The Reply

We have read the letter from Sikri, who raised 2 questions about our article published in The American Journal of Medicine in October 2014.1Zheng C.R. Chen G.Z. Yu J. et al.Inhaled budesonide and oral dexamethasone prevent acute mountain sickness.Am J Med. 2014; 10: 1001-1009Abstract Full Text Full Text PDF Scopus (34) Google Scholar One is about the time when Lake Louise criteria were scored. Sleeping altitude may have great significance on the occurrence of acute mountain sickness. In the recommendations regarding appropriate ascent rate in published guidelines, the key issue is the rate at which the individuals increase their sleeping elevation rather than the speed with which they are walking or climbing during the day.2Luks A.M. Clinician's corner: what do we know about safe ascent rates at high altitude?.High Alt Med Biol. 2012; 13: 147-152Crossref PubMed Scopus (19) Google Scholar In our study, on the night of July 7, 2013, the sleeping altitude of the participants reached its highest point in our trial. The participants then descended 300 m during July 8, 2013. The Lake Louise score was taken in the afternoon rather than in the morning of this day for some reasons. Considering the minor change of altitude and the same sleeping altitude, we could speculate that this descent did not decrease the incidence too much. The symptoms of acute mountain sickness usually resolve within 2 to 3 days, but they could not disappear after 4 days at altitude, especially when the participants were traveling higher and higher before the Lake Louise score was taken. This is also indicated indirectly by the difference of the incidence among the 3 groups. The other question is about the high incidence of acute mountain sickness in the placebo group. Mild physical work was involved during the study period. A long car journey sometimes brings about motion sickness,3Brainard A. Gresham C. Prevention and treatment of motion sickness.Am Fam Physician. 2015; 90: 41-46Google Scholar which does share some common symptoms with acute mountain sickness, such as nausea, dizziness, and fatigue. However, the medications for the prevention or treatment of motion sickness mainly includes scopolamine and antihistamines, and sometimes benzodiazepines and serotonin agonists.3Brainard A. Gresham C. Prevention and treatment of motion sickness.Am Fam Physician. 2015; 90: 41-46Google Scholar Symptoms induced by motion sickness may affect the evaluation of acute mountain sickness, but we are sure that this influence was equally distributed in the participants. Besides, this influence could never be eliminated if the participants traveled to high altitude by car. The imperfect implementation of this study was partly due to the resource of our participants. As we have clarified in the third section of the Appendix, the participants went to high altitude not only for the study but also to fulfill tasks at altitude. To reconcile the practical difficulties and the pursuit of perfection remains an issue during clinical trials. Inevitable Acclimatization and Acute Mountain SicknessThe American Journal of MedicineVol. 129Issue 4PreviewI read the article titled “Inhaled Budesonide and Oral Dexamethasone Prevent Acute Mountain Sickness”1 with great interest. Acute mountain sickness is a self-limiting disease after acute ascent above 2500 m, and its symptoms are most pronounced after spending one night at an altitude.2 These symptoms generally subside with acclimatization on their own within 2-3 days of arrival at high altitude.3 Interestingly, all lowlander subjects in this study were exposed to acute hypobaric hypoxia twice with varying quantum: the first time on July 4, 2013 (from 650 m to 2600 m) and the second time on July 7, 2013 (from 3200 m to 4200 m). Full-Text PDF