Chronic Obstructive Pulmonary Disease (COPD) (cont.)
What is 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 lungs. 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. There are now light-weight battery operated
concentrators that do not require filling. 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 prolongs the lives of these patients.
The data is less clear when applied to individuals whose oxygen level only
declines with exercise. It is certain that these patients can increase their
exercise capacity and have improved quality of life, but prolongation of life
has not clearly been demonstrated.
Next: What else is available for treating COPD? »
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