RT Journal Article
SR Electronic
T1 Modification of concentration-response curves to inhaled methacholine after the pollen season in subjects with pollen induced rhinitis.
JF Thorax
JO Thorax
FD BMJ Publishing Group Ltd and British Thoracic Society
SP 711
OP 713
DO 10.1136/thx.49.7.711
VO 49
IS 7
A1 L Prieto
A1 M López
A1 J M Bertó
A1 A Peris
YR 1994
UL http://thorax.bmj.com/content/49/7/711.abstract
AB BACKGROUND--The effect of cessation of exposure to pollen on the concentration-response curves to inhaled methacholine was investigated. METHODS--Methacholine inhalation challenges (up to 200 mg/ml) were performed in 13 non-asthmatic patients with grass and/or Parietaria pollen-induced rhinitis during the pollen season, and one and four months after it. Concentration-response curves were characterised by their PC20, position, and plateau. RESULTS--Geometric mean methacholine PC20 increased from 6.4 mg/ml during the pollen season to 28.2 mg/ml and 54.9 mg/ml one and four months after the end of season, respectively. The mean (SE) level of the plateau decreased from 30.5 (4.3%) in the pollen season to 23.3 (3.7)% and 20.1 (3.3)% one and four months after the end of pollen season, respectively. Although the methacholine concentration that produced 50% of the maximal response increased from 2.9 mg/ml to 4.3 mg/ml and 6.0 mg/ml, the differences were not significant. CONCLUSIONS--In non-asthmatic patients with pollen-induced rhinitis cessation of exposure to pollen is associated with significant modifications in the methacholine threshold value and level of plateau, and with a small shift in the concentration-response curves to the right.