BACKGROUND
Chronic obstructive pulmonary disease (COPD) is a leading cause
of morbidity and mortality worldwide and results in economic
and social burden (Celli 2004). The prevalence may be greatly
underestimated because COPD is usually not diagnosed until it
is clinically apparent and moderately advanced (Anto 2001; Celli
2004). In people aged 25 to 75 years in the USA, the estimated
prevalence is about 7% and it is the fourth leading cause of deathCOPDprogresses and normal oxygenation can no longer bemaintained.
Oxygen has been administered under a number of conditions.
The benefits of long-term oxygen therapy (LTOT) for
individuals with chronic resting hypoxemia are well recognized
(MRC 1981; NOTT 1980) and have been reported in a previous
Cochrane review (Crockett 2005). Oxygen has also been used to
treat those who do not have chronic resting hypoxemia but experience
hypoxemia only during exercise or activities of daily living
(ambulatory oxygen). Studies of short-term ambulatory oxygen
for COPD include single assessment studies comparing performance
during an exercise test using oxygen with performance during
an exercise test using placebo air. A recent Cochrane review
found that short-term ambulatory oxygen improves single assessment
laboratory exercise performance in people with moderate
to severe COPD (Bradley 2005). Long-term ambulatory oxygen
studies include those in which oxygen is used at home during activities
of daily living (Bradley 2005; Ram 2002). A Cochrane review
found only two studies (a total of 70 patients), one which included
patients with severe resting hypoxemia and the other with
resting normoxemia (Ram 2002). Finally, oxygen has been used
as a temporary measure for those who are moderately hypoxemic
or normoxic (during both rest and exertion) in situations such
as short-burst therapy for breathlessness, acute therapy during an
exacerbation and for exercise training.