Role of diaphragm fatigue in weaning from mechanical ventilation

Mechanical ventilation offers essential ventilatory support during acute
respiratory failure. Unfortunately, mechanical ventilation is associated with
risks and complications and therefore, physicians aim to wean patients from the
ventilator as soon as the underlying reason for respiratory failure has
resolved. However, 20 - 30 % of intubated patients are difficult to wean from
mechanical ventilation, resulting in increased morbidity, mortality and health
care costs. The respiratory muscles drive ventilation with the diaphragm as the
most important inspiratory muscle. The capacity of the diaphragm of critically
ill patients is impaired by ICU-acquired muscle weakness. The combination of an
increased load imposed on the respiratory muscles and a reduced capacity to
generate pressure results in weaning failure. Although little discussion exists
as to whether respiratory muscles are weak in critically ill patients, the
development of muscle fatigue during a failed weaning trial is subject of
debate. Knowing whether or not patients develop respiratory muscle fatigue
would be of major help in planning the timing of the weaning process.

The primary objective is to determine whether the diaphragm develops
contractile fatigue during a weaning trial and if this is associated with
weaning failure. Furthermore, the hypothesis whether diaphragm efficiency
(Effdi = electrical activity of the diaphragm (Edi)/ transdiaphragmatic
pressure (Pdi)) can be used as an objective predictor for weaning outcome will
be tested.

A prospective cohort pilot study in mechanically ventilated patients.

With the exception of the placement of the esophageal catheter no other
experimental interventions will be performed. Introduction of the esophageal
catheter may result in mild discomfort. No complications have been reported
with the introduction / use of this soft small bore catheter. Furthermore, in
the case that neurophysiological measurements have not been performed for
clinical reasons, this will be done so for the study purpose. Subjects have no
clinical benefits by participating in this study.