Peripheral microcirculatory exploration during mechanical ventilation weaning

Weaning from mechanical ventilation is a daily challenge in intensive care patients. Our objective was to explore microcirculatory perfusion during mechanical ventilation weaning and to evaluate its predictive value on the weaning outcome.Prospective observational study. All consecutive patients, older than 18 years, under mechanical ventilation that met the criteria for weaning were enrolled. Patients underwent a T-piece Spontaneous Breath Trial (SBT) for 60 minutes and the usual clinical parameters were recorded every 5 minutes. Microcirculatory perfusion was evaluated using the mottling score and the Tissue Oxygen Saturation (StO2) measured by Near Infrared Spectroscopy technology on the thenar and knee area.Seventy-three patients were studied (age: 67±15 years, men: 40, SAPS II: 47±15) after a duration of mechanical ventilation of 3 (1-6) days. Forty-five patients succeeded the first SBT. The mottling score severity recorded just before ventilator disconnection (baseline) was associated with weaning failure (P=0.03). Moreover, the mottling score increase during SBT was significantly associated with weaning failure (80% vs. 28%, P=0.001; Odds ratio 10.5 [2.0-54.8]). Baseline thenar StO2 was not different according to weaning outcome (failure 76±13% vs. success 77±7%, P=0.90) whereas baseline knee StO2 was significantly lower in patients who failed the first SBT (67±13% vs. 75±12%, P0.01). This difference was apparent since the very beginning of the SBT and lasted throughout the trial (P=0.0001).In unselected mechanically ventilated patients undergoing SBT, mottling score and knee StO2 are early predictors of weaning failure.