In COPD patients lung disorders causes patients to retain the carbon dioxide. This causes a state of hypercapnia. It is a state of acidosis. These patients are managed by oxygen therapy. In acute settings saturation of patients of COPD should be maintained at 88-92 %. Oxygen therapy is done in controlled manner to prevent worsening acidosis. Patients are given 24% oxygen via venturi mask at 2-3 L/min or 28% via venturi mask at 4 L/min. Check ABGs for results in 30-60 minutes after therapy. Chronic COPD patients are treated same way and if on ABGs PaCO2 is normal, oxygen supplemental should be increased to 94 to 96%. Oxygen therapy should be given as an adjunct therapy to other medications as well. Therapy should be stopped when the patient is clinically improved and ABGs support is present.