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Correspondence |
Vancouver General Hospital, Vancouver, Canada, E-mail: allidow{at}hotmail.com
To the Editor:
The two main challenges associated with endotracheal intubation using the Glidescope® videolaryngoscope have been identified as: 1) positioning the tip of the endotracheal tube (ETT) at the glottic opening, and 2) advancing the ETT off the stylet through the glottis into the trachea. In order to place the ETT at the laryngeal inlet Saturn Biomedical SystemsTM (Burnaby, BC, Canada, now renamed VerathonTM) recommend a 60° curvature to reproduce the curve of the Glidescope® blade.1 This approach is advocated by Cooper.2 Doyle et al. recommend a 90° "hockey stick configuration"3 and Dupanovic et al. describe a ‘gear stick’ technique.4 Other suggestions include Ushaped and J-shaped configurations – although these seem similar to the manufacturer’s recommendation. Others have recommended using midline insertion of the blade and ETT, and slightly withdrawing or relaxing the elevation of the laryngoscope tip while applying external laryngeal pressure. Various adjuncts have been suggested and used, including the Mallinkrodt Satinslip® intubating stylet (Tyco Healthcare Group LP, Pleasanton, CA, USA), the Parker Flex-it-Stylet (Parker Medical, Englewood, CO, USA), a modified Eschmann guide, or a gum elastic bougie.
A second difficulty is that once positioned at the glottic opening, it can be difficult to advance the ETT off the stylet and forward into the trachea. The 60° angulation of the Glidescope® and the excellent ‘upward’ view this affords, improves glottic exposure. However, by placing a 60° curve or a 90° ‘hockey stick’ configuration in the styleted ETT means that the ETT will always have a tendency to advance anteriorly off the stylet, and thus become lodged in the anterior commissure, or stuck on a cartilaginous ring on the anterior tracheal wall. Rotating the tube at this point can help to free the obstruction, but rotating a styleted ETT is not very easy. We have been using a technique that reduces the incidence of problems when advancing the ETT. Hung et al. have previously described this technique for both TrachlightTM and Glidescope intubation5 and we feel it warrants further discussion. We observe that most anesthesiologists use a 60° curvature, with the Satinslip® intubating stylet. Our method to overcome this obstruction is to load the ETT onto the stylet and lubricate in the same way, but to then bend the stylet in the direction opposite to the inherent memory of the ETT, i.e., the tube should be loaded and bent backwards against its natural curve. Thus, when the ETT is advanced off the stylet, or when the stylet is withdrawn, the ETT tip tends to angle more posteriorly, thus reducing the chance of impingement on the anterior glottis or anterior tracheal wall (Figure
).
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) was loaded normally along the curve of the inherent memory of the tube and bent to the exact curve of the glidescope blade. The tube in the lower panel (Figure) was loaded backwards against its inherent memory and bent in the same way. The stylets were both pulled back by 6 cm, to the proximal level of the cuff, to simulate stylet withdrawal and advancement of the ETT into the trachea. The difference in angle of advancement between the standard and reverseloaded ETT can clearly be seen. This procedure was performed ten times and the average difference in angle of advancement between the two techniques was 70°. This maneuver may help to reduce the incidence of difficulty when intubating the trachea using the Glidescope®. To show a clinical difference would require a randomized controlled trial.
Footnotes
Accepted for publication November 14, 2006.
References
1 Glidescope® Videolaryngoscope, Operator and Service Manual. Saturn Biomedical Systems Inc. (Now VerathonTM), Burnaby, BC, Canada. Available from URL; www.verathon.ca.
2 Cooper RM. Videolaryngoscopy in the management of the difficult airway (Letter, reply). Can J Anesth 2004; 51: 95–6.
3 Doyle DJ, Zura A, Ramachandran M. Videolaryngoscopy in the management of the difficult airway (Letter). Can J Anesth 2004; 51: 95.
4 Dupanovic M, Diachun CA, Isaacson SA, Layer D. Intubation with the GlideScope® videolaryngoscope using the ‘gear stick technique’ (Letter). Can J Anesth 2006; 53: 213–4.
5 Hung OR, Tibbet JS, Cheng R, Law JA. Proper preparation of the TrachlightTM and endotracheal tube to facilitate intubation (Letter). Can J Anesth 2006; 53: 107–8.
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  A. Lane and G. Lewis Combined use of a videolaryngoscope and a transilluminating device for intubation Can J Anesth, July 1, 2007; 54(7): 589 - 590. [Full Text] [PDF]
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