Comparing CPET and 6MWT for Assessing Exercise Capacity in Systemic Sclerosis Patients with Pulmonary Involvement

<bold>Introduction:</bold> Pulmonary involvement in Systemic Sclerosis (SSc) significantly contributes to disease-related morbidity and mortality. Impaired exercise capacity serves as a prognostic indicator for mortality in SSc. Assessments commonly used to evaluate physical fitness include the six-minute walk test (6MWT) and cardiopulmonary exercise testing (CPET). <bold>Objectives:</bold> To compare physical fitness and indirect markers of pulmonary circulation dysfunction in SSc patients with pulmonary involvement to healthy controls during maximal CPET and 6MWT a portable CPET unit. <bold>Results:</bold> During both tests, patients performed maximal effort (CPET RER=1.17 vs. 6MWT RER=1.08). SSc patients demonstrated impaired exercise tolerance: low peakVO2 values during both maximal CPET (mean peak VO2=1027 mL/min; 66% of predicted value) and 6MWT (mean peak VO2 937 mL/min; 64.5 % of predicted value), along with exercise-induced desaturation (−26% in CPET vs. -19% 6MWT) and decreasing PETCO2 values (mean CPET rest PETCO2= 31.5 mmHg, mean CPET max PETCO2=30 mmHg vs. mean 6MWT rest PETCO2=29 mmHg, mean 6MWT max PETCO2=31 mmHg). Only maximal CPET revealed abnormalities in ventilation-perfusion ratio, expressed as an elevated VE/VCO2 slope (mean CPET VE/VCO2 slope=43.2, vs. mean 6MWT VE/VCO2 slope=33.95), and ventilation abnormalities, manifested as reduced breathing reserve (mean CPET BR=12.6%, vs. mean 6MWT BR=63.4%). The research is currently ongoing. <bold>Conclusions:</bold> Maximal CPET on a cycle ergometer appears to be a superior tool for assessing exercise capacity and reasons for its limitation in individuals with SSc, aiding in disease progression monitoring and treatment compared to the 6MWT.