In this context, a previous study has shown that unloading the respiratory musculature with proportional assist ventilation (PAV) was associated with improved peripheral muscle oxygenation during constant-load exercise, as indicated by blunted changes in Δ deoxyhemoglobin ([deoxi-Hb + Mb]) determined by near-infrared spectroscopy (NIRS) and longer exercise tolerance in patients with HFrEF (Borghi-Silva et al., 2008a), chronic obstructive pulmonary disease (COPD) (Borghi-Silva et al., 2008b), and HFrEF-COPD coexistence (da Luz Goulart et al., 2020). The gene discussed is GSTM1; the disease is chronic obstructive pulmonary disease.