Lung Contractive Change in Severe Acute Respiratory Failure Requiring Invasive Ventilation; A Comparison of Features Between Interstitial Lung Disease and Severe Infection

Abstract Background: Generally, the incidence of irreversible lung injury is considered to be higher in acute respiratory failure due to interstitial lung disease (ILD), compared to those due to severe infection. However, those sub-phenotypes, which follow irreversible lung injury, remain poorly characterized. We aimed to examine their clinical and radiological features, in patients who could not withdraw from ventilation after receiving any treatment (defined as“irreversible respiratory failure”). Methods: Retrospective study including all patients receiving CT evaluation at onset and invasive mechanical ventilation for severe infection or acute ILD, who admitted our institution from April 2013 to May 2019. Participants were divided into Infection group and ILD group according to the dominant cause, and predictors of irreversible respiratory failure were examined among those subjects. In addition, we quantitatively evaluated the changes in lung region volumes and dispersion of grand glass opacity, using automated methods. Results: 31 patients were subdivided to ILD group, whereas 139 patients were subdivided to Infection group. Significantly more subjects in ILD group developed irreversible respiratory failure (n=22; 70.9%), compared to those in Infection group (n=27; 19.4%; p<0.001). With validation of radiological features in those subjects, distinct CT findings, including lung contractive change and non-edematous lung injury (NE-LI), were found in both groups. Lung contractive change was observed with 23 subjects in ILD group (74.2%) and 7 subjects in Infection group (5.0%). Among those, >10% lung volume reduction was confirmed by CT analysis with 19 subjects in ILD group and 4 subjects in Infection group. By multivariate logistic regression analysis, the following factors were found to be strong predictors of irreversible respiratory failure; lung contractive change (odds ratio [OR]=32.6; 95% confidence interval [CI], 7.1-150), NE-LI suspicious lesion (OR=13.3; 95% CI [2.9-59]), ILD-dominant respiratory failure (OR=18.4; 95% CI, 4.3-79), multidrug-resistant bacterial- or fungal-infection (OR=6.4; 95% CI, 1.3-31). Conclusions: We demonstrated the presence of sub-phenotypes in acute respiratory failure due to ILD and severe infection, which followed an irreversible course with distinctive radiological features including lung contractive changes.