There are a few major complications of COVID-19 when managing patients in an in-patent setting, and they can all present similarly with respiratory deterioration, so it’s important to distinguish between them.

1. Progression of the viral pneumonia, typically presenting with progressive oxygenation failure, bilateral changes to the chest x-ray (usually lymphocyte count low and decreasing with increasing CRP).
2. Secondary bacterial infection, which is difficult to distinguish between progression of the viral pneumonia. Typically, patients may have a productive cough with purulent sputum, more dense, focal changes on the chest x-ray, neutrophilia with elevated CRP and elevated pro-calcitonin >0.5 µg/l (if available).
3. Venous thromboembolic disease, typically presenting with progressive oxygenation failure but no real changes on the chest x-ray.