Author + information
To investigate the degree of decline in exercise capacity and ventilatory efficiency in patients with severe pulmonary hypertension (PH) and to aid in developing more effective rehabilitation programs.
This study was carried out in a cross-sectional observational way. From August 1st, 2014 to March 31st, 2016, this study recruited 15 patients with severe PH as the PH group, including 7 patients with idiopathic pulmonary arterial hypertension(IPAH), 6 PH patients associated with congenital heart disease (PH-CHD), 1 patients with chronic thromboembolic pulmonary hypertension(CTEPH) and 1 PH patients associated with rheumatic disease (PH-RHD). After consent and clearance of contraindications, PH group underwent right-heart catheterization, pulmonary function test (PFT) and performed the 6-min walk test and symptom-limited cardiopulmonary exercise testing (symptom-limited CPET). Twenty-three healthy subjects, matched by age, sex, and body size were used as controls, also had CPET and PFT measurements. Variables, including peak oxygen uptake per kilogram (peak VO2/kg), oxygen uptake efficiency slope (OUES) and percentages of their predicted values (peak VO2/kg of pred%,OUES%), end-tidal carbon dioxide partial pressure at anaerobic threshold (PETCO2@AT), lowest ventilation to carbon dioxide ratio (lowest VE/VCO2) were obtained. All data were computed with SPSS windows 13.0. Differences between two groups were compared using two independent samples t-test, with p less than 0.05 considered significant.
No adverse events occurred during this study. Only one PH patient failed to reach anaerobic threshold. Exercise capacity, as measured by peak VO2/kg and peak VO2/kg of pred% (16.12±2.96 ml·kg-1·min-1 vs 29.03±6.26 ml·kg-1·min-1; 44.2±13.3% vs 87.1±21.1%, respectively, both p < 0.001) was markedly lower in PH group. Additionally, PH group had lower OUES, OUES%, PETCO2@AT and higher lowest VE/VCO2 (901.6±306.6 ml/min/L/min vs 2085.0±454.4 ml/min/L/min; 40.7±16.5% vs 95.3±22.4%; 26.5±4.2 mmHg vs 41.5±3.2 mmHg; 45.20±9.78 vs 27.15±3.31,respectively, all p < 0.001). No significant difference was found in breath reserve (BR%,42.1±13.1% vs 44.3±11.3%, p = 0.592).
This study suggests that exercise capacity of patients with severe PH is severely impaired, and they have a high V/Q mismatch response during exercise which indicates their reduced ventilatory efficiency. Furthermore, from this study we learn that CPET as a common exercise function assessment tool, can offer a comprehensive evaluation for PH patients and may help us establish scientific rehabilitation programs.
Key words: Pulmonary Hypertension; Exercise capacity; ventilatory efficiency; Cardiopulmonary Exercise Testing