A reappraisal of inspiratory capacity in chronic obstructive pulmonary disease: clinical correlates and role of long-acting muscarinic antagonists and long-acting β2 agonists

ABSTRACT

Introduction

In patients with chronic obstructive pulmonary disease (COPD), static and dynamic hyperinflation, together with expiratory flow limitation and gas exchange abnormalities, is one of the major causes of dyspnea, decreased exercise performance and ventilatory failure. An increase in functional residual capacity (FRC) is accompanied by a decrease in inspiratory capacity (IC), which is a volume readily available, repeatable, and simple to measure with any spirometer. Changes in IC and FRC after bronchodilation, contrary to changes in FEV₁, have been closely associated with improvements in dyspnea and exercise performance. We systematically searched PubMed and Embase databases for clinical trials that assessed the effects of dual bronchodilation on inspiratory capacity in patients with COPD.

Areas covered

Despite their pivotal role in COPD, IC and static volumes have rarely been considered as primary outcomes in randomized clinical trials assessing the efficacy of bronchodilators. Available studies on dual bronchodilation have shown a significant and persistent positive impact on IC focusing mainly on patients with moderate-to-severe COPD, whereas dynamic hyperinflation is also present at milder disease stages.

Expert opinion

This narrative review discusses the pathophysiological and clinical importance of measuring IC in patients with COPD and how IC can be modified by maximizing bronchodilation combining long-acting muscarinic antagonists and long-acting β2 agonists.

KEYWORDS:

• Lung volume
• bronchodilation
• inspiratory capacity
• dyspnea
• dual bronchodilation
• hyperinflation

Article highlights

• COPD is characterized by tidal expiratory flow limitation, reduced elastic recoil, and only partially reversible airflow obstruction, which lead to progressive development of hyperinflation at rest, a phenomenon exacerbated by exercise.

• The increase in FRC and the decrease in IC in patients with COPD due to dynamic hyperinflation hinders the respiratory mechanics in case of hightened ventilatory demand such as during physical activity, resulting in fatigue and severe exertional dyspnea.

• Changes in IC and FRC after bronchodilation, contrary to changes in FEV1, have been found to be closely associated with improvements in dyspnea and exercise performance.

• IC can be significantly improved by maximizing bronchodilation with combinations of long-acting muscarinic antagonists (LAMA) and long-acting β2-agonists (LABA).

Declaration of Interest

D Radovanovic has received fees for participation on advisory boards and consultancy from AstraZeneca, Boehringer Ingelheim, Fondazione Internazionale Menarini, and GlaxoSmithKline, and fees for lecturing from AstraZeneca, Boehringer Ingelheim, Fondazione Internazionale Menarini. P Santus has received grants from Air Liquide, Boehringer Ingelheim, Chiesi Farmaceutici, Pfizer, and fees for lecturing and consultancy from AstraZeneca, Berlin-Chemie, Boehringer Ingelheim, Guidotti. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

Astra Zeneca unconditionally provided funds to sustain the linguistic review of the manuscript that was performed by Edra S.p.a. No specific grants or funds were provided at any time and by any entity to fund the writing of the manuscript.