Thenar oxygen saturation (StO₂) alterations during a spontaneous breathing trial predict extubation failure

Weaning from mechanical ventilation (MV) is a cardiovascular stress test. Monitoring the regional oxygenation status has shown promising results in predicting the tolerance to spontaneously breathe in the process of weaning from MV. Our aim was to determine whether changes in skeletal muscle oxygen saturation (StO₂) measured by near-infrared spectroscopy (NIRS) on the thenar eminence during a vascular occlusion test (VOT) can be used to predict extubation failure from mechanical ventilation.

We prospectively studied 206 adult patients with acute respiratory failure receiving MV for at least 48 h from a 30-bed mixed ICU, who were deemed ready to wean by their physicians. Patients underwent a 30-min spontaneous breathing trial (SBT), and were extubated according to the local protocol. Continuous StO₂ was measured non-invasively on the thenar eminence. A VOT was performed prior to and at 30 min of the SBT (SBT₃₀). The rate of StO₂ deoxygenation (DeO₂), StO₂ reoxygenation (ReO₂) rate and StO₂ hyperemic response to ischemia (H_AUC) were calculated.

Thirty-six of the 206 patients (17%) failed their SBT. The remainder 170 patients (83%) were extubated. Twenty-three of these patients (13.5%) needed reinstitution of MV within 24 h. Reintubated patients displayed a lower H_AUC at baseline, and higher relative changes in their StO₂ deoxygenation rate between baseline and SBT₃₀ (DeO₂ Ratio). A logistic regression-derived StO₂ score, combining baseline StO₂, H_AUC and DeO₂ ratio, showed an AUC of 0.84 (95% CI 0.74-0.91) for prediction of extubation failure.

Extubation failure was associated to baseline and dynamic StO₂ alterations during the SBT. Monitoring StO₂-derived parameters might be useful in predicting extubation outcome.