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01.12.2014 | Research article | Ausgabe 1/2014 Open Access

BMC Anesthesiology 1/2014

Extubation force depends upon angle of force application and fixation technique: a study of 7 methods

BMC Anesthesiology > Ausgabe 1/2014
Jennifer L Wagner, Robin Shandas, Craig J Lanning
Wichtige Hinweise

Electronic supplementary material

The online version of this article (doi:10.​1186/​1471-2253-14-74) contains supplementary material, which is available to authorized users.

Competing interests

Funding for materials (endotracheal tubes, restraint devices, test fixation device construction) and personnel time (design and fabrication of test and required equipment, data collection) were provided, in part, by Securisyn Medical, LLC. Time for data analysis and manuscript generation was paid for solely by the University of Colorado, Denver Department of Bioengineering. All data collection, analysis and manuscript generation were performed solely by the authors of this manuscript.

Authors’ contributions

RS secured funding and provided guidance and management throughout all phases of this study. CL provided equipment and software training. JW, RS and CL participated in study conception, design, execution, analysis and manuscript organization. JW designed the test fixture and performed all data collection. JW, CL and RS participated in data analysis. Manuscript was prepared by JW. JW, RS and CL all read and approved this manuscript for submission.



Endotracheal tubes are frequently used to establish alternate airways. Precise placement of the tubes must be maintained to prevent serious complications. Several methods for fixation of endotracheal tubes are available. Available methods vary widely in form and functionality. Due to the unpredictable and dynamic nature of circumstances surrounding intubation, thorough evaluation of tube restraints may help reduce airway accidents such as tube dislodgement and unplanned extubation.


Seven different tube-restraint combinations were compared against themselves and one another at a series of discrete angles (test points) covering a hemisphere on the plane of the face. Force values for tube motion of 2 cm and 5 cm (or failure) were recorded for 3 pull tests, at each angle, for each method of tube fixation.


All methods showed variation in the force required for tube motion with angle of force application. When forces were averaged over all test points, for each fixation technique, differences as large as 132 N (30 lbf) were observed (95% CI 113 N to 152 N). Compared to traditional methods of fixation, only 1 of the 3 commercially available devices consistently required a higher average force to displace the tube 2 cm and 5 cm. When ranges of force values for 5 cm displacement were compared, devices span from 80–290 N (18–65 lbf) while traditional methods span from 62–178 N (14–40 lbf), highlighting the value of examining forces at the different angles of application. Significant differences in standard deviations were also observed between the 7 techniques indicating that some methods may be more reproducible than others.


Clinically, forces can be applied to endotracheal tubes from various directions. Efficacies of different fixation techniques are sensitive to the angle of force application. Standard deviations, which could be used as a measure of fixator reliability, also vary with angle of force application and method of tube restraint. Findings presented in this study may be used to advance clinical implementation of current methods as well as fixator device design in an effort to reduce the incidence of unplanned extubation.
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