkins Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999 HighWire Press