Oxygen Therapy May Ease Lung Pressure in CTEPH Before Angioplasty

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by Margarida Maia PhD |

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Oxygen therapy may help relieve lung pressure in patients with chronic thromboembolic pulmonary hypertension (CTEPH) who are about to undergo balloon pulmonary angioplasty, a procedure in which balloons are used to open blood vessels that have been chronically narrowed or blocked, according to a new study.

Researchers found a decrease in mean pulmonary arterial pressure (PAP) occurred independently of treatment with vasodilators, meaning oxygen therapy could be helpful to maximize the safety of angioplasty.

The study, “Oxygen inhalation can selectively dilate pulmonary arteries in patients with chronic thromboembolic pulmonary hypertension before balloon angioplasty,” was published in the Journal of Cardiology.

CTEPH is a rare type of pulmonary hypertension where blood clots cause a rise in blood pressure in the arteries that go from the heart to the lungs.

The current best treatment for CTEPH is pulmonary thromboendarterectomy — a surgery to remove blood clots from the pulmonary arteries. When such a surgery is not possible, balloon pulmonary angioplasty is performed. However, this procedure brings a risk of lung injury, and the severity of the injury is made worse by a high PAP.

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In people with pulmonary hypertension who have a low level of oxygen in the blood, oxygen therapy may reduce PAP. Therefore, researchers hypothesized that oxygen therapy may provide “a safe, inexpensive, and easily accessible approach” to make angioplasty safer.

To understand how oxygen therapy changes the dynamics of blood flow in patients with CTEPH, a team of researchers in Japan conducted a study (UMIN000026882) to assess blood flow at baseline, while the patients breathed ambient air, and then again after the patients received oxygen therapy. Oxygen gas was delivered through a face mask at a rate of 5 liters per minute for at least 10 minutes.

The patients were scheduled for balloon pulmonary angioplasty on another day.

The study included 52 patients with CTEPH who underwent the procedure between May 2015 and May 2017. Their mean age was 65.2 years and 41 (79%) were women. Thirty-three (63%) patients were on home oxygen therapy and 23 (44%) were receiving one or more vasodilators — medications that lower the blood pressure by relaxing and widening the arteries. The most common vasodilator used was Adempas (riociguat), given to 19 (37%) patients.

Supplemental oxygen therapy decreased mean PAP by 3.8 mmHg, or about 9.2% from baseline. As a result, pulmonary vascular resistance also decreased, by 0.8 Wood units. (Wood units measure the resistance that must be overcome to push blood from the heart’s bottom right chamber to the pulmonary arteries.)

The team also investigated if there were any factors that could predict a decrease in lung pressure. They found that the higher the mean PAP at baseline, the greater the decrease in mean PAP after oxygen therapy.

However, “it is unclear whether oxygen inhalation is less effective in patients with low baseline PAP,” the researchers wrote.

When the team compared the patients who took vasodilators with those who did not, they found no difference in the effects of oxygen therapy.

“The beneficial effect of oxygen inhalation on mean PAP was obtained regardless of the use of vasodilators,” the researchers wrote.

In terms of safety, oxygen therapy was well-tolerated, and no discomfort or side effects were reported.

Limitations of the study included the small number of patients and the fact that they were resting while receiving oxygen therapy, which could have affected the dynamics of blood flow.

“In patients with CTEPH, 5 L/min supplemental oxygen inhalation could decrease mean PAP significantly by selective pulmonary artery dilatation, regardless of the usage of vasodilators, and thus could be helpful to maximize the safety” of balloon pulmonary angioplasty, the researchers concluded.