Right-to-left shunts in lowlanders with COPD traveling to altitude: a randomized controlled trial with dexamethasone

Abstract

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 ([Formula: see text]) >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, [Formula: see text] 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.

Effect of Nocturnal Oxygen Therapy on Daytime Pulmonary Hemodynamics in Patients With Chronic Obstructive Pulmonary Disease Traveling to Altitude: A Randomized Controlled Trial

“…However, according to our previous publication from the current trial, NOT had a positive effect on various sleep measures, but not on daytime exercise capacity, blood gases, or cognitive performance compared with placebo at altitude ( Tan et al, 2020 ). Echocardiographic right-to-left shunt measurements were not performed during this study, but from previous trials, it is known that hypobaric hypoxia induces a higher prevalence of intracardiac and intrapulmonary right-to-left shunts in lowlander COPD patients traveling to altitude ( Lichtblau et al, 2020 ); and therefore, patients with COPD and right-to-left shunt might even less profit from supplemental oxygen. On the contrary, Lovering et al (2008) have demonstrated prevention of exercise-induced intrapulmonary shunts in healthy humans with high levels of hyperoxia (100% FiO 2 ).…”

“…Recommendations for altitude sojourns in COPD patients are lacking; meanwhile, several studies on COPD patients and altitude travel have been conducted (Furian et al, 2018b(Furian et al, ,c, 2019Muralt et al, 2018;Latshang et al, 2019;Lichtblau et al, 2019aLichtblau et al, ,b, 2020Schwarz et al, 2019;Tan et al, 2020;Carta et al, 2021). It is known that patients with COPD may suffer from hypoxemia when traveling to altitude and that altitude travel increases PAP, induces the occurrence of intracardiac and intrapulmonary right-to-left shunts, and reduces exercise capacity (Furian et al, 2018a,b;Lichtblau et al, 2018Lichtblau et al, , 2019bLichtblau et al, , 2020Latshang et al, 2019;Schwarz et al, 2019).…”

“…During flights, a partial pressure of oxygen (PaO 2 ) of at least 50 mmHg should be maintained, and patients with an oxygen saturation (SpO 2 ) above 95% at rest and SpO 2 > 84% during the 6-min walking test at sea level are usually able to travel without supplemental oxygen. Recommendations for altitude sojourns in COPD patients are lacking; meanwhile, several studies on COPD patients and altitude travel have been conducted ( Furian et al,2018b,c , 2019 ; Muralt et al, 2018 ; Latshang et al, 2019 ; Lichtblau et al,2019a,b , 2020 ; Schwarz et al, 2019 ; Tan et al, 2020 ; Carta et al, 2021 ). It is known that patients with COPD may suffer from hypoxemia when traveling to altitude and that altitude travel increases PAP, induces the occurrence of intracardiac and intrapulmonary right-to-left shunts, and reduces exercise capacity ( Furian et al,2018a,b ; Lichtblau et al, 2018 , 2019b , 2020 ; Latshang et al, 2019 ; Schwarz et al, 2019 ).…”

Effects of Altitude on Chronic Obstructive Pulmonary Disease Patients: Risks and Care

“…The rise of pressure in pulmonary vascular system could also worsen right-to-left shunt and then might impair gas exchange efficacy. Prevalence of right-to-left shunt reached 75% at 3100 m in a group of 87 COPD patients [ 45 ].…”

“…A recent study by Lichtblau, whose aim was to prevent right-to-left shunt by administration of dexamethasone, has not returned a reduction of the prevalence of this trouble at 3100 m [ 45 ]. By contrast, the same team provided interesting results about effects of dexamethasone on pulmonary hemodynamics in COPD patients going to altitude [ 73 ].…”