麻豆传媒

Stable patients with pulmonary vascular disease (PVD) tolerated travel to high altitudes fairly well with frequent monitoring and supplemental oxygen therapy provided as necessary, a field study found.

Despite the perceived risk of adverse events at high altitude, none of 27 people with pulmonary arterial hypertension (PAH) or distal chronic thromboembolic pulmonary hypertension (CTEPH) needed evacuation during a 30-hour overnight stay at Mount Säntis in the Swiss Alps -- where the elevation is 2,500 m (8,202 ft), approximating that of some communities in the Rocky Mountains.

At such high altitude, 14 of the 27 participants experienced some prespecified adverse events, according to Silvia Ulrich, MD, of University Hospital Zurich in Switzerland, and colleagues in :

• Ten participants had their oxygen saturation by pulse oximetry (SpO₂) fall below 80% for at least 30 minutes, usually at night. In these cases of severe hypoxemia, supplemental oxygen restored resting but not exercise low-altitude physiology.
• Seven people had mild headaches suggestive of acute mountain sickness. None of them wanted painkillers and only three were given supplemental oxygen.

"The results of this field study help to counsel PVD patients for [high-altitude] sojourns and call for future longer-term studies," the study authors wrote, noting that all 27 participants felt well during the study and 3 months thereafter.

Lacking more robust evidence, currently recommend that pulmonary hypertension patients with hypoxemia or exertional dyspnea or in New York Heart Association functional class ≥III avoid traveling to altitudes above 1,500 m (4,921 ft) or flying without supplemental oxygen.

"The threshold of SpO₂ desaturation which forces physicians to provide SOT [supplemental oxygen therapy] at HA [high altitude] is debated, but strongly depends on whether healthy patients are concerned. Whilst anaesthetists maintain SpO₂ >92% by routinely administering high-dose SOT, many tourists and mountaineers feel well for prolonged times at very HA with much lower SpO₂ even under strenuous exercise," Ulrich's group noted.

The investigators said they were unable to keep study participants with SpO₂ <80% at high altitude without supplemental oxygen due to ethical concerns.

Ulrich and colleagues performed a trial with a randomized-sequence, crossover design in which PVD patients were assessed in low-altitude Zurich and at high-altitude Mount Säntis, with at least a 2-week washout between study sites.

They included 27 people diagnosed with pre-capillary pulmonary hypertension who were stable on medical therapy. Within this group were 20 people with PAH (WHO group 1) whose arteries in the lungs had become narrowed, thickened, or stiff. Another seven had distal CTEPH (WHO group 4), which is characterized by undissolved blood clots in the lungs that can lead to scar tissue in the blood vessels.

Mean patient age was 62 years, and 12 of the 27 patients were women. Twenty-six patients had symptoms in functional class I/II at baseline. Mean baseline 6-minute walk distance was 580 m. Pulmonary vascular resistance was 6.5 WU on average. All patients had oxygen partial pressure exceeding 8 kPa.

During their stay on the mountain, participants had their SpO₂ and condition frequently monitored during daytime and continuously overnight. Patients with severe hypoxemia were treated with supplemental oxygen at 3 L/min via nasal cannula and had further high-altitude assessments on this therapy.

The short duration of exposure to high elevation was a limitation of the study, as was the inclusion of only central European patients, Ulrich's group acknowledged.

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