Diaphragm Electromyography Versus Ultrasonography in the Prediction of Mechanical Ventilation Liberation Outcome.

BACKGROUND

ICU-acquired diaphragm paresis occurs in about 25% of patients after prolonged mechanical ventilation. Diaphragm function can be evaluated via several approaches including monitoring of electrical activity of diaphragm (electromyography [EMG]) or ultrasound (US) measurements. We aimed to assess the usefulness of diaphragm EMG indices in predicting liberation outcome in comparison with diaphragm US measurements.

METHODS

We included consecutive subjects invasively ventilated for > 48 h for acute respiratory failure and who were considered ready to undergo a spontaneous breathing trial (SBT). Exclusion criteria were age < 18 y, pregnancy, tracheostomy, or patients with confirmed neuromuscular diseases. To start the SBT, we set pressure support to 0 cm H2O and PEEP to 5 cm H2O. During the initial 5 min of SBT, mean values of Δ electrical activity of the diaphragm (ΔEAdi) (EAdi peak - EAdi minimal), tidal volume (VT), and breathing frequency were measured. Neuroventilatory efficiency was calculated as VT divided by ΔEAdi. Rapid shallow breathing index was calculated as breathing frequency divided by VT. US examination of the diaphragm and assessment of diaphragmatic excursion (DE) and diaphragm thickening fraction (DTF) were recorded 30 min after initiation of SBT.

RESULTS

Twenty-four subjects were included; DTF predicted weaning failure with area under the curve 0.96 and P value < .001 with sensitivity 100% and specificity 94% for the cutoff value ≤ 15%. DE for the cutoff ≤ 1.56 cm showed sensitivity 75% and specificity 69%, whereas ΔEAdi with cutoff value ≤ 4 μV showed sensitivity 25% and specificity 100%. Neuroventilatory efficiency with cutoff value ≤ 29 mL/μV showed sensitivity 50% and specificity 81%. All 3 parameters showed nonsignificant results with area under the curve 0.73, 0.56, and 0.62 and P values .08, .65, and .34, respectively.

CONCLUSIONS

Diaphragm EMG indices were inferior to diaphragm ultrasonography in prediction of mechanical ventilation liberation outcome.