Effects of inspiratory muscle training in patients with chronic obstructive pulmonary disease after stratification by the degree of static hyperinflation

Abstract

<b>Background:</b> Inspiratory muscle training (IMT) is an intervention for patients with COPD, which can improve inspiratory muscle strength, exercise capacity and health status. While static hyperinflation is associated with altered respiratory mechanics, it is unclear whether patients with different baseline degrees of static hyperinflation respond differentially to IMT as part of pulmonary rehabilitation (PR). Therefore, the aim was to study the effects of IMT as an add-on on PR after stratification for baseline degrees of static hyperinflation. <b>Methods:</b> Retrospectively, data were extracted of 426 COPD patients (64% males, age: 68 (64-71) yrs, FEV1: 33 (26-46) pred.) referred for PR in Ciro, Horn, the Netherlands between June 2013 and October 2020. Patients were categorized in quintiles based on their residual volumes (RV). IMT was performed twice daily as part of a PR program. The primary outcome was maximal static inspiratory mouth pressure (MIP). Secondary outcomes were exercise capacity (constant-work rate test, CWRT and 6-min walk distance, 6MWD) and disease-specific health status (COPD Assessment Test). <b>Results:</b> In the whole sample MIP increased (10 (2-19) % pred.) (p&lt;0.001) with no significant differences between quintiles.&nbsp;Endurance time on the CWRT and health status improved significantly with no between-group differences.&nbsp;6MWD increased significantly but the change was higher in the lowest (+39 (9-92) m)&nbsp;vs. the baseline highest degree of static hyperinflation (+11 (-18-54) m) (p&lt;0.05). <b>Conclusion:</b> A decreased MIP in COPD patients improved following PR including IMT irrespective of the degree of static lung hyperinflation.