Response of lung volumes to inhaled salbutamol in a large population of patients with severe hyperinflation.
OBJECTIVE
Current criteria use FEV(1) to assess bronchodilator responsiveness, despite its insensitivity and inability to predict improvement in symptoms or exercise tolerance. Response in lung volumes remains largely unexplored even though volume parameters, such as inspiratory capacity (IC), closely correlate with functional improvements. Therefore, we assessed the response of lung volumes (i.e., by IC, total lung capacity [TLC], functional residual capacity [FRC], residual volume [RV], and FVC) to salbutamol and the relationship of these changes to improvements in the spirometry in these patients.


METHODS
A retrospective review of data extracted from a large database of patients who were undergoing spirometry and static lung volume measurements before and after the administration of 200 microg salbutamol.


METHODS
Patients with an FEV(1)/FVC ratio of < 85% of predicted values were defined as being severely hyperinflated (SH) if TLC was > 133% of predicted and as being moderately hyperinflated (MH) if TLC was 115 to 133% of predicted.


RESULTS
Two hundred eighty-one SH patients and 676 MH patients were identified. Salbutamol significantly reduced the mean (+/- SEM) TLC (SH patients, 222 +/- 23 mL; MH patients, 150 +/- 10 mL; p < 0.001), FRC (SH patients, 442 +/- 26 mL; MH patients, 260 +/- 39 mL; p < 0.001), and RV (SH patients, 510 +/- 28 mL; MH patients, 300 +/- 14 mL; p < 0.001) and increased both the IC (SH patients, 220 +/- 15 mL; MH patients, 110 +/- 11 mL; p < 0.001) and FVC (SH patients, 336 +/- 21 mL; MH patients, 204 +/- 13 mL; p < 0.001). FEV(1) improved in a minority of patients (SH patients, 33%; MH patients, 26%), but if lung volume measurements are also considered, the overall bronchodilator response may improve to up to 76% of the SH group and up to 62% of the MH group. Changes in volumes correlated poorly with changes in maximal airflows.


CONCLUSIONS
Bronchodilators reduce hyperinflation. Measurements of lung volumes before and after bronchodilators add sensitivity when examining for bronchodilator responsiveness.
Newton
Marcus F
MF
Pulmonary Function Laboratory, Kingston General Hospital, Kingston, ON, Canada.
O'Donnell
Denis E
DE
Forkert
Lutz
L
D000368:Aged; D000403:Airway Resistance / Q000187:drug effects*; D000420:Albuterol / Q000008:administration & dosage* / Q000009:adverse effects; D001249:Asthma / Q000175:diagnosis / Q000188:drug therapy*; D001993:Bronchodilator Agents / Q000008:administration & dosage* / Q000009:adverse effects; D005260:Female; D006801:Humans; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000188:drug therapy*; D012123:Pulmonary Ventilation / Q000187:drug effects*; D012189:Retrospective Studies; D014109:Total Lung Capacity / Q000187:drug effects; D016896:Treatment Outcome
D001993:Bronchodilator Agents; D000420:Albuterol