Background: Patients with congenital scoliosis often have restrictive pulmonary dysfunction on static pulmonary function testing (PFT). Although frequently asymptomatic during daily activities, these patients are generally assumed to have reduced exercise capacity. The aim of this study was to use dynamic cardiopulmonary exercise testing (CPET) to investigate exercise capacity and its association with spinal deformity in patients with congenital scoliosis.
Methods: Sixty patients with congenital scoliosis who underwent preoperative spinal radiography, PFT, and CPET were included from January 2014 to November 2017. The impact of thoracic spinal deformity and rib anomalies on pulmonary function and physical capacity was investigated.
Results: A significant deterioration in pulmonary function with increases in the severity of the major thoracic curve was demonstrated by the forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and total lung capacity (all p < 0.001). The ratio of FEV1 to FVC was similar regardless of thoracic curve severity. A smaller tidal volume during exercise testing reflected restrictive dysfunction in the patients with the most severe curves. CPET also revealed a significant trend of faster breathing by patients with a severe thoracic curve (p < 0.001). Exercise capacity indicators such as work rate (p = 0.019), heart rate (p = 0.015), and oxygen saturation (p = 0.006) were significantly reduced only in patients with a thoracic curve of >100°. Pulmonary dysfunction was the major contributor to exercise intolerance. Compared with mild pulmonary dysfunction, moderate and severe dysfunction was associated with an abnormal breathing pattern and lower work rate (p = 0.032) and peak oxygen intake (p = 0.042), indicating worse exercise tolerance.
Conclusions: Congenital scoliosis leads to restrictive pulmonary dysfunction, which reduces the tidal volume and forces patients to accelerate respiratory rates during exercise. Patients with a thoracic curve of >100° are unable to compensate and have significantly reduced exercise capacity.
Level of evidence: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.