Background: Recent studies of exercise-induced hypoxemia in patients with c
hronic obstructive pulmonary disease (COPD) have shown that oxygen suppleme
ntation during exertion increases exercise tolerance and alleviates dyspnea
. Although measurements of forced expiratory volume in 1 second and diffusi
on capacity for carl;on monoxide (DLCO) are known to predict exercise-induc
ed 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 7
0% or less who underwent exercise testing for desaturation. Any desaturatio
n to 88% or less with exercise was considered significant. Nineteen patient
s with total lung capacity of 80% or less were excluded to avoid evaluating
those with combined obstructive and restrictive defects; 81 patients remai
ned available for study.
Results: Nineteen (51%) of 37 patients with resting saturation of 95% or le
ss desaturated with exercise as opposed to 7 (16%) of 44 with resting satur
ation of 96% or greater (P=.001). The sensitivity and the negative predicti
ve value of baseline saturation of 95% or less as a screening test for exer
cise 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 desatur
ation 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 m
erits further study in larger prospective patient cohorts.