Conclusion: IncreasedWOBtotmaybemisinterpreted as a patientfailure (ie,tachypnea)and weaninghalted or extubation not done, prolonging intubation. The.
Elevated Imposed Work of Breathing Masquerading as Ventilator Weaning Intolerance Orlando C. Kirton, C. Bryan DeHaven, Joseph P. Morgan, Jimmy Windsor and Joseph M. Civetta Chest 1995;108;1021-1025 DOI 10.1378/chest.108.4.1021
The online version of this article, along with updated information and services can be found online on the World Wide Web at: http://chestjournal.org/cgi/content/abstract/108/4/1021
CHEST is the official journal of the American College of Chest Physicians. It has been published monthly since 1935. Copyright 2007 by the American College of Chest Physicians, 3300 Dundee Road, Northbrook IL 60062. All rights reserved. No part of this article or PDF may be reproduced or distributed without the prior written permission of the copyright holder (http://www.chestjournal.org/misc/reprints.shtml). ISSN: 0012-3692.
Downloaded from chestjournal.org on March 24, 2008 Copyright © 1995 by American College of Chest Physicians
Work of Breathing Imposed as Ventilator Weaning Masquerading Intolerance* Elevated
Orlando C. Kirton, MD, FCCP; C.
Bryan DeHaven, RRT;
Jimmy Windsor, BA; and Joseph P.M. Morgan, RRT; MD Civetta, Joseph
Objective: To test the hypothesis that, if apparent ventilatoryinsufficiency observed during a weaning or preextubation trial is due to a significant contribution of imposed work of the endotracheal tube and breath¬ ing apparatus (WOBimp), and the patient's actual work of breathing (WOBphys) is not exces¬ physiologic sive, it should be possible to extubate these patients safely. Design: Prospective descriptive study. Setting: University hospital trauma intensive care unit. Patients: A total of 28 (17% of all ventilated patients) adults intubated for 48 h or longer, who developed tachypnea (40 ±9 breaths/min) but whose blood gas exchange met predefined extubation criteria, were evaluated over a 3-month period. Interventions: Using a microprocessor-based monitor (Bicore Monitoring Systems Inc, Irvine, Calif) total patient work of breathing (WOBtot) was determined by integrating the change in intraesophageal pressure with tidal volume measured with a miniature pneu¬ motachograph positioned at the airway opening. If the patient's WOBtot was equal to or greater than 0.8 J/L, WOBimp was determines! by integrating the changes in carinal pressures with tidal volume. If neither the patient's WOBtot or WOBphys was excessively greater than that of spontaneous breathing at rest (ie, 0.8 J/L), extubation was not tolerated. This is obviously an area of further investigation. We propose a method for assessing patients who
develop unexplained tachypnea during weaning or a spontaneous breathing preextubation trial. If tachyp¬ nea is present, the total and imposed work of breath¬ ing is measured. If measured total patient work or calculated physiologic work is not excessive (ie,
