The document discusses the impact of Denmark's national oxygen register on adherence to guidelines for long-term oxygen therapy (LTOT) in COPD patients. Some key findings from 1994-2000 include an increase in the prevalence and incidence of COPD patients on LTOT, more patients receiving mobile oxygen and starting LTOT after hospitalization. Documentation of hypoxemia improved but only about half of patients received follow-up and 20-25% still smoked. Survival rates increased over time but remained lower than other countries. The register data was not optimally utilized and direct feedback to doctors may help further improve LTOT guideline adherence.