Effect of exercise training on respiratory muscle oxygenation in children with congenital heart disease

BACKGROUND: Diminished aerobic capacity and weakness of both respiratory and peripheral muscles have been observed in cardiac patients and may contribute to exercise limitation. The aim of this study was to evaluate the effects of a home-based training programme on aerobic fitness and oxygenation of the respiratory muscles in children with congenital heart disease (CHD). METHODS AND RESULTS: Eighteen patients with CHD aged 12-15 years participated in this study. Ten patients (training group, TG) underwent a training programme for 12 weeks and eight patients served as a non-training control group (CG). All subjects performed a cardiopulmonary exercise test before and after the study period. Oxygenation of the respiratory muscles was assessed using near-infrared spectroscopy. No significant differences were observed, at baseline and after the completion of the study, between the CG and TG in peak exercise workload, oxygen uptake (VO2), carbon dioxide output (VCO2), pulmonary ventilation (VE), and heart rate (HR). However, a significant improvement in exercise performance was found in the TG versus the CG when results were compared at the ventilatory threshold (Vth): workload (45.2+/-8.0 versus 58.5+/-7.4%; P<0.05), VO2 (62.3+/-7.5 versus 69.8+/-5.1%; P<0.05), VCO2 (49.8+/-5.7 versus 60.0+/-5.8%; P<0.05), VE (42.8+/-9.9 versus 50.1+/-9.5%; P<0.05), and HR (69.5+/-6.1 versus 76.0+/-3.5%; P<0.05). After training, an improvement in oxygenation of the respiratory muscles was found in the TG from 60% of VO2max until the end of exercise. At the Vth, the TG showed greater oxygenation after training (55.1+/-6.6 versus 43.0+/-6.9%, P<0.01, respectively). Furthermore, we showed a significant correlation of the change in respiratory muscle oxygenation and VO2 in the TG (r=0.90, P<0.01). CONCLUSION: It is concluded that general physical training at submaximal intensity induces better aerobic fitness and improves respiratory muscle oxygenation in children with CHD.