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Long-term within-subject variability of inspiratory neural drive response to hypoxia
F García-Río1, J M Pino-García, M A Racionero
1Servicio de Neumología, Hospital Universitario La Paz, Madrid, Spain.
Study 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.
Patients And Interventions:
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.
Conclusion:
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.