Neural drive and respiratory muscle effort in emphysema following lung volume reduction

Introduction Respiratory muscle impairment is common in patients with severe emphysema, primarily driven by lung hyperinflation. Endobronchial valve (EBV) treatment reduces hyperinflation and may restore respiratory mechanics in this patient population. Our aim was to investigate changes in neural drive and respiratory muscle recruitment following EBV treatment. Methods EBV-eligible emphysema patients from our prior study on diaphragm function were prospectively enrolled (NCT04735731). Respiratory muscle activation and timing were assessed using surface electromyography at baseline and 6 weeks following EBV treatment. Additionally, an age-matched control group without respiratory symptoms was included for comparison. Results We included 25 patients who underwent EBV treatment (mean FEV1 28% predicted, mean RV 233% predicted) and 12 controls. The inspiratory time (Ti) to total time of respiratory cycle (Ttot) ratio (0.35 vs 0.53; p=0.003) was significantly lower in patients compared to controls. Activity of the diaphragm (4.7 vs 0.9 µV; p<0.001) and intercostal muscles (1.2 vs 0.4 µV; p<0.001) during tidal breathing was significantly higher in patients. Furthermore, tonic (end-expiratory) activity of the diaphragm (1.4 vs 0.6 µV; p=0.012) and intercostal muscles (1.4 vs 0.6 µV; p=0.003) was significantly higher as well. Following EBV treatment, all measured outcomes improved significantly, approaching the values observed in the control group. Conclusion These findings indicate that neural drive and respiratory muscle effort are significantly elevated in severe emphysema patients. By reducing lung hyperinflation, endobronchial valve treatment reduces this load, resulting in improved respiratory mechanics and decreased work of breathing, an important contributor to dyspnoea severity.