medwireNews: Researchers show that patients with asthma experience a moderate loss of asthma control and increased neutrophilic airway inflammation on exposure to high altitude.
And the study, in which 18 asthma patients ascended the 6965 m peak of the Aconcagua mountain in Argentina, revealed that these changes could be reproduced solely by 24-hour exposure to cold air, suggesting that low temperature is the main cause of these effects at altitude.
"Nevertheless, most of the patients with asthma were able to climb to high altitude (>5000 m) and only one patient experienced a severe asthma exacerbation," say authors Lieven Dupont (KU Leuven, Belgium) and colleagues.
"As a result, we feel that climbing to high altitude should not be considered as a contradiction for patients with asthma who are well-controlled and who take appropriate preparatory measures."
The team found that there was only a moderate increase in asthma symptoms and medication use during the expedition, with the daily asthma symptom score rising from a mean of 0.2 at 750 m to 0.8 at 6000 m, and an increase in rescue medication use between 5600 and 6000 m.
However, in the expedition group, who mainly had well-controlled asthma, there was a significant increase in airway inflammation during the ascent, with sputum neutrophil percentages rising 15.2% and median myeloperoxidase levels rising fourfold. These changes were accompanied by increases in interleukin (IL)-17A and IL-5 messenger RNA levels.
And, forced expiratory volume in 1 second (FEV1) and forced vital capacity were also compromised at altitude, decreasing by a maximum of 12.3% and 18.9%, respectively, at 4300 m.
But the authors noted that in a 24-hour cold exposure test prior to the expedition, similar changes in FEV1 were observed, as were increased sputum neutrophil and IL levels.
Writing in Thorax, the authors therefore "hypothesize that the combination of cold air… and high ventilation rate may feature as the most important contributing factor in provoking airway obstruction and inflammation [at high altitude]."
They conclude that patients with well-controlled asthma can travel to high altitude. However, given the potential of cold temperatures to stimulate airway inflammation and the risk for acute exacerbation, close follow up is advised.
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