Natural History and Trajectory of non-COVID-19 Acute Respiratory Distress Syndrome patients. An observational study for comparison to COVID-19 populations

ABSTRACT

Introduction: Previous studies on acute respiratory distress syndrome (ARDS) relate trajectories to initial degree of hypoxia1,2 Further work is required to deduce whether previous ARDS frameworks are applicable to COVID-19 ARDS patients. Objectives: How does hypoxia progression influence outcomes in non-COVID ARDS patients and does this differ from COVID-19 ARDS patients? Methods: Mechanically ventilated patients that met the Berlin ARDS Criteria1 were selected from the Medical Information Mart for Intensive Care (MIMIC) database.3 Daily blood gas and ventilatory settings were analysed, from the point of intubation to death or discharge, allowing longitudinal analysis with high granularity. Our primary outcome was how the trajectory of patients was dependent on their hypoxia progression. Secondary outcomes included how base characteristics and initial clinical parameters affect trajectory and outcomes. Comparative analysis was performed between the results of this study and a previous large COVID-19 ARDS study4 Results: 1,575 ICU admissions were included in the study. All results report this study first followed by the COVID-19 study.4 Overall survival rate was higher (70.2% vs 57.7%);less patients had initial moderate or severe hypoxia (54.5% vs 76.8%);less patients had worsening of hypoxia over the first 7 days (18.9% vs 31.8%);and more patients improved their hypoxia status (33.1% vs 23.5%). This study showed a smaller proportion of hypoxia nonresolvers compared to the COVID study (32.6% vs 57.9%). However, non-resolvers in the two studies had similar survival rates (58.6% vs 60.4%). Length of ICU stay (LOS) and duration of invasive mechanical ventilation (IMV) was significantly less in this study compared to the COVID-19 study regardless of hypoxia resolver status. Conclusions: Non-COVID ARDS patients have a more predictable natural history and trajectory compared to COVID-19 ARDs patients. Respiratory failure occurs less frequently and is quicker to resolve, resulting in a lower proportion of hypoxia non-resolvers. However hypoxia non-resolvers of both populations have similar survival outcomes. Despite this, COVID ARDS patient have much longer ICU length of stay and length of ventilation which has significant implications for provision of critical care resources. Further analysis of the impact of COVID-19 therapies on these outcomes is needed.