Within- and between-day reproducibility of isocapnic cold air challenges in subjects with asthma.
Eight adult subjects with asthma had isocapnic cold air challenges on 4 different days. Three consecutive tests were performed on each visit with functional recovery between tests. Subjects were asked to breathe dry cold air (-20 degrees C) for progressively increasing levels of minute ventilation (7.5, 15, 30, and 60 L/min and maximal voluntary ventilation) until a 20% fall in FEV1 had been reached or when maximal voluntary ventilation was done. FEV1 was assessed between each level. The doses of respiratory heat exchange and minute ventilation causing 10%, 15%, and 20% changes in FEV1 were interpolated from dose-response curves. The within- and between-day 95% confidence intervals based on a single determination on the loge scale varied from +/- 0.32 to 0.59 for the indices derived from respiratory heat exchange. Reproducibility of the between-day results was more satisfactory than for the corresponding within-day assessments. No significant within-day tachyphylaxis was demonstrated for these indices.
D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000503:physiopathology*; D001833:Body Temperature Regulation; D001980:Bronchi / Q000503:physiopathology*; D003080:Cold Temperature; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D013618:Tachyphylaxis; D013997:Time Factors