Dynamic hyperinflation: an important target for treatment in asthma

Introduction: Dynamic hyperinflation (DH) results from small airway dysfunction and contributes to dyspnea in chronic obstructive airways disease (COPD). Whether DH is important in asthma is unknown. Aim: To investigate the prevalence of DH in asthma and its relationship with asthma symptoms. Method: Non-smoking (≤10 packyears), non-obese (BMI 25 kg/m 2 ) adults with asthma and FEV1/FVC ≤80% predicted despite GINA step 4-5 treatment completed questionnaires (SGRQ, CCQ, ACQ), performed lung function tests, and underwent a metronome-paced tachypnea (MPT) test to assess DH [1]. DH was defined as an MPT-induced reduction in inspiratory capacity (IC) ≥10%. Results: 27/31 patients (52% male, mean age 62 yr, mean FEV1 71% predicted) showed DH. Higher reductions in IC were related to poorer scores on ACQ (r=0.54, p=0.002), CCQ (r=0.52, p=0.003) and SGRQ (r=0.40, p=0.03), higher fluticasone dose (r=0.37, p=0.04), and to more bronchodilator reversibility (r=0.36, p=0.05) but not to FEV1. Patients with blood eosinophils ≥0.3x10E 9 /L showed stronger relationships between DH and poor symptom scores (ACQ r=0.82, p=0.002; CCQ r=0.70, p=0.02; SGRQ r=0.76, p=0.006). Conclusion: Dynamic hyperinflation is common in asthma and is strongly related to symptom scores, in particularly in patients with high blood eosinophils. This suggests that in these patients dynamic hyperinflation resulting from small airway inflammation is an important target for treatment. Reference: 1. Lahaije AJMC, Willems LM, van Hees HWH, et al. Diagnostic accuracy of metronome-paced tachypnea to detect dynamic hyperinflation. Clin Physiol Funct Imaging. 2013;33(1):62-9.