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October 19, 2008
9:00 AM - 11:00 AM
Room Hall E2-Area G,
Influence of the Tube Diameter on the Endotracheal Tube Advancement with the Airtraq Laryngoscope
Akiko Yoshida, M.D., Misa Komai, M.D., Takahiro Sugiura, M.D., Takehiko Kaneko, M.D., Yoshiro Kobayashi, M.D., Ph.D.
Anesthesiology, National Tokyo Medical Center, Meguro, Tokyo, Japan

The Airtraq laryngoscope (ATQ: Prodol Ltd., Vizcaya Spain) is a novel intubation device that will possess advantages to provide a high-quality view of the glottis. However, it remains difficult for less experienced anesthesiologists to place the endotracheal tube (ETT) in the trachea even though using ATQ. The main difficulty will result from unexpected downward advancement of the ETT. In our experience, such cases were commonly encountered in using the smaller ETT. We, therefore, hypothesized that the ETT diameter would affect the direction of the ETT advancement.


Our experimental setup consisted of a regular size ATQ with a built-in video system, small target boards and two sizes of ETT (Safety clear, RUSCH): ID of 7.0 mm (ETT-7.0), 7.5 mm (ETT-7.5). Additionally, a marker pen was placed at the center of each ETT tip for the purpose of leaving the impact point of the advancing ETT tip on a target.


In advance of every trial, a blank target board was fixed perpendicularly to the optical axis of ATQ and placed at 1cm ahead of its blade tip, where the glottis was approximately located in clinical practice of ATQ. Subsequently, six trials for each ETT were randomly performed: the ETT, with its cuff deflated and lubricated, was advanced slowly trough the tube guiding channel of ATQ. After reaching a target board, the ETT was withdrawn. In all trials, video-clips recorded from the built-in camera of ATQ were stored on a PC for later analysis. Both vertical and horizontal gaps between the center of the visual field of ATQ and the trace of the ETT tip were measured using the image analysis software Image Pro-Plus (Version 5.1, Media Cybernetics, Silver Spring, MD). Statistical analysis between two groups was performed with the independent t-test using SPSS ver.12. Data are presented as mean +/-SD. P-value < 0.05 was considered significant.


The downward gap in ETT-7.5 trials was significantly smaller (0.17 +/- 0.21 mm; P < 0.0001) than those in ETT-7.0 trials (3.98 +/- 0.84). As for the horizontal displacement, the left-side gap in ETT-7.0 trials was significantly smaller (2.38 +/- 0.41; P < 0.0001) than those in ETT-7.5 trials (6.37 +/- 0.30).


Most anesthesiologists have tended to believe that the ETT will advance towards the center of the visual field of ATQ. However, our results showed that the ETT would advance downward and/or left side of the visual field at least in the limited settings. These discrepancies will be reasonably associated with the physical properties of the ETT. Specifically, both the mount alignment and the advancement direction of the ETT were determined by two physical factors. The main factor was the gap between the outer diameter of the ETT and the inner size of the tube guiding channel of ATQ. The secondary was the material characteristics of the ETT, e.g., stiffness, shape, etc.


Given the lack of detailed data with a variety of ETTs, the direction of the ETT advancement will be associated with the physical properties of it, in particular its diameter. The knowledge of these relationships is very informative for beginners and will successfully ensure a rapid intubation with ATQ. Further studies investigating various ETTs in clinical settings are required to predict the advancement direction of the ETT during ATQ procedure.

Anesthesiology 2008; 109 A525