Aerosol therapy delivers medicines as a fine mist directly into the lungs. This allows faster action and fewer whole-body side effects. It is a key treatment for diseases such as asthma and COPD. In acute respiratory distress syndrome (ARDS), early laboratory and small clinical studies suggested that inhaled beta-2 agonists and corticosteroids might help the lungs heal by improving mucus clearance, reducing inflammation, and helping remove excess fluid. However, larger randomized trials have not shown clear clinical benefits. Therefore, major guidelines do not provide specific recommendations for aerosol use in ARDS. There are also safety concerns, including risks of low potassium levels, abnormal heart rhythms, worsening lung function, and increased healthcare costs. Despite these uncertainties, our previous study showed that aerosol therapy continues to be used widely in ARDS patients. However, that study was small and limited to one country, so the findings may not apply to other regions. To address this gap, we have designed Aero-in-ARDS, a large, multi-national, prospective observational study. This study will investigate how often aerosol therapy is used in ARDS, what types of aerosol drugs are given, and how practices differ across countries. By identifying current patterns and comparing them with existing evidence, the study aims to highlight gaps in knowledge and guide future research.