Ultrasound-assessed diaphragmatic impairment is a predictor of outcomes in patients with acute exacerbation of chronic obstructive pulmonary disease undergoing noninvasive ventilation

Background: Ultrasound (US) evaluation of diaphragmatic dysfunction (DD) has proved to be a reliable technique in critical care. In this single-center prospective study, we investigated the impact of US-assessed DD on noninvasive ventilation (NIV) failure in patients with acute exacerbations of chronic obstructive pulmonary disease (AECOPD) and its correlation with the transdiaphragmatic pressure assessed using the invasive sniff maneuver (Pdi sniff). Methods: A population of 75 consecutive patients with AECOPD with hypercapnic acidosis admitted to our respiratory intensive care unit (RICU) were enrolled. Change in diaphragm thickness (Delta Tdi) < 20% during tidal volume was the predefined cutoff for identifying DD+/-status. Correlations between Delta Tdi < 20% NIV failure and other clinical outcomes were investigated. Correlation between Delta Tdi and Pdi sniff values was analyzed in a subset of ten patients. Results: DD+ patients had a higher risk fTor NIV failure than DD-patients (risk ratio, 4.4; p < 0.001), and this finding was significantly associated with higher RICU, in-hospital, and 90-day mortality rates; longer mechanical ventilation duration; higher tracheostomy rate; and longer RICU stay. Huge increases in NIV failure (HR, 6.2; p < 0.0001) and 90-day mortality (HR, 4.7; p = 0.008) in DD+ patients were found by Kaplan-Meier analysis. Delta Tdi highly correlated with Pdi sniff (Pearson's r = 0.81; p = 0.004). Delta Tdi < 20% showed better accuracy in predicting NIV failure than baseline pH value and early change in both arterial blood pH and partial pressure of carbon dioxide following NIV start (AUCs 0.84 to DTdi < 20%, 0.51 to pH value at baseline, 0.56 to early change in arterial blood pH following NIV start, and 0.54 to early change in partical pressure of carbon dioxide following NIV start, respectively; p < 0.0001). Conclusions: Early and noninvasive US assessment of DD during severe AECOPD is reliable and accurate in identifying patients at major risk for NIV failure and worse prognosis.