COPD affects 10% of the world’s population and is the third leading cause of death. In the U.S., COPD kills one person every four minutes. The economic burden is high: COPD costs nearly $72B a year, 40% spent on ER and hospital stays. Disease exacerbations (acute lung-function deterioration) account for most hospitalizations; half of patients admitted die within four years. If exacerbations were detected within 24 hours, ~80% could be managed in outpatient settings. Our hardware+software solution helps patients and doctors diagnose exacerbations and intervene early to reduce healthcare costs and improve patients’ quality of life.