A total of 43 severely ill COPD patients already on 24 h, or near 24 h, per day supplemental O2 were randomly assigned to transtracheal oxygen delivery (n = 22) or usual delivery of O2 by nasal cannula or face mask (n = 21). A few important changes were found in pulmonary function over time such as decreases of PEFR, FEF and MVV for both experimental and control groups, and FEV1% and FEV3% in experimental patients. At the same time, there was a significant decrease in both hematocrit and hemoglobin, and per cent shunting for the experimental group and a significant increase in per cent shunting in the control group. Physical, social and psychologic assessments showed significant improvement over time for experimental patients and declines for the control group. Lastly, medical costs were positively affected, as fewer days were spent in hospital post-study enrollment by experimental than control groups, and post-enrollment relative to pre-enrollment by experimental patients.