Chest
Volume 121, Issue 4, April 2002, Pages 1042-1050
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Clinical Investigations
ASTHMA
Response of Lung Volumes to Inhaled Salbutamol in a Large Population of Patients With Severe Hyperinflation

https://doi.org/10.1378/chest.121.4.1042Get rights and content

Objectives

Current criteria use FEV1 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 (ie, 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.

Design

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 μg salbutamol.

Patients

Patients with an FEV1/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). FEV1 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.

Section snippets

Patients

A retrospective analysis was performed, deriving subjects from a large (ie, > 20,000 patients) database of patients who had undergone pulmonary function testing at the pulmonary function laboratory at Kingston General Hospital between 1982 and 1998. To be eligible, the patient was required to have undergone spirometry testing and a determination of static lung volumes before and after the administration of 200 μg salbutamol. All patients with a baseline TLC of > 115% of predicted, and airways

Patient Characteristics

Nine hundred fifty-seven individual patients who had been evaluated at the pulmonary function laboratory were included in the study. Of these, 534 were men and 423 were women. The mean age was 64.7 ± 0.37 years.

Of the 957 patients, 281 were classified as SH (ie, TLC, > 133% of predicted; FEV1/FVC ratio, < 85% of predicted), and the remaining 676 patients were classified as MH. The baseline characteristics of both groups are depicted in Figure 1.

The patients in the SH group had significant

Discussion

The relevant findings of this study are as follows. In hyperinflated patients, the measurement of IC, RV, or FVC before and after bronchodilator administration identifies a response that may not be uncovered by the standard measurement of FEV1. Indeed, the inclusion of IC, RV, or FVC with FEV1 suggests that up to three quarters of these patients improve with bronchodilator therapy. The improvements in lung volumes are largely independent of changes in maximal expiratory flow rates.

This was a

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