title: Cardiovascular autonomic nervous system tests: determination of normative values and effect of confounding variables.
abstract: OBJECTIVE
  To determine normative values for heart rate variation to deep breathing (VAR) and Valsalva ratio (VAL) as well as the effect of various confounding variables on these measures using data from a large group of normal subjects collected from multiple centers.
  
  
  METHODS
  VAR and VAL were measured on 611 normal subjects, age range 9-79, from 63 centers and was analyzed at a single Autonomic Nervous System Reading Center. Using simple and stepwise logistic regression the effect of age, gender, height, weight, mean arterial blood pressure (MAP) and body mass index (BMI), on VAR and VAL was evaluated.
  
  
  RESULTS
  The 95% normative values range (values at 2.5 to 97.5 percentile) for VAR (n = 580) was 12.8-103.5 (mean 49.7) and for VAL (n = 425) was 1.31-2.97 (mean 1.97). No gender effect was found for either VAR or VAL (p > 0.05). VAR correlated inversely with both age and MAP, while VAL correlated inversely with both age and BMI. Since age is the principal confounding variable for both VAR and VAL, normative values are also presented stratified by age.
  
  
  CONCLUSIONS
  Normative values for VAR and VAL based on a large population sample are presented. However, the values presented may not be valid in patients with morbid obesity or malignant hypertension. These data are applicable for either individual patients or for use in multicenter research trials.
authors.affiliation: Department of Neurology, Southern Illinois University School of Medicine, Springfield 62794-9230, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: Gelber
authors.forename: M
authors.initials: M
authors.lastname: Pfeifer
authors.forename: B
authors.initials: B
authors.lastname: Dawson
authors.forename: M
authors.initials: M
authors.lastname: Schumer
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001341:Autonomic Nervous System / Q000502:physiology*; D002320:Cardiovascular Physiological Phenomena; D002648:Child; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values