Severe hyperkyphosis reduces the aerobic capacity and maximal exercise tolerance in patients with Scheuermann disease

Abstract

BACKGROUND CONTEXTThe evaluation of ventilatory functional restrictions during a maximal exercise tolerance test in patients with Scheuermann disease has never been described. PURPOSEThis study evaluated the respiratory functional capacity of patients with Scheuermann disease compared to healthy adolescents matched in age. STUDY DESIGN/SETTINGProspective comparative study. PATIENTS SAMPLEForty-one consecutive adolescents with Scheuermann hyperkyphosis (SK) and 20 healthy controls matched in age were included in the study. OUTCOME MEASURESBasal spirometry and dynamic ventilatory parameters were measured during a maximal cardiopulmonary exercise tolerance test. Heart rate, oxygen saturation (SatO2), maximum oxygen uptake (VO2 max), quotient between ventilation and volume of exhaled carbon dioxide (VE/CO2), respiratory exchange rate (RER), ventilatory capacity at maximal exercise (VEmax), and test duration were recorded at initium and at maximal exercise. METHODSThe exercise tolerance test (ETT) was completed to exhaustion using a standard Bruce protocol on a ramp treadmill. Comparisons of quantitative variables between SK and control group were analyzed by statistical nonparametric test. The correlations between the magnitude of the thoracic kyphosis and both the VO2 max/kg and VEmax of the SK group were also analyzed. No funds were required. The authors have no conflicts of interests. RESULTSPatients with SK started the test with a higher heart rate (p<.01) and reached exhaustion with a lower heart rate (p<.05) than healthy controls. At maximal exercise, the SatO2 was declined in Scheuermann patients compared to healthy subjects (p<.05). The maximal aerobic power (VO2max) was greater in healthy controls than in hyperkyphotic patients (50.0±6.7 vs. 43.4±11.3 mL/kg/min; p<.05). There was an inverse correlation between the increase in the magnitude of thoracic kyphosis and the deterioration of the maximal aerobic power. VO2max and VEmax were severely deteriorated in patients with more than 75° kyphosis. Patients with >75° thoracic kyphosis also showed an impairment in their cardiovascular efficiency as measured by the heart rate/VO2 quotient. The limited tolerance to the exercise in SK patients was reflected by a shorter duration of the exercise test and a lower energy cost measured in METS (metabolic equivalents) as compared to healthy controls. CONCLUSIONSPatients with severe hyperkyphosis (>75°) show significant respiratory inefficiency together with a lower ventilation capacity and lower VO2max. There is an inverse correlation between the increase in the magnitude of thoracic kyphosis and the deterioration of the maximal aerobic power.