The Science Journal of the American Association for Respiratory Care
BACKGROUND: Present indicators of successful liberation from mechanical ventilation (MV) may not be accurate in patients who have received prolonged MV. Patients who successfully complete a trial of spontaneous breathing are still at risk of fatiguing post extubation. We sought to determine whether changes in VCO2 may indicate decreased gas exchange and predict subsequent fatigue.
METHOD: The following data was recorded at baseline and at 5 minute intervals during CPAP utilizing a Novametrix Cosmo+ interfaced with a lap top computer. VCO2, respiratory rate, arterial saturation, and expired volumes. Data was collected for 2 hrs on stable patients.
Results: Seventeen patients underwent a trial of spontaneous breathing and were included in this study. The median duration of MV prior to the study was 18 days. Respiratory failure was secondary to multiple trauma in 10 patients and followed emergency or elective surgical procedures in the other 7. The following comparisons are between the 7 patients successfully liberated within 24 hours and the 10 were not. The duration of MV prior to being studied was not different between the 2 groups. Standard weaning parameters, including the spontaneous respiratory rate, Pmax, minute ventilation and RSBI were not different between those successfully liberated within 24 hours and those who were not. VCO2 prior to starting the trial was not different between those successfully liberated and those who were not (213±60 vs. 234±48 respectively). As indicated in the figure, VCO2 decrease to a significantly greater degree in patients who were not successfully liberated within 24 hours. The results of the trail were not known prior to extubation.
Conclusions: A decreasing VCO2 during a trial of spontaneous breathing may indicate deteriorating gas exchange and fatigue. The preliminary data presented suggest that monitoring VCO2 during a trial of spontaneous breathing may be helpful in determining who will be successfully liberated from MV and aid in the decision to extubate or continue with gradual reduction in support.
(See Original for Figure)