Study objectives: To assess oxygen
desaturation during activities and to evaluate the short-term effects
of supplemental O2 use in patients with severe COPD who do
not qualify for long-term O2 therapy.
Design: A double-blind, randomized, placebo-controlled
Setting: Outpatients from the pulmonary
diseases division of a tertiary-care university hospital.
Patients: Twenty patients with stable COPD with
FEV1/FVC ratios of < 50%, FEV1 levels< 55% of the predicted normal value, and
Pao2 levels of > 60 mm Hg when resting.
Interventions: Patients were initially evaluated with
pulmonary function tests, blood gas analysis, and Doppler
echocardiography, and they underwent the following three 6-min walking
tests (WTs) in a random sequence: basal WT (BWT); WT while breathing
compressed air (CAWT); and WT while breathing O2
Measurements and results: The
distance walked was recorded in meters. Dyspnea was measured by Borg
scale measurement before and after the tests, and arterial oxygen
saturation measured by pulse oximetry (Spo2)
was continuously monitored. Results were analyzed by grouping patients
in the following manner: desaturators (DSs) (ie,
patients with a drop in Spo2 of at least 5%
and < 90% during the WT) vs nondesaturators (NDSs); and
O2 responders (ie, patients with an increase
of at least 10% in the distance walked and/or a decrease of at least 3
points in Borg index score) vs nonresponders. During the BWT, 11 of 20
patients (55%) were defined as desaturators. During the
O2WT, the Spo2 remained at > 90%
in every patient. The distance walked increased by 22% (p < 0.02),
and dyspnea decreased 36% (p < 0.01) in DS patients. In NDS
patients, O2 administration reduced dyspnea by 47%
(p < 0.001), but the distance walked did not improve. Responses were
markedly different from one patient to another. No significant
differences were noticed between the results of the BWT and CAWT in any
of the groups. Thirteen O2 responders did not differ
from 7 nonresponders either in basal data or in desaturation measure
during the BWT, except that all walking responders (five patients) were
above the median of basal left ventricle performance.
Conclusions: Most of the studied COPD patients desaturated
during the BWT. O2 administration avoided desaturation and
could increase the distance walked and reduce dyspnea, but these
effects were not related to walking desaturation in individual cases.
Improvements were not a placebo effect. The therapeutic role of
O2 during activities in some patients with severe COPD
needs to be individually assessed.