Diaphragm function in patients with asthma and healthy controls: A cross-sectional study

Asthma is a chronic respiratory disease characterized by airway inflammation and variable respiratory symptoms. While peripheral muscle deconditioning is known to affect lung function and exercise tolerance, the role of respiratory muscle dysfunction, particularly the diaphragm, remains underexplored.

We aim to evaluate potential differences in diaphragm function in patients with asthma.

We conducted a prospective, observational study comparing diaphragmatic function of 50 patients with asthma and 50 healthy controls. Two independent operators evaluated diaphragm contraction using tidal breathing thickening fraction (TF). Diaphragm dysfunction was defined as a TF < 20 %. Additional assessments included flow-volume spirometry, impulse oscillometry (IOS), FeNO, blood eosinophil count, and the Sniff Inspiratory Nasal Pressure (SNIP) test.

Patients with asthma demonstrated significantly reduced diaphragm TF compared to healthy controls (p < 0.0001). Diaphragm dysfunction was significantly more prevalent in asthmatic patients (p < 0.0001), affecting 62%-66 % of the right hemidiaphragm and 46%-54 % of the left. Reduced TF was associated with longer disease duration (p = 0.03) and higher exacerbation rates (p = 0.04). No significant correlations were observed between TF and anthropometric data, asthma treatments, lung function, or Th2 biomarkers. SNIP measurements did not correlate with diaphragm TF. The limited sample size and the cross-sectional design were the main limitations of the study.

Diaphragm dysfunction is prevalent in asthma and associated with disease severity, including exacerbation frequency and longer disease duration. Impaired diaphragm function may contribute to persistent symptoms and exercise intolerance, representing a novel treatable trait in asthma management.