Chest
Clinical InvestigationsAirwaysAssessing the Reversibility of Airway Obstruction
Section snippets
Subjects
The study participants were 78 outpatients with chronic airflow obstruction who were referred to a pulmonary function laboratory by their family physician. Fifty patients (37 men) met the American Thoracic Society criteria for bronchial asthma and 28 patients (27 men) met the criteria for COPD.9 To enter the study, the patients were required to have an FEV1/FVC below the lower normal limit,10 not to have suffered from exacerbations in the previous month, and to be able to abstain from
Results
Under control conditions (Table 1), all patients were obstructed, with a mean (±SD) FEV1 63 ± 19% of predicted and FVC 86 ± 18% of predicted, and moderately hyperinflated (FRC 136 ± 29% of predicted). The FEV1 was slightly but significantly less in COPD patients than in asthma patients (58 ± 20% vs 67 ± 18%; p < 0.05). m30 was on average similar to p30, though their ratio (M/P) was slightly greater in asthma patients than in COPD patients (1.05 ± 0.42 vs 0.88 ± 0.24; p < 0.06).
Discussion
The FEV1 is the traditional measure for the diagnosis of COPD and detection of reversibility of airway obstruction. Normal values are well established from population-based studies and the FEV1 is quite reproducible.1 Flow at 50% of FVC and below on both MEFV and PEFV is more variable because it is sensitive to changes in the depth of inhalation3, 4, 5 and compression of intrathoracic gas during a forced expiration.12 Furthermore, normal values are not well established. Until recently,
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Bronchodilator Response in FVC Is Larger and More Relevant Than in FEV<inf>1</inf> in Severe Airflow Obstruction
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