Characteristics and Outcomes of Diffuse Interstitial Pneumonias Discovered in the ICU: A Retrospective Monocentric Study—The “IPIC” (Interstitial Pneumonia in Intensive Care) Study

<b>Background/Objectives</b>: Interstitial lung disease (ILD) is a heterogenous group of disorders characterised by an association of inflammatory and fibrotic abnormalities of the lung. Acute respiratory failure (ARF) may represent the initial picture of the disease. This study aims to highlight the diagnosis of ILD in the intensive care unit (ICU) and to describe the epidemiological, prognostic, and imaging features of patients diagnosed for the first time with ILD in the ICU. <b>Methods</b>: We conducted a single-centre retrospective study. We screened all 2459 patients admitted to our ICU from October 2017 to February 2020. The inclusion criteria consisted of the ILD diagnosis criteria. For each patient, clinical data and lung computed tomography scan patterns were analysed. The selected cases were then reviewed by an expert team at the tertiary care teaching hospital of Marseille (Hôpital Nord, Marseille, France). <b>Results</b>: During the study period, 26 ICU patients were diagnosed with ILD and 20 cases were confirmed by the expert team. The most frequent diagnoses were idiopathic ILD (<i>n</i> = 7, 35%), auto-immune disease-related ILD (<i>n</i> = 7, 35%), exposure-related ILD (<i>n</i> = 3, 15%), and carcinomatous lymphangitis (<i>n</i> = 3, 15%). Fifteen patients were men (75%), with a mean age of 70 (62-72) years. The median SOFA score was 4 (3-7), and 16 (80%) patients received invasive mechanical ventilation. The mean ratio of the oxygen pressure to the fraction of inspired oxygen was 174 (148-198) mmHg. The ICU mortality rate of our cohort was significantly higher than the average ICU mortality (65% vs. 26%, <i>p</i> < 0.003). The mortality rate was lower among the subgroup of auto-immune disease-related ILD (57%). <b>Conclusions</b>: We conducted a single-centre cohort study of patients diagnosed with ILD in the ICU. This rare cause of ARF was associated with poor outcome in the ICU, but auto-immune disease-related ILD seemed to have a better prognosis. High-resolution lung CT and identification of lesion patterns are the cornerstones of the diagnosis. Improved knowledge of ILD and multidisciplinary discussion (MDD) involving radiologists, pneumologists, and intensivists may result in an earlier diagnosis and eventually improved treatments.