Nasal mucociliary transport is impaired at altitude.

There have been a number of anecdotal reports of rhinitis and nasal obstruction occurring at altitude. To quantify these reports, we investigated nasal obstruction and mucociliary transport in a group of healthy volunteers trekking to Mount Everest Base Camp, Nepal, altitude 5,300 m. Nasal obstruction was estimated by subjective scoring and mucociliary transport was determined by the saccharin method. Subjective assessment showed that nasal obstruction was increased on arrival at 5,300 m in 23 out of 54 subjects, unchanged in 24, and decreased in seven (McNemar's test: chi 2 = 7.5; p < 0.01). The median saccharin time at sea level was 11 min (95% confidence interval (95% CI) 8-17 min) and increased to 60 min (95% CI 27-60 min) on arrival at 5,300 m. Compared to sea level, the saccharin time was prolonged in 25 out of 33 subjects (McNemar's test: chi 2 = 14.7; p < 0.01), and remained prolonged after 2 weeks at altitude (median 60 min; 95% CI 38-60 min). These results confirm the subjective feelings of nasal obstruction and show that nasal mucociliary transport times are increased at altitude. The mechanisms of these findings are not clear, but nasal obstruction may impede breathing and adversely affect performance at altitude.