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,
References (28)
- et al.
Partial and maximal expiratory flow-volume curves in normal and asthmatic subjects before and after inhalation of metaproterenol
Chest
(1985) Lung function testing: selection of reference values and interpretative strategies
Am Rev Respir Dis
(1991)- et al.
Effect of a previous deep inspiration on airway resistance in man
J Appl Physiol
(1961) - et al.
Partial flow-volume curves to measure bronchodilator dose-response curves in normal humans
J Appl Physiol
(1981) - et al.
Effects of increasing doses of β-agonists on airway and parenchymal hysteresis
J Appl Physiol
(1990) - et al.
Lung hyperinflation and flow limitation in chronic airway obstruction
Eur Respir J
(1997) - et al.
Use of magnetometers to volume-reference flow-volume curves
J Appl Physiol
(1980) - et al.
The use of criteria for reversibility and obstruction to define patient groups for bronchodilator trials: influence of clinical diagnosis, spirometric, and anthropometric variables
Am Rev Respir Dis
(1985) Chronic bronchitis, asthma and pulmonary emphysema
Am Rev Respir Dis
(1962)- et al.
Lung volumes and forced ventilatory flows
Report Working party Standardization of Lung Function Tests, European Community for Steel and Coal. Official Statement of the European Respiratory Society. Eur Respir J Suppl
(1993)