Alternative functional criteria to assess airflow-limitation reversibility in asthma.
BACKGROUND
International guidelines define significant bronchodilator response as absolute and percentage change from baseline in forced expiratory volume (FEV1) in the first second and/or forced vital capacity (FVC) ≥12% and 200 mL. However, bronchodilator effects on other lung function parameters have also been correlated to some degree of reversible airflow limitation.


OBJECTIVE
To determine whether changes in other lung function parameters apart from FEV1 and FVC detect functional responses to bronchodilator in asthmatic patients.


METHODS
Spirometry and body plethysmography were performed at baseline conditions and after administration of 400 μg of salbutamol by metered-dose inhaler through a space chamber device in asthmatic patients. Paired t-tests were used to compare lung function parameters between those with and without criteria for reversibility of airway obstruction according to ATS/ERS criteria. Cut-off values were obtained from the corresponding ROC curves. Measurements evaluated were FEV1, FVC, maximum mid-forced expiratory flow (FEF25-75%), residual volume (RV), inspiratory capacity (IC), airway resistance (Raw) and specific airway conductance (sGaw).


RESULTS
From a total of 100 consecutive asthmatics patients (46% of them men; average age 58.7±14.1 years; 76% with mild to moderate obstruction), 50 patients had a significant bronchodilator response. All of these had noteworthy variations (p<0.004) in PEF, FEF25-75%, RV, Raw and sGaw. The most accurate in predicting a significant bronchodilator response were the absolute and percentage improvements in PEF (≥0.4 L/s and 8%), FEF25-75% (≥0.087 L/s and 27%) and the percentage of sGaw compared with that at baseline (≥25%). Based on these cut-off values, a sizeable number of the patients defined as non-responders had important changes in airway caliber. 17 patients had significant increments in the percentage of PEF and 10 had changes in absolute volume; 6 patients had increments in percentage and 16 in absolute change of FEF25-75%; 22 patients had increments in the percentage change of sGaw.


CONCLUSIONS
Changes of FEV1 and/or FVC may underestimate significant functional response to bronchodilators in asthmatic patients with airway obstruction when considering the change in other lung function parameters.
Pulmonology Unit, Hospitais da Universidade de Coimbra, Centro Hospitalar Universitário de Coimbra, Coimbra, Portugal. Electronic address: anatavaresecastro@gmail.com.
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Tavares e Castro
Pulmonology Unit, Hospitais da Universidade de Coimbra, Centro Hospitalar Universitário de Coimbra, Coimbra, Portugal.
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Matos
Immunoallergology Unit, Hospitais da Universidade de Coimbra, Centro Hospitalar Universitário de Coimbra, Coimbra, Portugal.
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Tavares
Pulmonology Unit, Hospitais da Universidade de Coimbra, Centro Hospitalar Universitário de Coimbra, Coimbra, Portugal.
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Matos
Immunoallergology Unit, Hospitais da Universidade de Coimbra, Centro Hospitalar Universitário de Coimbra, Coimbra, Portugal.
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Segorbe-Luís
D001249:Asthma / Q000188:drug therapy* / Q000503:physiopathology*; D001993:Bronchodilator Agents / Q000627:therapeutic use*; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D012129:Respiratory Function Tests
D001993:Bronchodilator Agents
Asthma; Obstruction; Pulmonary function tests; Reversibility