Ultrasound assessed Diaphragm Impairment is a Predictor of Outcomes in Acute Exacerbation of Chronic Obstructive Pulmonary Disease undergoing Non-Invasive Ventilation.

Background. Ultrasound (US) evaluation of diaphragm 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 Non Invasive Ventilation (NIV) failure in AECOPD patients and its correlation with the trans-diaphragmatic pressure assessed through invasive sniff maneuver (Pdi sniff). Methods. A population of 75 consecutive AECOPD with hypercapnic acidosis admitted in our Respiratory Intensive Care Unit (RICU) were enrolled. Change of the diaphragm thickness (ΔTdi) < 20% during tidal volume was the pre-definite cut off to identify DD+/-. Correlations between ΔTdi <20% NIV failure and other clinical outcomes was investigated. Correlation between ΔTdi and Pdi sniff values was analyzed in a subset of 10 patients. Results. DD+ had higher risk for NIV failure as compared with DD- (RR= 4.4, p<0.001) and was significantly associated with greater RICU, in-hospital and 90-day mortality rate, MV duration, tracheostomy rate, and RICU stay. A huge increase in NIV failure (HR=6.2, p< 0.0001) and 90-day mortality (HR=4.7, p=0.008) in DD+ was reported at the Kaplan-Meyer analysis. ΔTdi highly correlated with Pdi sniff (r Pearson = 0.81, p= 0.004). ΔTdi< 20% showed better accuracy in predicting NIV failure when compared to baseline pH value and early change of both arterial blood pH and pCO2 following NIV start (AUC=0.84, 0.51, 0.56, 0.54 respectively, p<0.0001). Conclusion. Early and non-invasive US assessment of DD during severe AECOPD is reliable and accurate in identifying patients at major risk for NIV failure and worse prognosis.