Patient-ventilator interaction with conventional and automated management of pressure support during difficult weaning from mechanical ventilation.

PURPOSE: Optimizing pressure support ventilation (PSV) can improve patient-ventilator interaction. We conducted a two-center, randomized cross-over study to determine whether automated PSV lowers asynchrony rate during difficult weaning from mechanical ventilation.

METHODS: Thirty patients failing the first weaning attempt were randomly ventilated for 2 three-hour consecutive periods with: 1)PSV managed by physicians (convPSV); 2)PSV managed by Smartcare® (autoPSV). These 2 periods were applied in the afternoon and overnight, for a 12-h total study time. Two independent clinicians offline analyzed ventilator waveforms to compute asynchrony index(AI).

RESULTS: AI was lower during autoPSV than during convPSV (medians[interquartile ranges] 5.1[2.6-9.5]% vs. 7.3[2.3-13.4]%, p = 0.02), without changes in the proportion of patients with AI>10%(p = 0.31). Pressure support (PS) variability was higher during autoPSV (p < 0.001), but average PS did not vary. In patients with baseline PS > 12 cmH2 O (n = 15), PS and tidal volume were lower with autoPSV (12 [10-15]cmH2 O vs. 15 [14-18]cmH2 O,p = 0.003; 7.2[6.2-8.3]ml/Kg vs. 8.2[7.1-9.1]ml/Kg, p = 0.02) and AI reduction was driven by lower tidal volume (p = 0.03). In patients with baseline PS ≤ 12 cmH2 O, AI reduction during autoPSV was mediated by increased PS variability (p = 0.04).

CONCLUSION: During difficult weaning, autoPSV improves patient-ventilator interaction by lowering tidal volume and enhancing PS variability. In expert centres, however, the size effect of the intervention appears clinically small, likely because physicians themselves adequately limit PS and tidal volume.