title: Detection of partial endotracheal tube obstruction by forced pressure oscillations.
abstract: Rapid airway occlusions during mechanical ventilation are followed immediately by high-frequency pressure oscillations. To answer the question if the frequency of forced pressure oscillations is an indicator for partial obstruction of the endotracheal tube (ETT) we performed mathematical simulations and studies in a ventilated physical lung model. Model-derived predictions were evaluated in seven healthy volunteers. Partial ETT obstruction was mimicked by decreasing the inner diameter (ID) of the ETT. In the physical model ETTs of different ID were used. In spontaneously breathing volunteers viscous fluid was applied into the ETT's lumen. According to the predictions derived from mathematical simulations, narrowing of the ETT's ID from 9.0 to 7.0mm decreased the frequency of the pressure oscillations by 11% while changes of the respiratory system's compliance had no effect. In volunteers, a similar reduction (10.9%) was found when 5 ml fluid were applied. We conclude that analysis of pressure oscillations after flow interruption offers a tool for non-invasive detection of partial ETT obstruction.
authors.affiliation: Section for Experimental Anesthesiology, University Hospital of Freiburg, Germany. stefan.schumann@uniklinik-freiburg.de <stefan.schumann@uniklinik-freiburg.de>
authors.forename: Stefan
authors.initials: S
authors.lastname: Schumann
authors.forename: Michael
authors.initials: M
authors.lastname: Lichtwarck-Aschoff
authors.forename: Christoph
authors.initials: C
authors.lastname: Haberthür
authors.forename: Claudius A
authors.initials: CA
authors.lastname: Stahl
authors.forename: Knut
authors.initials: K
authors.lastname: Möller
authors.forename: Josef
authors.initials: J
authors.lastname: Guttmann
mesh_terms: D000328:Adult; D000402:Airway Obstruction / Q000503:physiopathology*; D000403:Airway Resistance / Q000502:physiology; D000465:Algorithms; D003627:Data Interpretation, Statistical; D004594:Electrophysiology; D005260:Female; D006801:Humans; D007442:Intubation, Intratracheal; D008168:Lung / Q000502:physiology; D008170:Lung Compliance / Q000502:physiology; D008297:Male; D008959:Models, Neurological; D015233:Models, Statistical; D012121:Respiration, Artificial / Q000009:adverse effects*; D015656:Respiratory Mechanics; D014132:Trachea / Q000033:anatomy & histology / Q000502:physiology