P43 Diaphragmatic ultrasound as a marker of clinical status and early readmissions after acute exacerbations of COPD: preliminary results from a prospective cohort study

Introduction The management of acute exacerbation of COPD (AECOPD) is complicated by the lack of a specific biomarker related to clinical course and readmission/treatment failure risk. As AECOPD are characterized by an acute worsening of lung hyperinflation and increased respiratory work, which can lead to diaphragm weakness and/or fatigue, we hypothesized that the serial monitoring of diaphragm function during an AECOPD could provide clinically relevant information on the clinical status of patients and their treatment failure risk. Methods Patients with AECOPD requiring hospitalization in our center were prospectively recruited. Diaphragm thickening fraction (reported as the ratio of tidal to maximal thickening fractions of the diaphragm – TF%max) was measured using ultrasonography within 24h of admission and within 24h of discharge. The difference in TF%max value between admission and discharge was reported as ΔTF. In addition to clinical and demographic characteristics, National Early Warning Score (NEWS), COPD Assessment Test (CAT) and blood gases were retrieved at the time of admission. Treatment failure was defined as a readmission to the emergency department/hospital Results 18 patients were recruited [mean (±standard deviation) age 74±7 years, FEV139±17%, residual volume 153±69% and CAT score 26±6]. Mean TF%max decreased from 54±20% on admission to 43±19% at discharge (p=0.06). Mean ΔTF was -10±50%. 5 patients (28%) were readmitted within 30 days. In these patients, TF%max at the time of discharge and the change in TF%max during hospitalization were significantly different than in those without readmission (65±7 vs 35±16%, p=0.001 and 30±66 vs -27±35%, p=0.02, respectively) (figure 1). ΔTF was significantly correlated to length of hospital stay (rho=0.49, p=0.04), but TF%max, NEWS, CAT score and pCO2 measured on admission were not (all p>0.05). Conclusions TF%max, measured using ultrasonography, is responsive to clinical evolution during episodes of AECOPD, and may be able to predict the risk of early readmission. Further data is required to better delineate the role of diaphragm ultrasound in this setting and to identify clinically relevant threshold values associated with negative outcomes.