Objectives:The objective was to describe the epidemiology of dyspnea presenting to emergency departments(EDs) in the Asia-Paci fic region, to understand how it is investigated and treated and its outcome.Methods: Prospective interrupted time series cohort study conducted at three time points in EDs in Australia,New Zealand, Singapore, Hong Kong, and Malaysia of adult patients presenting to the ED with dyspnea as amain symptom. Data were collected over three 72-hour periods and included demographics, comorbidities, modeof arrival, usual medications, prehospital treatment, initial assessment, ED investigations, treatment in the ED, EDdiagnosis, disposition from ED, in-hospital outcome, and final hospital diagnosis. The primary outcomes ofinterest are the epidemiology, investigation, treatment, and outcome of patients presenting to ED with dyspnea.Results: A total of 3,044 patients were studied. Patients with dyspnea made up 5.2% (3,105/60,059, 95%confidence interval [CI] = 5.0% to 5.4%) of ED presentations, 11.4% of ward admissions (1,956/17,184, 95%CI = 10.9% to 11.9%), and 19.9% of intensive care unit (ICU) admissions (104/523, 95% CI = 16.7% to 23.5%).The most common diagnoses were lower respiratory tract infection (20.2%), heart failure (14.9%), chronic obstructive pulmonary disease (13.6%), and asthma (12.7%). Hospital ward admission was required for 64% ofpatients (95% CI = 62% to 66%) with 3.3% (95% CI = 2.8% to 4.1%) requiring ICU admission. In-hospitalmortality was 6% (95% CI = 5.0% to 7.2%).Conclusion: Dyspnea is a common symptom in ED patients contributing substantially to ED, hospital, and ICUworkload. It is also associated with significant mortality. There are a wide variety of causes however chronicdisease accounts for a large proportion.