A novel model of “phenotypes” based on set thresholds of respiratory system compliance (Crs) was recently postulated in context of Covid-ARDS. In particular, the dissociation between the degree of hypoxaemia and Crs was characterized as a distinct ARDS phenotype.
To determine if such Crs-based phenotypes existed among patients with ARDS before the COVID-19 pandemic, and to closely examine the Crs-mortality relationship.
We undertook a secondary analysis of patients with ARDS, who were invasively ventilated on controlled modes, enrolled in a large, multinational, epidemiological study. We assessed Crs, degree of hypoxaemia, and associated Crs-based phenotype patterns with their characteristics and outcomes.
MEASUREMENTS AND MAIN RESULTS
Among 1,117 ARDS patients who met inclusion criteria, the median Crs was 30 [interquartile range, 23-40] ml/cmH2O. 136 (12%) patients had preserved Crs (50 ml/cmH2O, “phenotype L”) and 827 (74%) patients had poor Crs (<40 ml/cmH2O, “phenotype H”). Compared to phenotype L, patients with phenotype H were sicker, had more comorbidities and higher hospital mortality (32% versus 45%, P<0.05). A near complete dissociation between PaO2/FiO2 and Crs was observed. Of 136 patients with phenotype L, 58 (43%) had a PaO2/FiO2 <150. In a multivariable-adjusted analysis, the Crs was independently associated with hospital mortality (adjusted odds ratio per ml/cmH2O increase, 0.988; 95% confidence interval, 0.979-0.996; P=0.005).
A wide range of Crs was observed in non-Covid ARDS. About one-in-eight patients had preserved Crs. PaO2/FiO2 and Crs were dissociated. Lower Crs was independently associated with higher mortality. The Crs-mortality relationship lacked a clear transition threshold.