Question

A 62-year-old man with an 8-year history of chronic bronchitis reports to his health care 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 × 106 mL (normal 4.2 to 5.4 × 106 mL), 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.

Tasks Please address the following:

Explain the physiologic mechanisms responsible for his edema, hypertension, and elevated red blood cell count. 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. Explain why the oxygen flow rate for a person with COPD is normally titrated to maintain the arterial PO2 between 60 and 65 mm Hg.

Answer 1

The man's symptoms are likely due to complications from chronic bronchitis such as cor pulmonale, causing edema and hypertension, and a compensatory increase in red blood cell production due to chronic hypoxemia. Continuous low-flow oxygen therapy could help improve his condition by elevating PO2 and O2 saturation, alleviating physiological stress, and potentially normalizing blood cell counts while oxygen flow is carefully titrated to avoid respiratory drive depression.

Step-by-step explanation:

A 62-year-old man with chronic bronchitis is experiencing edema, hypertension, and an elevated red blood cell count. The edema is likely due to right heart failure or cor pulmonale, which occurs when the blood vessels in the lungs become narrowed, leading to increased pressure in the pulmonary arteries and right ventricle, causing fluid to accumulate in the extremities. Hypertension in this case might be due to the lung disease resulting in low oxygen levels causing the blood vessels to narrow and the heart to pump harder, thus increasing the blood pressure. The high red blood cell count (polycythemia) is a compensatory response to chronic hypoxemia; the kidneys release more erythropoietin (EPO), which stimulates the production of red blood cells to carry more oxygen to hypoxic tissues.

Continuous low-flow oxygen therapy would be beneficial in increasing the patient's arterial PO2 and O2 saturation. This will improve activity tolerance by ensuring organs and muscles receive adequate oxygen, potentially lower the blood pressure by decreasing the compensatory mechanisms for hypoxemia, and normalize the red blood cell count by reducing the hypoxic stimulus for EPO production.

In COPD patients, the oxygen flow rate is carefully titrated to maintain the arterial PO2 between 60 and 65 mm Hg because if the PO2 is too high, it can depress the respiratory drive in patients who are chronically accustomed to higher levels of carbon dioxide, potentially leading to respiratory failure.