Influence of inspiratory muscle weakness in exercise capacity of patients with chronic thromboembolic pulmonary hypertension (CTEPH)

Introduction: Despite therapeutic advances, exercise capacity of patients with CTEPH is often compromised. In addition to central haemodynamic impairment, systemic inflammation and low oxygen delivery may lead to abnormalities in peripheral striated muscles with important repercussion in muscular groups placed under high demand conditions. Since excessive ventilation is a key feature of patients with CTEPH, we hypothesize that inspiratory muscle weakness (IMW) is a frequent finding and may be associated with exercise impairment. Objective: To evaluate the frequency of IMW [maximal inspiratory pressure (Pi MAX ) pred ] in patients with CTEPH and its association with peak VO 2 obtained at cardiopulmonary exercise test (CPET) and distance of 6 minute walk test (6MWT). Methods: 24 patients with CTEPH [54±11 yrs; 38% male; 46% in NYHA functional class (FC) III/IV], confirmed by right-heart catheterization, underwent a CPET, 6MWT and PI MAX measurements. Results: Pi max pred was found in 41% of patients. Despite similar haemodynamics [cardiac index 2.4±0.6 vs 2.2±0.4L/min/m 2 and pulmonary vascular resistance (PVR) 854 ± 317 vs 823 ± 374 dynes.s.cm -3 ], patients with IMW showed lower 6MWD (342 ± 99 vs 442 ± 67m), lower peak VO 2 (50.8 ± 9.4 vs 63.8 ± 17.2% predicted) and increased ΔVE/ΔVCO 2 , compared to patients with Pi MAX >70% pred (p MAX was the only independent predictor of Peak VO 2 (partial r 0.445, p 0.04). Similar results were found for 6MWD as outcome variable. Conclusions: Pi MAX was independently associated with exercise capacity, when adjusted for resting heamodynamics and FC.