Abstract
BACKGROUND & AIMS
It is not clear how rapid ascent to high altitude causes the gastrointestinal symptoms of acute mountain sickness (AMS). We assessed the incidence of endoscopic lesions in the upper gastrointestinal tract in healthy mountaineers after rapid ascent to high altitude, their association with symptoms, and their pathogenic mechanisms.
METHODS
In a prospective study, 25 mountaineers (10 female; mean age, 43.8y±9.5 y) underwent unsedated, transnasal esophago-gastroduodenoscopy in Zurich (490 m) and then on 2 test days (days 2 and 4) at a high altitude laboratory in the Alps (Capanna Regina Margherita, 4559 m). Symptoms were assessed using validated instruments for AMS (the AMS-C and the Lake Louise scoring system) and visual analogue scales (0-100). Levels of mRNAs in duodenal biopsies were measured by qPCR.
RESULTS
The follow-up endoscopy at high altitude was performed in 19/25 patients on day 2 and in 23/25 patients on day 4. Frequency of endoscopic lesions increased from 12% at baseline to 26.3% on day 2 and 60.9% on day 4 (P<0.001). The incidence of ulcer disease increased from 0 at baseline to 10.5% on day 2 and 21.7% on day 4 (P=.014). Mucosal lesions were associated with lower hunger scores (37.3 vs. 67.4 in patients without lesions; P=.012). Subjects with peptic lesions had higher levels of HIF2A mRNA, which encodes a hypoxia-induced transcription factor, and ICAM1 mRNA, which encodes an adhesion molecule, compared with subjects without lesions (fold changes: 1.38 vs 0.63; P=.001 and 1.37 vs 0.66; P=.011).
CONCLUSIONS
In a prospective study of 25 mountaineers, fast ascent to high altitude resulted in rapid onset of clinically meaningful mucosal lesions and ulcer disease. Duodenal biopsies from these subjects had increased levels of HIF2A mRNA and ICAM1 mRNA, which might contribute to formation of hypoxia-induced peptic lesions. Further studies are needed of the mechanisms of this process.
Fruehauf, Heiko