Maximal degree of airway narrowing induced by methacholine and adenosine monophosphate: relationship with the decrease in forced vital capacity.
BACKGROUND
Changes in forced vital capacity (FVC) may represent an indirect method for the detection of plateau in response to inhaled bronchoconstrictor agents.


OBJECTIVE
To determine the relationship between the level of plateau obtained with either methacholine or adenosine monophosphate (AMP) and the decrease in FVC induced by each bronchoconstrictor agent.


METHODS
Airway responsiveness to high concentrations of methacholine and AMP was determined in patients with intermittent asthma (n = 41) or allergic rhinitis (n = 26). Furthermore, allergen-induced changes in the response to each bronchoconstrictor agent were investigated in 18 pollen-sensitive patients. Concentration-response curves were characterized by the slope of the FVC values recorded at each step of the challenge against the corresponding forced expiratory volume in 1 second (FEV1) values and, if possible, by the level of plateau.


RESULTS
The slope FVC vs FEV1 was similar in patients with plateau and in those without plateau. In patients with pollen allergy, the mean (95% confidence interval) for the level of plateau detected with methacholine increased from 16.8% (11.8%-22.0%) before the pollen season to 21.7% (14.8%-28.6%, P = .008) during the pollen season, whereas pollen-induced changes in the slope FVC vs FEV1 were not significant. Similar results were obtained with AMP.


CONCLUSIONS
In patients with allergic rhinitis or intermittent asthma, methacholine or AMP-induced changes in FVC are not significantly related to the presence or level of plateau. Furthermore, these 2 constituents of the concentration-response curve can be modified independently by a proinflammatory stimulus. These results suggest that the bronchoconstrictor-induced change in FVC cannot be used as a surrogate estimation of the level of plateau.
Universidad de Valencia, Valencia, Spain. prieto_jes@gva.es
Luis
L
Prieto
Victoria
V
Lopez
Carmen
C
Perez-Frances
Julio
J
Marin
D000249:Adenosine Monophosphate; D000328:Adult; D001249:Asthma / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology*; D016535:Bronchial Hyperreactivity / Q000139:chemically induced; D001985:Bronchial Provocation Tests / Q000379:methods; D016084:Bronchoconstriction / Q000187:drug effects*; D016085:Bronchoconstrictor Agents; D005260:Female; D006801:Humans; D008297:Male; D016210:Methacholine Chloride; D008875:Middle Aged; D011058:Pollen / Q000009:adverse effects; D012221:Rhinitis, Allergic, Perennial / Q000175:diagnosis* / Q000209:etiology; D014797:Vital Capacity
D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride; D000249:Adenosine Monophosphate