Geographic differences in use of home oxygen for obstructive lung disease: a national Medicare study.

RATIONALE Home oxygen is the most expensive equipment item that Medicare purchases ($1.7 billion/year). OBJECTIVES To assess geographic differences in supplemental oxygen use. METHODS Retrospective cohort analysis of oxygen claims for a 20% random sample of Medicare patients hospitalized for obstructive lung disease in 1999 and alive at the end of 2000. MEASUREMENTS AND MAIN RESULTS While 33.7% of the 34,916 hospitalized patients used supplemental oxygen, there was more than a 4-fold difference between states and a greater than 6-fold difference between hospital referral regions with high/low utilization. Rocky Mountain States and Alaska had the highest utilization, while the District of Columbia and Louisiana had the lowest utilization. After adjusting for patient characteristics and elevation, high-utilization communities included low-lying areas in California, Florida, Michigan, Missouri, and Washington. Patients who were younger, male, white, and who had more comorbidities, more hospital admissions, and lived at higher altitudes and in areas of greater income also had higher odds of using supplemental oxygen. Residing in rural areas was associated with higher unadjusted oxygen use rates. After adjustment, patients living in large rural areas had higher odds of using oxygen than patients living in urban areas or in small rural areas. CONCLUSIONS There is significant geographic variation in supplemental oxygen use, even after controlling for patient and contextual factors. The Centers for Medicare & Medicaid Services should examine these issues further and enact changes that ensure patient health and fiscal responsibility.