P.82 Case-Control cardiopulmonary exercise testing for patients with neuromuscular disease

Abstract

Patients with neuromuscular diseases (NMD) present with disease-specific muscle weakness and fatigue and are largely sedentary and deconditioned. This sedentary lifestyle leads to additional weakness, fatigue and loss of function. This deconditioning cycle results in reduced cardiorespiratory fitness (CRF), which is strongly related to increased risk for cardiovascular and pulmonary diseases (e.g. hypertension, diabetes mellitus, coronary artery disease, chronic obstructive pulmonary disease). These largely preventable diseases are the leading causes of morbidity and mortality for those with and without NMD. The gold standard for the assessment of CRF is peak oxygen consumption (peak VO2), assessed with cardiopulmonary exercise testing (CPX). Several small studies have suggested a role for CPX for patients with NMD, who present with hyperventilatory and hypercirculatory patterns, but with inconsistent results. We performed CPX in 37 patients with NMD and 8 controls using a Keiser wheelchair accessible total body trainer and a CosMed K5 wearable metabolic system. We were able to perform high quality CPX by both subjective and objective measures. Compared to controls, individuals with NMD presented with reduced exercise performance as measured by peak wattage and peak VO2. Disturbed hemodynamic and ventilatory patterns were noted, with borderline chronotropic incompetence and low O2 pulse, early and marked ventilatory inefficiency and severely reduced oxygen uptake efficiency slope and a high proportion of patients displaying exercise oscillatory breathing. Importantly, we observed that relative effort as illustrated by equivalent RPE and RER was not significantly different than controls. Our data illustrate that high quality CPX can be conducted in this population and suggest that performing CPX in patients with NMD will reveal distinct physiological profiles that may lead to a better understanding of cardiopulmonary and metabolic pathology in these individuals.