Regulating the larynx by expiratory pressure load training to improve aerobic capacity in advanced COPD: a substudy of the randomised, controlled EPT trial

<bold>Rationale:</bold> Improvements of exercise tolerance remain inadequate in advanced chronic obstructive pulmonary disease (COPD). The hypothesis that laryngeal narrowing in COPD is a potential treatment target of expiratory pressure load training (EPT) to improve exercise tolerance by obtaining adequate expiration was tested in the EPT study, in which the effect of 3-month EPT was assessed in 47 COPD across all GOLD grades, randomly allocating 1:1 to EPT or control groups. <bold>Methods:</bold> The aim of this substudy was investigate the effect of EPT with a focus on peak oxygen uptake (<italic>V′</italic>_O2) in GOLD III-IV cases. <bold>Results:</bold> Compared with controls (n=10), EPT increased (n=10): 1) peak <italic>V′</italic>_O2 with estimated treatment effect (ETE): +2.1 mL×min⁻¹×kg⁻¹, p=0.0004; 2) glottic dilatation ratio (GDR) at maximum collapse on laryngoscopy in the submaximal exercise with ETE: +28%, p=0.0001; and 3) mean expiratory flow (<italic>V</italic>_Tex/T_E) at peak exercise with ETE: +91 mL× sec⁻¹ p=0.0073, improving the St George’s Respiratory Questionnaire (SGRQ) total with an ETE of -9.7, p=0.0088. Across GOLD III-IV grades, the responses of <italic>V</italic>_Tex/T_E and GDR at maximum collapse were selected as more influential variables correlating with the improvement in peak <italic>V′</italic>_O2. <bold>Conclusion:</bold> EPT improved aerobic capacity and health status with higher <italic>V</italic>_Tex/T_E and larger laryngeal widening in advanced COPD.