We designed this multicenter retrospective study to appraise outcomes in immunocompromised patients with ARF. Our research group includes about seventy intensive care units in sixteen countries. Five more countries have decided to join our group starting with this study (see appendix 1). Participating centers are clinical experts in the field of critical care and are dedicated to the care of critically ill immunocompromised patients.

Inclusion criteria are:

a) adult patients

b) admitted to the ICU between January 1, 2017 and December 31, 2022

c) with acute respiratory failure (oxygen dependence >6l/min to achieve a SpO2>92 and/or respiratory rate >30/min and/or laboured breathing and/or the need for non-invasive or invasive mechanical ventilation or high-flow nasal canula;

d) with a known immunodepression (hematological malignancy (including autologous and allogeneic stem cell transplant), solid tumor requiring treatements over the last five years, solid organ transplant, immunosuppressive drugs for auto-immune or auto-inflammatory diseases, and primary immunodeficiency). Patients with isolated HIV infection are not eligible for this study.

The primary objective is mortality 90 days after ICU admission, with a specific attention to outcomes in patients with undetermined ARF etiology. Secondary objectives are the determinants of escalation from standard oxygen therapy to the ceiling of therapy, including intubation, rescue strategies to optimize oxygenation in ARDS, and ECMO. Variables will also be collected to better assess the center effect. This will be the largest cohort of immunocompromised patients with ARF. We ambition to provide updated benchmarks on the management and outcomes of these patients and identify areas for improvement in care and generate hypotheses to improve practices.