Dynamic Hyperinflation in Patients With Moderate-Severe Asthma: Relationship With Clinical Control and Small Airway Dysfunction

Abstract

Background: Dynamic hyperinflation (DH), characterized by an abnormal increase in operative lung volumes during exercise, is associated with breathlessness and exercise intolerance. This study aimed to evaluate the relationship between DH and control of symptoms in patients with moderate-severe asthma.

Methods: A cross-sectional, multicenter, observational study was conducted in patients with moderate-severe asthma. DH was defined as a decrease in inspiratory capacity after a 6-minute walk test (6MWT), and asthma control was measured using the Asthma Control Test (ACT) and Spanish Guidelines for the Management of Asthma (GEMA). Secondary variables included sensitization to aeroallergens (prick test), quality of life (miniAQLQ), anxiety or depression, dyspnea (mMRC), fatigue (Borg scale), and small airway dysfunction (oscillometry).

Results: Among the 154 patients analyzed, 97 (63%) had DH. ACT scores did not differ significantly between patients with and without DH (20.8 [4.4] vs 21.7 [3.6]; P=.411). However, the percentage of patients with partially and poorly controlled asthma according to GEMA was significantly higher in the DH group than in those without DH (40.2% vs 24.6%; P=.048). Compared with patients without DH, patients with DH had higher dyspnea scores (0.9 [0.9] vs 0.5 [0.6]; P=.009), greater fatigue before the 6MWT (1.3 [1.9] vs 0.5 [1.1]; P=.004), higher respiratory reactance (0.7 [1.2] vs 0.4 [1.2] cmH2O/L/s; P=.032), higher depression scores (4.2 [3.7] vs 2.1 [2.1], P=.002), and lower sensitization to aeroallergens (45.4% vs 68.4%; P=.014).

Conclusions: Although no relationship was found between DH and uncontrolled asthma via the ACT, the proportion of patients with uncontrolled asthma according to GEMA was significantly higher in the DH group.

Keywords: Asthma control; Dynamic hyperinflation; Dyspnea; Oscillometry; Prevalence.