Bronchodilator Response Assessment of the Small Airways Obstructive Pattern.

Plamen Bokov,Mohamed Essalhi,Karine Gillet-Juvin,Christophe Delclaux,Sémia Graba,Clémence Martin

doi:10.2174/1874306401711010047

Abstract

Background:A concomitant decrease in FEV1 and FVC with normal FEV1/FVC ratio and TLC defines small airways obstructive pattern (SAOP) and constitutes a classic pitfall of pulmonary-function-tests interpretation.Objective:To evaluate the prevalence of flow- (FEV1 increase≥12% and 200 mL), volume- (FVC or inspiratory capacity [IC] increase≥12% and 200 mL), flow and volume-, and non-response to bronchodilation in patients with SAOP. An additional objective was to assess whether impulse oscillometry (IOS) parameters allow the diagnosis of SAOP and its reversibility.Methods:Fifty consecutive adult patients with SAOP (FEV1 and FVC < lower limit of normal, FEV1/FVC and TLC > lower limit of normal) diagnosed on spirometry and plethysmography underwent the assessment of reversibility (400 µg salbutamol) on FEV1, FVC, IC and IOS parameters.Results:The diseases most frequently associated with SAOP were COPD and asthma (26 and 15 patients, respectively). Six patients were flow-responders, 20 were volume-responders, 9 were flow and volume-responders and 15 patients were non-responders. Overall, 26 patients had a significant improvement of IC, and 35 / 50 (70%, 95%CI: 57-83) exhibited a significant bronchodilator response. The difference between Rrs5Hz and Rrs20Hz was increased in 28/50 patients (56%, 95%CI: 42-70 with value higher than upper limit of normal) and its decrease after bronchodilator significantly correlated to FEV1 increase only, suggesting proximal airway assessment.Conclusion:A significant reversibility, mainly assessed on IC increase, is frequent in Small Airways Obstructive Pattern. Impulse oscillometry is of limited value in this context because of its low sensitivity.

Highlights

Pellegrino et al in the interpretative strategies for lung function tests stated that special attention must be paid when FEV1 and FVC are concomitantly decreased and the FEV1/FVC ratio is normal or almost normal
Fifty consecutive adult patients with small airways obstructive pattern (SAOP) (FEV1 and FVC < lower limit of normal, FEV1/FVC and TLC > lower limit of normal) diagnosed on spirometry and plethysmography underwent the assessment of reversibility (400 μg salbutamol) on FEV1, FVC, IC and impulse oscillometry (IOS) parameters
The diseases most frequently associated with SAOP were COPD and asthma (26 and 15 patients, respectively)

Summary

Introduction

Pellegrino et al in the interpretative strategies for lung function tests stated that special attention must be paid when FEV1 and FVC are concomitantly decreased and the FEV1/FVC ratio is normal or almost normal. Apart incomplete inhalation or exhalation, these authors stated that a “possible cause of this pattern is patchy collapse of small airways early in exhalation” [1]. This small airways obstructive pattern (SAOP) is not infrequent, represents ~ 7% to 10% of all pulmonary function tests in two large databases and is not specific of any disease in adults [2, 3]. It can be encountered in asthmatic children [4]. A concomitant decrease in FEV1 and FVC with normal FEV1/FVC ratio and TLC defines small airways obstructive pattern (SAOP) and constitutes a classic pitfall of pulmonary-function-tests interpretation

Methods

Results

Conclusion