title: Spirometry in normal subjects in sitting, prone, and supine positions.
abstract: OBJECTIVE
  Determine whether pulmonary function testing is affected by patient positioning.
  
  
  METHODS
  In a descriptive study with measurements made in a sequential but randomized order at a university-based pulmonary function laboratory, 20 healthy men, ages 18-50 years, were evaluated with spirometric assessment of forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), and maximum voluntary ventilation (MVV) in the sitting, supine, and prone positions. Subjects were excluded for body mass index (BMI) > 30 kg/m2 or abnormal baseline spirometry.
  
  
  RESULTS
  Comparing sitting to supine and prone positions, there was a statistically significant decline in the spirometry values (reported as percent of predicted normal +/- standard error of the mean). FVC was 102% +/- 4% while sitting, 95% +/- 4% while supine, and 94% +/- 4% while prone. FEV1 was 104% +/- 3% while sitting, 96% +/- 3% while supine, and 94% +/- 3% while prone. MVV was 115% +/- 4% while sitting, 102% +/- 4% while supine, and 97% +/- 3% prone.
  
  
  CONCLUSIONS
  In healthy men with BMI < 30 kg/m2, changing from the sitting to supine or prone position results in statistically significant change in respiratory pattern. However, all spirometry values in each position were normal by American Thoracic Society definitions.
authors.affiliation: Department of Emergency Medicine, UC San Diego Medical Center 92103, USA. gmvilke@ucsd.edu
authors.forename: G M
authors.initials: GM
authors.lastname: Vilke
authors.forename: T C
authors.initials: TC
authors.lastname: Chan
authors.forename: T
authors.initials: T
authors.lastname: Neuman
authors.forename: J L
authors.initials: JL
authors.lastname: Clausen
mesh_terms: D000293:Adolescent; D000328:Adult; D006801:Humans; D008297:Male; D008875:Middle Aged; D011187:Posture / Q000502:physiology*; D012016:Reference Values; D012129:Respiratory Function Tests; D013147:Spirometry