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Peak airway pressure increase is late warning sign of partial endotracheal tube obstruction whereas change in expiratory flow is an early warning sign
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Anaesthesiology and Intensive Care.
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2005 (English)In: Anesthesia and Analgesia, Vol. 100, no 3, 889-893 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2005. Vol. 100, no 3, 889-893 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:uu:diva-94024OAI: oai:DiVA.org:uu-94024DiVA: diva2:167710
Available from: 2006-02-22 Created: 2006-02-22 Last updated: 2015-06-11Bibliographically approved
In thesis
1. Evaluation of Respiratory Mechanics by Flow Signal Analysis: With Emphasis on Detecting Partial Endotracheal Tube Obstruction During Mechanical Ventilation
Open this publication in new window or tab >>Evaluation of Respiratory Mechanics by Flow Signal Analysis: With Emphasis on Detecting Partial Endotracheal Tube Obstruction During Mechanical Ventilation
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Evaluating respiratory mechanics during dynamic conditions without interrupting ongoing ventilation and flow, adds to the information obtained from the mechanics derived from static (= no flow) conditions, i.e., the flow signal has the potential to provide information on the properties of the respiratory system (including the tubing system). Hence monitoring the changes in the flow signal during ongoing mechanical ventilation would give information about the dynamic mechanics of the respiratory system. Any change in the mechanics of the respiratory system including the endotracheal tube (ETT) and the ventilatory circuit would affect the shape of the flow signal.

Knowledge of the airway pressure distal to the ETT at the carina level (= tracheal pressure) is required for calculating the extra resistive load exerted by the endotracheal tube in order to compensate for it. In a porcine model, the flow signal was used to non-invasively calculate tracheal pressure. There was good agreement between calculated and measured tracheal pressure with different modes of ventilation. However, calculation of tracheal pressure assumes that the inner diameter of the ETT is known, and this assumption is not met if the inner diameter is narrowed by secretions. Flow that passes a narrowed tube is decelerated and this is most pronounced with the high flow of early expiration, yielding a typical time constant over expiratory volume pattern that is easy to recognize during mechanical ventilation. This pattern reliably detected partial endotracheal obstruction during volume and pressure controlled mechanical ventilation.

A change in compliance of the respiratory system modifies the elastic recoil and this also affects the rate of the expiratory flow and the shape of its signal. In a porcine model, lung volume gains on the flow signal generated by the heartbeats (cardiogenic oscillations) provided information about the compliance of the respiratory system during ongoing mechanical ventilation

In conclusion analyzing the flow signal during ongoing ventilation can be a cheap, non-invasive and reliable tool to monitor the elastic and resistive properties of the respiratory system including the endotracheal tube.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 42 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 106
Keyword
Anaesthesiology and intensive care, Complication: obstructed endotracheal tube, Equipment:endotracheal tube, Heart: cardiogenic oscillation, Respiratory mechanics: respiratory mechanics, Ventilation: controlled mechanical, Anestesiologi och intensivvård
National Category
Anesthesiology and Intensive Care
Identifiers
urn:nbn:se:uu:diva-6343 (URN)91-554-6463-7 (ISBN)
Public defence
2006-03-17, Hedestrandsalen, ingång 70, Akademiska sjukhuset, Uppsala, 09:15
Opponent
Supervisors
Available from: 2006-02-22 Created: 2006-02-22Bibliographically approved

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Kawati, RafaelLichtwarck-Aschoff, Michael

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