the role of oxygen as therapy in COPD

Sufficient oxygen is a requirement for the proper function of tissues in the body. Among all individuals, including those with COPD, there is a protective mechanism in the lung that causes constriction of blood vessels in areas of the lung that have a low concentration of oxygen because they are not being ventilated well. Constriction of the blood vessels in these areas prevents blood from traveling through these poorly-ventilated parts of the lung where there can be little exchange of oxygen (and carbon dioxide). Instead, blood is diverted to other well-ventilated parts of the lung where exchange can take place. Unfortunately, although this mechanism improves the efficiency of oxygen and carbon dioxide exchange, the constriction of the blood vessels also causes the blood pressure in the lungs to rise, a condition called pulmonary hypertension. The increased pressure requires the heart to work extra hard to pump blood to the lungs, and the right side of the heart (which is the side of the heart that pumps blood to the lungs) may fail from the extra work. This often can be detected first in a patient by the presence of ankle swelling.

Oxygen from tanks or concentrators (devices that concentrate oxygen in the air) that is inhaled by patients with COPD through masks or cannulas can relax the blood vessels and decrease blood pressure in the lung. This decreases the work that the right side of the heart must perform and can improve heart failure. Newer technology allows for very light weight tanks that supply many hours of oxygen therapy. These devices increase the mobility and hence the quality of life in these COPD patients.

Oxygen requirements can vary in patients with COPD. Some require oxygen continuously while others only need oxygen with exercise or sleep. These needs are determined by measurements of oxygen levels either with an arterial blood gas (ABG) measurement or by oximetry. It is important to note that not all patients perceive their oxygen requirements correctly. Thus, some patients with COPD can have severely reduced levels of oxygen and be unaware of it. These patients may resist using oxygen; however, many scientific studies have demonstrated that using oxygen appropriately prolongs the lives of these patients.