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Methacholine inhalation challenge. Practical consequences of using duplicate spirograms after each concentration
1Sección de Alergia y Servicio de Neumología, Hospital Doctor Peset, Valencia, Spain.
Annals of Allergy
|June 1, 1993
Summary
The second spirometry reading after methacholine challenge may alter results for asymptomatic asthma and allergic rhinitis patients. This highlights the importance of consistent spirometry methods in bronchial provocation tests.
Area of Science:
- Pulmonary Medicine
- Respiratory Physiology
Background:
- Deep inspiration before bronchial provocation tests can cause transient bronchodilation.
- This effect is observed in healthy individuals and those with allergic rhinitis.
Purpose of the Study:
- To evaluate the impact of using two consecutive spirograms after each methacholine concentration on methacholine inhalation challenge outcomes.
- To determine if the choice between the first or second FEV1 measurement influences the provocative concentration (PC20).
Main Methods:
- Methacholine inhalation challenge conducted on 70 non-smoking subjects (current asthma, asymptomatic asthma, allergic rhinitis).
- Subjects inhaled PBS followed by increasing methacholine concentrations.
- Two forced vital capacity maneuvers performed 30-40 seconds apart after each aerosol inhalation.
- Dose-response curves and PC20FEV1 calculated from both the first and second spirograms.
Main Results:
- PC20FEV1 values did not significantly differ between the first and second spirograms in patients with current asthma.
- PC20FEV1 values were significantly higher from the second spirogram compared to the first in asymptomatic asthmatic patients and allergic rhinitis patients (P < .01).
- A one doubling concentration difference in PC20FEV1 was observed between the first and second spirograms in a subset of patients.
Conclusions:
- The selection of the first or second FEV1 measurement after each methacholine concentration significantly affects the PC20 values in asymptomatic asthmatic patients and patients with allergic rhinitis.
- Standardizing spirometry technique is crucial for reliable methacholine challenge results in these populations.