Long-term oxygen therapy improves exercise capacity in PH
Current guidelines recommend oxygen supplementation in PH patients
Long-term oxygen improves exercise capacity in people with pulmonary arterial hypertension (PAH) or chronic thromboembolic pulmonary hypertension (CTEPH), a study suggests.
Twelve weeks of supplemental oxygen led to a significant and clinically relevant improvements in exercise capacity, as assessed with the six-minute walking distance test (6MWD), by 42 meters (about 138 feet) over the distances walked at start of the study, “Long-term oxygen therapy in precapillary pulmonary hypertension — SOPHA study,” which was published in Scientific Reports.
PH is marked by high blood pressure in the pulmonary arteries, the blood vessels that transport blood from the heart to the lungs. Precapillary PH includes PAH, where blood pressure increases due to the narrowing of pulmonary arteries, along with CTEPH, a rare form of pulmonary hypertension where blood clots block the pulmonary arteries, increasing blood pressure and reducing the amount of oxygen transported to the rest of the body.
High blood pressure in the lungs makes the heart work harder to pump blood, ultimately weakening heart muscles. People with these conditions have shortness of breath and fatigue, limiting their ability to exercise.
Current guidelines recommend oxygen supplementation in pulmonary hypertension patients, with some evidence that it improves exercise capabilities and quality of life.
Effects of oxygen therapy in PH
Whether long-term oxygen therapy would improve 6MWD, quality of life, blood flow dynamics, and disease progression in PAH or CTEPH, isn’t fully known, leading researchers to conduct SOPHA (NCT04207593), a single-center Phase 2 clinical trial in Germany, where 20 patients were randomly assigned to either 12 weeks of supplemental oxygen for 16 or more hours a day or no oxygen supplementation. The primary outcome was to determine if long-term oxygen therapy improved exercise capacity, as measured by the 6MWD.
Twelve patients had idiopathic PAH, or PAH with an unknown underlying cause, while four had PAH due to connective tissue disease. The study included three participants with CTEPH and one with portopulmonary hypertension, that is, when pulmonary hypertension occurs in the setting of portal hypertension, elevated blood pressure in the portal vein, which directs blood from the digestive tract to the liver.
Besides 6MWD improvements after long-term oxygen treatment relative to the study’s start, treated patients showed significant walking distance benefits over the control group. On average, participants receiving long-term oxygen treatment could walk 38.9 meters more (127 feet) at follow-up, whereas the controls walked 12.3 meters (40 feet) less after 12 weeks.
The researchers also reported a trend towards improvement in quality of life, particularly in physical functioning scores, among those who received long-term oxygen.
In a per-protocol analysis, which only examined data from participants who fully adhered to the protocol, significant reductions were seen in pulmonary arterial pressure in the treated group relative to the controls, as well as a trend towards a decreased heart rate.
“This study highlights the importance of [long-term oxygen therapy] in terms of exercise capacity in patients with PAH and CTEPH,” wrote the researchers, who acknowledged their study was limited by the small sample size, which didn’t let them examine how long-term oxygen treatment could have different benefits for PH patients depending on their diagnostic subtype (i.e. PAH or CTEPH). They called for larger clinical trials to study this.
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