The goal of this retrospective observational study is to learn about how respiratory support is selected and adjusted in hospitalized patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). The main questions it aims to answer are:
1. How are different respiratory support modalities selected for patients with AECOPD in real-world practice?
2. What clinical patterns are associated with escalation, de-escalation, switching, or discontinuation of respiratory support during hospitalization? Researchers will review de-identified hospital records of patients admitted with AECOPD and analyze the dynamic use of respiratory support during hospitalization, including conventional oxygen therapy, high-flow nasal cannula oxygen therapy, non-invasive ventilation, and invasive mechanical ventilation.
Participants will not receive any study-assigned intervention. The study will use existing clinical data collected during routine inpatient care and will not change diagnosis, treatment, or follow-up.