Sound analysis in an in vitro endotracheal tube model.
OBJECTIVE
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.
Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine and Lung Institute, Seoul National University College of Medicine, Seoul, Korea.
Young Sik
YS
Park
Young Wook
YW
Kee
Kwang Suk
KS
Park
Jinwoo
J
Lee
Sang-Min
SM
Lee
Jae-Joon
JJ
Yim
Chul-Gyu
CG
Yoo
Young Whan
YW
Kim
Sung Koo
SK
Han
Seok-Chul
SC
Yang
D000402:Airway Obstruction; D016001:Confidence Intervals; D045853:Exhalation; D006801:Humans; D066298:In Vitro Techniques; D007442:Intubation, Intratracheal; D008962:Models, Theoretical; D011175:Positive-Pressure Respiration; D013223:Statistics as Topic