Weaning ventilator support in critically ill patients is crucial. Both delayed extubation and unexpected early reintubation are harmful to the patients. Weaning parameters and spontaneous breathing trial are used to investigate the indication and predict the successful extubation. Hemodynamic stability and physical reserve are important indicators as well. Microcirculation parameters are known to be more sensitive to the change of hemodynamic status than macrocirculation parameters. We hypothesize that the change of sublingual microcirculation before and after spontaneous breathing trial is different between the the patients with successful extubation and the patients with failed extubation. Thus, this study measures sublingual microcirculation in patients receiving spontaneous breathing trial and record the extubation status (successful or failed). The microcirculation parameters before and after spontaneous breathing trial are compared between the the patients with successful extubation and the patients with failed extubation.

Inclusion Criteria:

• critically ill patients received ventilator longer than 12 hours
• ready for spontaneous breathing trial
• GCS coma score equal or higher than 8

Exclusion Criteria:

• aged less than 20 years
• patient with tracheostomy
• patient and patients' relatives are non-native speakers

Critically ill patients who are ready for weaning ventilator support and receive spontaneous breathing trial.

The data that support the findings of this study will be available from the corresponding author upon reasonable request and approval of the research ethic committee.