Right-to-left shunts (RLS) are prevalent in patients with
chronic obstructive pulmonary disease (
COPD) and might exaggerate
oxygen desaturation, especially at altitude. The aim of this study was to describe the prevalence of RLS in patients with
COPD traveling to altitude and the effect of preventive
dexamethasone. Lowlanders with
COPD [Global Initiative for
Chronic Obstructive Lung Disease (
GOLD) grades 1-2, oxygen saturation assessed by pulse oximetry (SpO2) >92%] were randomized to
dexamethasone (4 mg bid) or placebo starting 24 h before ascent from 760 m and while staying at 3,100 m for 48 h. Saline-contrast echocardiography was performed
at 760 m and after the first night at altitude. Of 87 patients (81 men, 6 women; mean ± SD age 57 ± 9 yr, forced expiratory volume in 1 s 89 ± 22%
pred, SpO2 95 ± 2%), 39 were assigned to placebo and 48 to
dexamethasone. In the placebo group, 19 patients (49%) had RLS, of which 13 were intracardiac. In the
dexamethasone group 23 patients (48%) had RLS, of which 11 were intracardiac (P = 1.0 vs.
dexamethasone). Eleven patients receiving placebo and 13 receiving
dexamethasone developed new RLS at altitude (P = 0.011 for both changes, P = 0.411 between groups). RLS prevalence at 3,100 m was 30 (77%) in the placebo and 36 (75%) in the
dexamethasone group (P = not significant). Development of RLS at altitude could be predicted at lowland by a higher resting pulmonary artery pressure, a lower arterial partial pressure of
oxygen, and a greater
oxygen desaturation during exercise but not by treatment allocation. Almost half of lowlanders with
COPD revealed RLS near sea level, and this proportion significantly increased to about three-fourths when traveling to 3,100 m irrespective of
dexamethasone prophylaxis.NEW & NOTEWORTHY The prevalence of intracardiac and intrapulmonary right-to-left shunts (RLS) at altitude in patients with
chronic obstructive pulmonary disease (
COPD) has not been studied so far. In a large cohort of patients with moderate
COPD, our randomized trial showed that the prevalence of RLS increased from 48%
at 760 m to 75% at 3,100 m in patients taking placebo. Preventive treatment with
dexamethasone did not significantly reduce the altitude-induced recruitment of RLS. Development of RLS at 3,100 m could be predicted
at 760 m by a higher resting pulmonary artery pressure and arterial partial pressure of
oxygen and a more pronounced
oxygen desaturation during exercise.
Dexamethasone did not modify the RLS prevalence at 3,100 m.