title: Long-term within-subject variability of inspiratory neural drive response to hypoxia.
abstract: OBJECTIVE
  We analyze the within-subject variation of mouth occlusion pressure (P0.1) response to progressive isocapnic hypoxic stimulation over long time periods in normal subjects.
  
  
  METHODS
  We studied 21 healthy subjects (14 male and 7 female; aged 40+/-12 yrs) (mean+/-SD). Lung volumes, basal P0.1, and P0.1 response to hypoxia were measured on two separate occasions 2 months apart, under similar ambient and clinical conditions.
  
  
  RESULTS
  There was no significant change in clinical condition, FVC, FEV1, arterial oxygenation saturation, end-tidal and mixed venous PCO2 levels, or P0.1 between the two visits. The mean P0.1 responses to hypoxia in the two explorations were 0.032+/-0.022 and 0.034+/-0.022 kPa/%, respectively. There was a moderate intrasubject variability of P0.1 response to hypoxia, with a coefficient of reproducibility of 0.01 kPa/%. Power calculations to establish the optimal sample size required for hypoxic stimulation are presented.
  
  
  CONCLUSIONS
  Long term within-subject variability of P0.1 response to hypoxia is moderate. This intrinsic variability needs to be emphasized when interpreting the effects of experimental interventions on hypoxic sensitivity.
authors.affiliation: Servicio de Neumología, Hospital Universitario La Paz, Madrid, Spain.
authors.forename: F
authors.initials: F
authors.lastname: García-Río
authors.forename: J M
authors.initials: JM
authors.lastname: Pino-García
authors.forename: M A
authors.initials: MA
authors.lastname: Racionero
authors.forename: J G
authors.initials: JG
authors.lastname: Terreros-Caro
authors.forename: M A
authors.initials: MA
authors.lastname: Gómez-Mendieta
authors.forename: C
authors.initials: C
authors.lastname: Prados
authors.forename: C
authors.initials: C
authors.lastname: Villasante
mesh_terms: D000328:Adult; D000399:Air Pressure; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D009055:Mouth / Q000502:physiology; D015203:Reproducibility of Results; D012119:Respiration / Q000502:physiology*; D012125:Respiratory Center / Q000502:physiology*; D012129:Respiratory Function Tests