Baseline Oxygen Saturation Predicts Exercise Desaturation Below Prescription Threshold in Patients With Chronic Obstructive Pulmonary Disease
Mark T. Knower, MD;
Donnie P. Dunagan, MD;
Norman E. Adair, MD;
Robert Chin, Jr, MD
Arch Intern Med. 2001;161:732-736.
Background Recent studies of exercise-induced hypoxemia in patients with chronic
obstructive pulmonary disease (COPD) have shown that oxygen supplementation
during exertion increases exercise tolerance and alleviates dyspnea. Although
measurements of forced expiratory volume in 1 second and diffusion capacity
for carbon monoxide (DLCO) are known to predict exercise-induced desaturation
in patients with COPD, baseline oxygen saturation has never been studied as
a predictor of exercise-induced desaturation.
Methods A retrospective analysis was performed of 100 consecutive patients with
forced expiratory volume in 1 second–forced vital capacity ratio of
70% or less who underwent exercise testing for desaturation. Any desaturation
to 88% or less with exercise was considered significant. Nineteen patients
with total lung capacity of 80% or less were excluded to avoid evaluating
those with combined obstructive and restrictive defects; 81 patients remained
available for study.
Results Nineteen (51%) of 37 patients with resting saturation of 95% or less
desaturated with exercise as opposed to 7 (16%) of 44 with resting saturation
of 96% or greater (P = .001). The sensitivity and
the negative predictive value of baseline saturation of 95% or less as a screening
test for exercise desaturation were 73% and 84%, respectively. If all patients
with DLCO of 36% or less were excluded, 40 patients were left for study. Eight
(40%) of 20 patients with baseline saturation of 95% or less compared with
0 of 20 with resting saturation of 96% or greater desaturated with exercise
(P = .006). In this subset, the sensitivity and the
negative predictive value of baseline saturation of 95% or less as a screening
test for exercise desaturation both improved to 100%.
Conclusions In patients with COPD, baseline saturation of 95% or less is a good
screening test for exercise desaturation, especially in patients with DLCO
greater than 36%. This readily available office screening procedure merits
further study in larger prospective patient cohorts.
From the Section on Pulmonary and Critical Care, Department of Internal
Medicine, Wake Forest University Baptist Medical Center, Winston-Salem, NC.
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