Predictive value of chest tomography at early stage in moderate to severe ARDS

Background : Computed tomography (CT) is widely used in the early stages of acute respiratory distress syndrome (ARDS) for diagnose and patient management. Recent ARDS guidelines have questioned the utility of identifying ARDS subphenotype to improve prognostic and guide ventilation strategies. Excluding COVID-19 related ARDS, the predictive value of CT during the early phase of ARDS remains unclear. Methods : We performed a 7-year retrospective study on patients admitted in the medical intensive care unit (ICU) of a tertiary teaching hospital, from January 2016 to January 2023. All patients with ARDS unrelated to COVID-19 infection who underwent a chest CT scan within 48 hours of ARDS onset were included. Lung injury severity was assessed using a semi-quantitative CT severity score (CT-SS, range: 0-25 points), evaluated by two trained intensivists. The primary outcome was 90 days all-cause mortality. Secondary outcomes included 28-days mortality, duration of mechanical ventilation, and medical complications during the ICU stay. We also investigated the relationship between ventilatory variables and CT-SS. Results : We included 114 patients with moderate to severe ARDS. The median CT severity score at admission was 18 [IQR:14-22]. 58 patients (50.1%) were classified as having severe lung injury and 56 patients (49.9%) as non-severe. The 90-day all-cause mortality was 41.2% (47/114), with no significant difference in survival between the severe and non-severe CT groups (p = 0.84, log-rank test). CT severity was also not associated with the occurrence of complications during the ICU stay. Regarding ventilatory parameters, patients with a severe CT-score had significantly higher plateau pressures (26 [23-28] cmH ₂ O vs 25 [20-26] cmH ₂ O, p = 0.01) and lower static compliance (28.8 [23.1- 36.1] ml/cmH ₂ O vs 32.7 [25.8-38.3] ml/cmH ₂ O, p = 0.05). No strong correlation was observed between the CT-score and other ventilatory variables. Conclusion : We found that early assessment of CT severity in ARDS was not associated with 90-days mortality and showed no clear relationship with ventilatory impairment. Initial CT imaging did not appear to predict ICU outcomes. These findings question the utility of routine CT use in the early management of ARDS and are consistent with recent expert guidelines, which do not support its widespread use in this context.