Diaphragm electromyographic activity as a predictor of weaning failure

To compare breathing pattern descriptors and diaphragm electromyographic activity (EAdi)-derived indices obtained from a neurally adjusted ventilatory assist catheter during a spontaneous breathing trial (SBT) in patients successfully and unsuccessfully separated from the ventilator and to assess their performance as a potential marker to discriminate these two categories of patients.

Fifty-seven ready-to-wean patients were included in a prospective observational study. During a 30-min SBT (pressure support 7 cmH₂O, zero end expiratory pressure), tidal volume (V _T) and respiratory rate (RR) were obtained from the flow signal at baseline and at 3, 10, 20 and 30 min during the SBT. EAdi-derived indices were simultaneously computed: maximum of the EAdi (EAdi_max), area under the inspiratory curve of EAdi (EAdi_AUC), the difference between EAdi_max and EAdi_min (∆EAdi), EAdi_max/V _T, EAdi_AUC/V _T and ∆EAdi/V _T. Patients, successfully (success group; n = 35) and unsuccessfully (failure group; n = 22) separated from the ventilator were compared.

At baseline, the breathing pattern was similar in the two groups, whereas EAdi_max and EAdi_AUC were significantly lower in the success group (p < 0.05). In the failure group, RR and RR/V _T increased significantly during the trial, V _T decreased, whereas EAdi_max and EAdi_AUC did not change. At 3 min, the areas under the receiver operating characteristic-curve of RR/V _T and the EAdi-derived indices to predict weaning outcome were 0.83 for the rapid shallow breathing index (RSBI), 0.84 for EAdi_max/V _T , 0.80 for EAdi_AUC/V _T (0.80) and 0.82 for ∆EAdi/V _T. The coefficient of variation for V _T decreased in the failure group while that for EAdi_max remained unchanged.

EAdi-derived indices provide reliable and early predictors of weaning outcome. However, the performance of these indices is not better than the RR/V _T.