Long-term within-subject variability of inspiratory neural drive response to hypoxia.
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.
García-Río
F
F
Servicio de Neumología, Hospital Universitario La Paz, Madrid, Spain.
Pino-García
J M
JM
Racionero
M A
MA
Terreros-Caro
J G
JG
Gómez-Mendieta
M A
MA
Prados
C
C
Villasante
C
C
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