Reduced dynamic hyperinflation after LVRS is associated with improved exercise tolerance

Introduction: Dynamic hyperinflation (DH) after lung volume reduction surgery (LVRS) has not been well studied. It is not known if reductions in DH correlate with improvements in exercise performance post-LVRS.

Methods: Forty-two upper-lobe predominant emphysema patients who underwent LVRS were analyzed. Inspiratory capacity was measured every 2 min during symptom-limited cardiopulmonary exercise test (CPET) and end-expiratory lung volumes (EELV) were calculated. The main measure of DH was EELV/TLC ratio matched at metabolic isotimes (based on the post-rehabilitation VCO2max).

Results: Patients had very severe airflow obstruction (FEV1 28.3 ± 7.0% predicted), were hyperinflated (TLC 125 ± 17% predicted) and gas trapped (RV 198 ± 39% predicted). Compared to the post-rehab baseline, dynamic hyperinflation (EELV/TLC) was significantly reduced after LVRS at 6, 12, 24, and 36 months. There were also increases in inspiratory reserve volume at matched isotimes after surgery. Patients adopted a slower, deeper breathing pattern during exercise after LVRS, which strongly correlated to reductions in DH. There were significant correlations between reductions in DH (EELV/TLC @50% VCO2max) and improvements in 6 min walk distance (Pearson r = -0.411, p = 0.02, n = 33) and maximal watts on CPET (Spearman r = -0.536, p = 0.001, n = 33) when comparing post-rehabilitation and 6 month post-LVRS values.

Conclusion: Dynamic hyperinflation during exercise was reduced after LVRS (up to 3 years) and there was a strong association between alterations in breathing pattern and reduced DH after LVRS. This is the first study to demonstrate that reductions in DH correlated with improved exercise performance following LVRS.