title: Alternations of heart rate variability at lower altitude in the predication of trekkers with acute mountain sickness at high altitude.
abstract: OBJECTIVE
  To determine the change and relationship of spectral components of heart rate variability (HRV) measurements in subjects with or without acute mountain sickness (AMS) at both low and high altitude.
  
  
  METHODS
  A prospective study.
  
  
  METHODS
  A 12-day itinerary by trekking to the Namche Bazaar, 3440 m in Nepal.
  
  
  METHODS
  A total of 32 subjects were recruited.
  
  
  METHODS
  The alternations were measured by heart rate (HR), arterial oxygen saturation (SpO(2)), and spectral analysis of HRV at sea level, 1317 m, 3440 m, 1317 m, and sea level, respectively.
  
  
  METHODS
  Spectral analysis of HRV.
  
  
  RESULTS
  There were statistically significant increases in HR and decreases in SpO(2) in all subjects at high altitude. In HRV, the values of R-R interval, total variance, high frequency (HF), low frequency (LF), and HF% were significantly lower at 3440 m than at sea level, respectively (P < 0.05). The subjects with AMS had significantly lower total variance, HF, and HF%, respectively, but higher LF:HF ratio (P < 0.05) at 3440 m. Subjects with both HF% < 20% (nu) and LF:HF ratio > 1.3 measured at 1317 m had odds ratios of 7.00 (95% confidence interval, 1.11 to 44.06; P = 0.047) to get AMS at 3440 m.
  
  
  CONCLUSIONS
  The HRV measurements in total variances, HF, and HF% in trekkers with AMS were statistically significantly lower at high altitude. HF% < 20% (nu) or LF:HF ratio > 1.3 at lower altitudes could be an important predication parameter of trekkers with AMS at higher altitudes.
authors.affiliation: Department of Emergency Medicine, Taipei Veterans General Hospital, Taipei, Taiwan, R.O.C.
authors.forename: Hsien-Hao
authors.initials: HH
authors.lastname: Huang
authors.forename: Chia-Ying
authors.initials: CY
authors.lastname: Tseng
authors.forename: Ju-Sing
authors.initials: JS
authors.lastname: Fan
authors.forename: David Hung-Tsang
authors.initials: DH
authors.lastname: Yen
authors.forename: Wei-Fong
authors.initials: WF
authors.lastname: Kao
authors.forename: Shi-Chuan
authors.initials: SC
authors.lastname: Chang
authors.forename: Terry B J
authors.initials: TB
authors.lastname: Kuo
authors.forename: Chun-I
authors.initials: CI
authors.lastname: Huang
authors.forename: Chen-Hsen
authors.initials: CH
authors.lastname: Lee
mesh_terms: D000531:Altitude; D000532:Altitude Sickness / Q000175:diagnosis* / Q000503:physiopathology; D000704:Analysis of Variance; D001341:Autonomic Nervous System; D015415:Biomarkers; D016001:Confidence Intervals; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D009051:Mountaineering; D016017:Odds Ratio; D010092:Oximetry; D010101:Oxygen Consumption; D011446:Prospective Studies; D012306:Risk
chemical_list: D015415:Biomarkers