Temporal Nomenclature and Definitions for Prolonged Course ARDS

ARDS affects > 20% of critically ill, mechanically ventilated patients and carries a high mortality rate. A prolonged course of ARDS is associated with high health care costs and extended ICU admission. It exhibits considerable heterogeneity in cause, biological characteristics, and chronology. ARDS criteria are subject to continuous revision by expert consensus. Expert consensus has not provided a clear definition of a prolonged course of ARDS (ie, persistent or nonresolving). What nomenclature and time-based definitions have been used in the ARDS literature over the past 3 decades to describe patients with a prolonged course of ARDS? We conducted a scoping review to assess the definitions used for a prolonged course of ARDS. PubMed and EMBASE databases were searched using a predefined and preregistered search string. We included 66 articles and found marked heterogeneity in nomenclature and definitions. Fifteen different nomenclatures were used with time frames ranging from 30 minutes to several weeks. This heterogeneity persisted across periods of the existing consensus criteria (American-European Consensus Conference vs the Berlin definition) and research topics (ie, pharmacology or biomarkers). The most common nomenclatures were persistent (n = 26 [39%]) and late (n = 26 [39%]), with the most frequent time definition being 7 days after onset of ARDS (n = 28 [42%]). The relative paucity of studies found using a comprehensive search strategy and the use of heterogeneous definitions preclude adequate meta-analyses required to gain insight into the cause, outcomes, and possible interventions aimed at improving patient care. A focused discussion is required to create a consensus definition for a prolonged course of ARDS to standardize research efforts toward improving patient outcomes.