Weaning failure is a common problem in patients who are mechanically ventilated for more
than 72 hours. Prediction of successful extubation is crucial for mechanically ventilated
(MV) intensive care patients. Prolonged intubation leads to prolonged mechanical
ventilation, which is known to have undesirable and detrimental effects. Premature
extubation, on the other hand, is associated with clinical deterioration, a second
episode of mechanical ventilation, and prolonged mechanical ventilation, resulting in
multiple adverse outcomes.
In addition, up to 20% of all Intensive Care Unit (ICU) patients fail to wean from
mechanical ventilation. Prolonged mechanical ventilation is associated with half of the
total time spent on the ICU. Improving the prediction of successful weaning provides
physicians with a mean to optimize extubation timing, while reducing the incidence of
premature extubation.
The rapid shallow breathing index (RSBI) is a parameter commonly used to predict
extubation success, next to some other clinical parameters such as consciousness level,
the ability to cough and muscle strength. The most commonly used RSBI cut-off value for
predicting save extubation incorrectly classifies 15% to 20% of patients. Which means
that those patients require another period of mechanical ventilation with possible
adverse consequences. It is therefore necessary to develop new parameters or indices
aiding in the guidance of extubation timing.
Various other parameters, such as work of breathing (WOB), transpulmonary pressure swings
(PS) and the pressure time product (PTP), which are manifestations of patient effort,
have been investigated. Although a difference in transpulmonary pressure swings during a
spontaneous breathing trial (SBT) has been linked to weaning failure, it has yet to be
determined whether transpulmonary pressure swings predict extubation success or failure.
For all these measures of effort the placement of an esophageal catheter is obligatory.
Oxygen consumption (VO2) is a direct manifestation of patient effort. It is defined as
the difference between the amount of oxygen inhaled and exhaled over a predetermined time
interval. Using end tidal oxygen (etO2) measurements and volumetric calculations, it is
feasible to track VO2 variations breath-by-breath. A change in oxygen consumption during
an SBT could be an early indicator of patient effort and failure.
The investigators hypothesize that VO2 measurement, together with indices of patient
effort, could be valuable additional parameters when estimating weaning failure or
success, and therefore, aid in the prediction of extubation success or failure.
