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Changes in resistances of endotracheal tubes with reductions in the cross-sectional area

Published online by Cambridge University Press:  01 April 2008

M. F. El-Khatib ,
A. Husari ,
G. W. Jamaleddine ,
C. M. Ayoub  and
P. Bou-Khalil
M. F. El-Khatib*
Affiliation:
American University of Beirut, Departments of Anesthesiology, Beirut, Lebanon
A. Husari
Affiliation:
American University of Beirut, Departments of Internal Medicine, Beirut, Lebanon
G. W. Jamaleddine
Affiliation:
American University of Beirut, Departments of Internal Medicine, Beirut, Lebanon
C. M. Ayoub
Affiliation:
American University of Beirut, Departments of Anesthesiology, Beirut, Lebanon
P. Bou-Khalil
Affiliation:
American University of Beirut, Departments of Internal Medicine, Beirut, Lebanon
*
Pierre Bou-Khalil, Department of Internal Medicine, American University of Beirut, P.O. Box: 11-0236, Beirut1107 2020, Lebanon. E-mail: pb05@aub.edu.lb; Tel: +96 13224609; Fax: +96 11370814
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Summary

Background and objectives

Partial obstruction of endotracheal tubes due to accumulation of secretions and mucus plugs can increase the tube resistance and subsequently impose increased resistive load on the patient. This study was performed to determine the changes in the resistance of endotracheal tubes of sizes 7.5, 8.0 and 8.5 mm with different degrees and locations of endotracheal tube narrowing.

Methods

Reductions of 10%, 25%, 50% and 75% in the endotracheal tube’s cross-sectional areas were created at different sites along the axes of the tube connected to an artificial lung. While ventilating with a constant inspiratory flow, a 1 s end-inspiratory occlusion manoeuvre was applied and the resulting plateau pressure was determined. The resistance was calculated as (peak airway pressure – plateau pressure)/peak inspiratory flow.

Results

Significant increases in the endotracheal tube’s resistances were observed as the tube’s cross-sectional area reduction was increased from 25% to 50% and from 50% to 75% for the 7.5 mm endotracheal tube, from 25% to 50% for the 8.0 mm endotracheal tube, and from 50% to 75% for the 8.5 mm endotracheal tube. Changes of the endotracheal tube resistances were not affected by the site of cross-sectional area reductions along the axes of the tubes.

Conclusions

For endotracheal tubes of sizes 7.5, 8.0 and 8.5 mm, significant changes in the tubes resistances are observed when the partial obstructions of the tubes exceed certain critical values. The location of the partial obstruction did not affect the changes in the endotracheal tube resistances.

Keywords

AIRWAY RESISTANCE, endotracheal tubesWORK OF BREATHINGINTUBATION INTRATRACHEAL
Type
Original Article
Information
European Journal of Anaesthesiology , Volume 25 , Issue 4 , April 2008 , pp. 275 - 279
Copyright
Copyright © European Society of Anaesthesiology 2008

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