A Jubran and MJ Tobin
Division of Pulmonary and Critical Care Medicine, Edward Hines Jr. Veterans Administration Hospital, Hines, IL 60141, USA.

In an accompanying article (Jubran, et al., Am. J. Respir. Crit. Care Med. 155:906-915), we report that patients with chronic obstructive pulmonary disease (COPD) who failed a trial of weaning from mechanical ventilation developed worsening of pulmonary mechanics compared with patients who tolerated the trial and were extubated. We wondered whether the greater derangements in pulmonary mechanics in the weaning failure patients are evident ever before undertaking the weaning trial. We measured mechanics of the respiratory system, lung, and chest wall during passive ventilation at usual ventilator settings in 12 patients who went on to fail a weaning trial and in 12 patients who were successfully weaned. No differences in the resistances of the respiratory system, lung, and chest wall were observed between the two groups or when the resistances were separated into the components derived from ohmic resistance and viscoelastic behavior/time-constant inhomogeneities. Likewise, the groups did not differ in terms of static elastance and dynamic intrinsic positive end-expiratory pressure (PEEPi) of the respiratory system and the respective lung and chest wall components or in terms of dynamic elastances of the respiratory system and chest wall. The failure group had a higher dynamic elastance of the lung than the success group (p < 0.01), but the individual values showed considerable overlap among the patients in the two groups so limiting its usefulness in signaling a patient's ability to sustain spontaneous ventilation. Thus, mechanics of the respiratory system and its lung and chest wall components during passive ventilation did not satisfactorily discriminate between patients who failed a weaning trial and those successfully weaned, and, thus, are unlikely to be useful in signaling a patient's ability to tolerate the discontinuation of mechanical ventilation.

This article has been cited by other articles:

				S E Cattapan, F Laghi, and M J Tobin Can diaphragmatic contractility be assessed by airway twitch pressure in mechanically ventilated patients? Thorax, January 1, 2003; 58(1): 58 - 62. [Abstract] [Full Text] [PDF]

				N. R. MacIntyre Evidence-Based Guidelines for Weaning and Discontinuing Ventilatory Support : A Collective Task Force Facilitated by the American College of Chest Physicians; the American Association for Respiratory Care; and the American College of Critical Care Medicine Chest, December 1, 2001; 120(6_suppl): 375S - 396S. [Abstract] [Full Text] [PDF]

				M. J. Tobin Advances in Mechanical Ventilation N. Engl. J. Med., June 28, 2001; 344(26): 1986 - 1996. [Full Text] [PDF]

				A. Gottschalk, M. C. Hyzer, and R. T. Geer A Comparison of Human and Machine-based Predictions of Successful Weaning from Mechanical Ventilation Med Decis Making, April 1, 2000; 20(2): 160 - 169. [Abstract] [PDF]

				A. Jubran Advances in Respiratory Monitoring During Mechanical Ventilation Chest, November 1, 1999; 116(5): 1416 - 1425. [Abstract] [Full Text] [PDF]

				S. Nava and F. Rubini Lung and chest wall mechanics in ventilated patients with end stage idiopathic pulmonary fibrosis Thorax, May 1, 1999; 54(5): 390 - 395. [Abstract] [Full Text]

				T. VASSILAKOPOULOS, S. ZAKYNTHINOS, and C. ROUSSOS The Tension-Time Index and the Frequency/ Tidal Volume Ratio Are the Major Pathophysiologic Determinants of Weaning Failure and Success Am. J. Respir. Crit. Care Med., August 1, 1998; 158(2): 378 - 385. [Abstract] [Full Text] [PDF]

				A. JUBRAN, F. LAGHI, M. MAZUR, S. PARTHASARATHY, E. R. GARRITY Jr., P. J. FAHEY, and M. J. TOBIN Partitioning of Lung and Chest-wall Mechanics Before and After Lung-volume-reduction Surgery Am. J. Respir. Crit. Care Med., July 1, 1998; 158(1): 306 - 310. [Abstract] [Full Text] [PDF]