A predictive factor for patients with acute respiratory distress syndrome: CT lung volumetry of the well-aerated region as an automated method

Purpose: Acute respiratory distress syndrome (ARDS) is an acute inflammatory lung injury that frequently shows fatal outcomes. As radiographic predictive factors, some reports have focused on the region of ill-aerated lung, but none have focused on well-aerated lung. Our objective was to evaluate the relationship between computed tomography (CT) volume of the well-aerated lung region and prognosis in patients with ARDS.

Method: This retrospective observational study of a single intensive care unit (ICU) included patients with ARDS treated between April 2011 and May 2013. We identified 42 patients with ARDS for whom adequate helical CT scans were available. CT images were analyzed for 3-dimensional reconstruction, and lung region volumes were measured using automated volumetry methods. Lung regions were identified by CT attenuation in Hounsfield units (HU).

Results: Of the 42 patients, 35 (83.3 %) survived 28 days and 32 (76.2 %) survived to ICU discharge. CT lung volumetry was performed within 144.5 ± 76.6 s, and inter-rater reliability of CT lung volumetry for lung regions below -500 HU (well-aerated lung region) were near-perfect. Well-aerated lung region showed a positive correlation with 28-day survival (P = 0.020), and lung volumes below -900 HU correlated positively with 28-day survival and ICU survival, respectively (P = 0.028, 0.017). Survival outcome was better for percentage of well-aerated lung region/predicted total lung capacity ≥40 % than for <40 % (P = 0.039).

Conclusions: CT lung volumetry of the well-aerated lung region using an automated method allows fast, reliable quantitative CT analysis and potentially prediction of the clinical course in patients with ARDS.