Critical Care Medicine  |   September 2018
Respiratory Muscle Effort during Expiration in Successful and Failed Weaning from Mechanical Ventilation
Author Notes
  • From the Departments of Critical Care Medicine (J.D., L.H.R., J.G.v.d.H., L.M.A.H.), Anesthesiology (D.J.), and Pulmonary Diseases (H.W.H.v.H.) and the Donders Institute for Brain, Cognition and Behaviour, Department of Neurology (J.D.), Radboud University Medical Center, Nijmegen, The Netherlands; and the Department of Intensive Care Medicine, VU University Medical Center, Amsterdam, The Netherlands (L.M.A.H.).
  • Corresponding article on page 394.
    Corresponding article on page 394.×
  • Supplemental Digital Content is available for this article. Direct URL citations appear in the printed text and are available in both the HTML and PDF versions of this article. Links to the digital files are provided in the HTML text of this article on the Journal’s Web site (www.anesthesiology.org).
    Supplemental Digital Content is available for this article. Direct URL citations appear in the printed text and are available in both the HTML and PDF versions of this article. Links to the digital files are provided in the HTML text of this article on the Journal’s Web site (www.anesthesiology.org).×
  • Submitted for publication March 22, 2017. Accepted for publication April 11, 2018.
    Submitted for publication March 22, 2017. Accepted for publication April 11, 2018.×
  • Address correspondence to Dr. Heunks: VU University Medical Center Amsterdam, Department of Intensive Care Medicine, Postbox 7057, 1007 MB Amsterdam, The Netherlands. L.Heunks@VUmc.nl. Information on purchasing reprints may be found at www.anesthesiology.org or on the masthead page at the beginning of this issue. Anesthesiology’s articles are made freely accessible to all readers, for personal use only, 6 months from the cover date of the issue.
Article Information
Critical Care Medicine / Clinical Science / Critical Care / Respiratory System
Critical Care Medicine   |   September 2018
Respiratory Muscle Effort during Expiration in Successful and Failed Weaning from Mechanical Ventilation
Anesthesiology 9 2018, Vol.129, 490-501. doi:10.1097/ALN.0000000000002256
Anesthesiology 9 2018, Vol.129, 490-501. doi:10.1097/ALN.0000000000002256
Abstract

What We Already Know about This Topic:

  • Inspiratory muscle weakness delays weaning from mechanical ventilation, but the contributions of expiratory muscles activity are less well understood.

What This Article Tells Us That Is New:

  • Twenty adult patients receiving mechanical ventilation (more than 72 h) performed a spontaneous breathing trial. Nine patients failed weaning (11 succeeded), and these patients exhibited increased effort of the expiratory muscles and impaired neuromechanical efficiency of the diaphragm but no difference in tonic activity of the diaphragm.

Background: Respiratory muscle weakness in critically ill patients is associated with difficulty in weaning from mechanical ventilation. Previous studies have mainly focused on inspiratory muscle activity during weaning; expiratory muscle activity is less well understood. The current study describes expiratory muscle activity during weaning, including tonic diaphragm activity. The authors hypothesized that expiratory muscle effort is greater in patients who fail to wean compared to those who wean successfully.

Methods: Twenty adult patients receiving mechanical ventilation (more than 72 h) performed a spontaneous breathing trial. Tidal volume, transdiaphragmatic pressure, diaphragm electrical activity, and diaphragm neuromechanical efficiency were calculated on a breath-by-breath basis. Inspiratory (and expiratory) muscle efforts were calculated as the inspiratory esophageal (and expiratory gastric) pressure–time products, respectively.

Results: Nine patients failed weaning. The contribution of the expiratory muscles to total respiratory muscle effort increased in the “failure” group from 13 ± 9% at onset to 24 ± 10% at the end of the breathing trial (P = 0.047); there was no increase in the “success” group. Diaphragm electrical activity (expressed as the percentage of inspiratory peak) was low at end expiration (failure, 3 ± 2%; success, 4 ± 6%) and equal between groups during the entire expiratory phase (P = 0.407). Diaphragm neuromechanical efficiency was lower in the failure versus success groups (0.38 ± 0.16 vs. 0.71 ± 0.36 cm H2O/μV; P = 0.054).

Conclusions: Weaning failure (vs. success) is associated with increased effort of the expiratory muscles and impaired neuromechanical efficiency of the diaphragm but no difference in tonic activity of the diaphragm.