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         Journal List > Korean J Intern Med > v.26(4); Dec 2011
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Korean J Intern Med. 2011 Dec;26(4):421-426.
Published online 2011 November 28.  http://dx.doi.org/10.3904/kjim.2011.26.4.421
Copyright © 2011 The Korean Association of Internal Medicine
Sound Analysis in an In Vitro Endotracheal Tube Model
Young Sik Park,1 Young Wook Kee,2 Kwang Suk Park,2 Jinwoo Lee,1 Sang-Min Lee,1 Jae-Joon Yim,1 Chul-Gyu Yoo,1 Young Whan Kim,1 Sung Koo Han,1 and Seok-Chul Yang1
1Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine and Lung Institute, Seoul National University College of Medicine, Seoul, Korea.
2Department of Biomedical Engineering, Seoul National University College of Medicine, Seoul, Korea.

Correspondence to Seok-Chul Yang, M.D. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine and Lung Institute, Seoul National University College of Medicine, Yeongeon-dong, Jongno-gu, Seoul 110-744, Korea. Tel: 82-2-2072-0354, Fax: 82-2-762-9662, Email: scyang@snu.ac.kr
Received May 23, 2011; Revised June 17, 2011; Accepted June 20, 2011.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.


Abstract

Background/Aims

Complete endotracheal tube obstruction is a medical emergency, and partial occlusion causes increased breathing rates and failure to wean off mechanical ventilation. Partial occlusion may be underestimated due to the lack of proper detection methods. We tested whether the sound of an endotracheal tube could be used to detect an endotracheal tube obstruction using an in vitro model.

Methods

An endotracheal tube was connected to a ventilator on one end and a test lung on the other. Sounds were recorded with a microphone located inside the endotracheal tube via a connector. During mechanical ventilation, we changed the endotracheal tube internal diameter from 5.0 to 8.0 mm and different grades of obstruction at different sites were used along the tube. Sound energy was compared among the different conditions.

Results

The energy of endotracheal tube sounds was positively correlated with the internal diameter and negatively correlated with the degree of obstruction. The rate of decline in energy differed with obstruction location. When the obstruction was more distal, the rate of decline in endotracheal sound energy was more rapid.

Conclusions

Changes in the sound of an endotracheal tube can be used to detect an obstruction. Further studies are needed for clinical application.

Keywords: Intubation, intratracheal, Sound, Airway obstruction.
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