A 62 year-old man with an 80-year history of chronic bronchitis reports to his healthcare provider with complaints of increasing shortness of breath, ankle swelling, and a feeling of fullness in his upper abdomen. The expiratory phase of his respirations is prolonged and expiratory wheezes and crackles are heard on auscultation. His blood pressure is 160/90 mm Hg, his red blood cell count is 6.0 x 106 uL (normal 4.2 to 5.4 x 106 uL), his hematocrit is 65% (normal male value 40% to 50%), his arterial PO2 is 55 mm Hg, and his O2 saturation, which is 85% while he is resting, drops to 55% during walking exercise.

A 62 year-old man with an 80-year history of chronic bronchitis reports to his healthcare provider with complaints of increasing shortness of breath, ankle swelling, and a feeling of fullness in his upper abdomen. The expiratory phase of his respirations is prolonged and expiratory wheezes and crackles are heard on auscultation. His blood pressure is 160/90 mm Hg, his red blood cell count is 6.0 x 10⁶ uL (normal 4.2 to 5.4 x 10⁶ uL), his hematocrit is 65% (normal male value 40% to 50%), his arterial PO₂ is 55 mm Hg, and his O₂ saturation, which is 85% while he is resting, drops to 55% during walking exercise.

1. Explain the physiologic mechanisms responsible for his edema, hypertension, and elevated red blood cell count.
2. His arterial PO₂ and O₂ saturation indicate that he is a candidate for continuous low-flow oxygen. Explain the benefits of this treatment in terms of his activity tolerance, blood pressure, and red blood cell count.
3. Explain why the oxygen flow rate for persons with COPD is normally titrated to maintain the arterial PO₂between 60 and 65 mm Hg.