Acute respiratory distress syndrome mimickers lacking common risk factors of the Berlin definition

Some patients presenting with acute respiratory failure and meeting the Berlin criteria for acute respiratory distress syndrome (ARDS) lack exposure to common risk factors (CRF). These so-called ARDS mimickers often lack histological diffuse alveolar damage. We aimed to describe such ARDS mimickers lacking CRF (ARDS CRF-) in comparison with others (ARDS CRF+).

Retrospective study including all patients receiving invasive mechanical ventilation for ARDS admitted to the intensive care units (ICUs) of two tertiary care centers from January 2003 to December 2012.

The prevalence of ARDS CRF- was 7.5 % (95 % CI [5.5-9.5]; n = 50/665). On the basis of medical history, bronchoalveolar lavage fluid cytology, and chest CT scan patterns, four etiological categories were identified: immune (n = 18; 36 %), drug-induced (n = 13; 26 %), malignant (n = 7; 14 %), and idiopathic (n = 12; 24 %). Although the ARDS CRF- patients had a lower logistic organ dysfunction score (4 [3-8] vs. 10 [6-13]; p < 0.0001) and less often shock upon ICU admission (44 vs. 80 %; p < 0.0001) than their counterparts, their overall ICU mortality rate was very high (66 % [46-74]), and the absence of CRF remained associated with ICU mortality by multivariable logistic regression analysis (adjusted OR = 2.06; 95 % CI [1.02-4.18]; p = 0.044). Among ARDS CRF- patients, the presence of potentially reversible lung lesions with corticosteroids (aOR = 0.14; 95 % CI [0.03-0.62]) was associated with ICU survival.

The absence of CRF among patients with ARDS is common and associated with a higher risk of mortality. For such atypical ARDS, a complete diagnostic workup, including bronchoalveolar lavage fluid cytology and chest CT scan patterns, should be performed to identify those patients who might benefit from specific therapies, including corticosteroids.