Bronchodilator Response Assessment of the Small Airways Obstructive Pattern



Plamen Bokov1, 2, Clémence Martin1, Sémia Graba1, Karine Gillet-Juvin1, Mohamed Essalhi1, Christophe Delclaux1, 2, *
1 AP-HP ; Hôpital Européen Georges Pompidou ; Service de Physiologie, Paris. France
2 Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, Paris. France


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© 2017 Bokov et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Service de Physiologie Pédiatrique, Université Paris Diderot, Hôpital Robert Debré, 48, boulevard Sérurier, 75019 Paris, France; Tel: 33140034190; E-mail: christophe.delclaux@aphp.fr


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.

Keywords: Pulmonary function testing, Bronchodilator response, Impulse oscillometry, Obstructive defect, Inspiratory capacity, Distal airways.