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  • Poster presentation
  • Open Access

Changes in microcirculation during weaning trials from mechanical ventilation

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Critical Care200610 (Suppl 1) :P319

  • Published:


  • Mechanical Ventilation
  • Respiratory Rate
  • Oxygen Saturation
  • Tissue Oxygen
  • Spontaneous Breathing


We hypothesized that a decrease in tissue oxygen saturation (StO2) could be detected in patients during weaning failure. To this end, we determined the changes in StO2 during weaning trials from mechanical ventilation using near-infrared spectroscopy (NIRS).

Patients and methods

We studied 16 consecutive, mechanically ventilated patients (age 61 ± 15 years, SOFA score 4.5 ± 1.4), whose physician had judged them ready to wean, during a 2-hour T-piece weaning trial. The weaning trial was defined as successful when the patient was able to sustain spontaneous breathing without distress. Oxygenation, respiratory rate (RR), and minute ventilation (VE) were measured before and either at 2 hours after disconnection from the ventilator in patients with successful weaning trial, or at the time of reconnection to the ventilator in those with a failed one. The thenar muscle StO2 was measured non-invasively by NIRS (InSpectra; Hutchinson Technology, USA), at the same time points, by the arterial occlusion method.


Eleven patients had successful and five had failed weaning trials. The SaO2, respiratory rate, and VE on mechanical ventilation were not different between the two groups. During the weaning trial, the SaO2 was decreased in the failure group (from 99% to 92%, P = 0.027), the RR was increased (from 20 to 43 breaths/min, P < 0.05) while the VE did not change significantly (from 11 to 12.8 l/min, P = 0.55). These variables did not change significantly in the success group. The StO2 baseline on mechanical ventilation was not different between failure and success group patients (72.8% and 78.2%, respectively). At the end of the weaning trial the StO2 baseline was decreased to 65% in failure group patients (P = 0.05), while it did not change in the success group. The StO2 decrease rate on mechanical ventilation was not different between the two groups. At the end of the weaning trial, the StO2 decrease rate was significantly lower in failure group patients compared with that of the success group (13.3 ± 2.6 vs 22.5 ± 10.9, P = 0.026).


These results indicate that microcirculation, as it is monitored by the NIRS technique, might be impaired in patients who fail to wean from mechanical ventilation. Further study is needed to define the role of this method during weaning from mechanical ventilation.

Authors’ Affiliations

Evangelismos Hospital, Athens, Greece


© BioMed Central Ltd 2006