title: Fractional exhaled nitric oxide in healthy Tibetans at high altitude.
abstract: BACKGROUND
  Fractional exhaled NO (FENO) is a marker of airway inflammation. For successful use of this marker it is important to have reference ranges from different healthy populations. The aim of this study was to establish these in healthy Tibetan adults who had always lived at high altitude on the Qinghai-Tibet Plateau.
  
  
  METHODS
  The study included 145 healthy Tibetan subjects, aged 18 to 75 years, who were non-smokers. FENO was measured at a flow rate of 50 mL/s using a chemiluminescence analyzer. Residential altitude was classified as: Grade 1 (3678-3800 m), Grade 2 (3800-4200 m), or Grade 3 (>4200 m). Correlations between subject characteristics (age, sex, height, and weight), altitude, and FENO were investigated.
  
  
  RESULTS
  The geometric mean FENO (95% CI) was 15.4 (7.0, 35.0) parts per billion (ppb). The 95% upper limit of the log-transformed data was 33.0 ppb, which was slightly lower than that for Han Chinese, and much lower than in the Northwest Han population. Mean FENO values were higher in males (16.8 ppb) than females (14.3 ppb) and inversely related to altitude. Multiple linear regression analysis showed that FENO was predicted by the equation Ln (FENO)=[2.844+0.161 × sex (1 for male; 0 for female) -0.111 × altitude grade]. The residual standard deviation (SD) was 0.048, and the explanatory value was 7%.
  
  
  CONCLUSIONS
  The upper limit of FENO in healthy Tibetan adults is 33 ppb. This value can be predicted on the basis of sex and altitude.
authors.affiliation: Department of Emergency, Chinese PLA General Hospital, Beijing, China (mainland).
authors.forename: Xuewen
authors.initials: X
authors.lastname: Ren
authors.affiliation: Department of Cardiology, Beijing Shijingshan Hospital, Beijing, China (mainland).
authors.forename: Hao
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Geriatric Cardiology, Chinese PLA General Hospital, Beijing, China (mainland).
authors.forename: Heng
authors.initials: H
authors.lastname: Hong
authors.affiliation: Department of Cardiology, Jingdezhen 335 Hospital, Jingdezhen, China (mainland).
authors.forename: Huaiyu
authors.initials: H
authors.lastname: Qiao
authors.affiliation: Department of Emergency, Chinese PLA General Hospital, Beijing, China (mainland).
authors.forename: Chunyan
authors.initials: C
authors.lastname: Man
authors.affiliation: Department of Cardiology, the Chinese PLA General Hospital, Beijing, China (mainland).
authors.forename: Gang
authors.initials: G
authors.lastname: Zhao
authors.affiliation: Department of Emergency, Chinese PLA General Hospital, Beijing, China (mainland).
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.affiliation: Department of Emergency, Chinese PLA General Hospital, Beijing, China (mainland).
authors.forename: Tanshi
authors.initials: T
authors.lastname: Li
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000531:Altitude; D001944:Breath Tests; D045853:Exhalation; D005260:Female; D006262:Health; D006801:Humans; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000032:analysis*; D018609:Tibet
chemical_list: D009569:Nitric Oxide