Fixed ventilation during tidal volume breathing bronchial challenge may improve repeatability.
Tidal breathing during bronchial challenge shows both between- and within-subject variation. A challenge protocol permitting controlled ventilation was designed in order to improve repeatability of the method. Twenty-five patients were challenged twice with an interval of 2 h. The 2 min ventilation was kept constant at each concentration administered. During the 2 min inhalation of aerosol all expired air (VE) was led through a dry gas meter and respiratory frequency was counted concomitantly. The patients were instructed to achieve the same 2 min ventilation at each dosage. All patients accomplished the two challenges without problems. A PC20 was determined by interpolation on the log dose-response curve. Repeatability was improved compared to what has been found in previous studies on adults, although statistically non-significant when compared to one study. The 95% confidence interval for PC20 based on a single determination was rather narrow, being the observed value +/- 0.58 two-fold concentration differences.
Medical Department TTA, State University Hospital, Copenhagen, Denmark.
F
F
Madsen
L
L
Frølund
N H
NH
Nielsen
U G
UG
Svendsen
B
B
Weeke
D000328:Adult; D000336:Aerosols; D001985:Bronchial Provocation Tests / Q000592:standards; D005260:Female; D005541:Forced Expiratory Volume; D006632:Histamine / Q000008:administration & dosage / Q000031:analogs & derivatives; D006801:Humans; D008297:Male; D012119:Respiration; D013990:Tidal Volume
D000336:Aerosols; D006632:Histamine