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

Abstract

Background context: The evaluation of ventilatory functional restrictions during a maximal exercise tolerance test in patients with Scheuermann disease has never been described.

Purpose: This study evaluated the respiratory functional capacity of patients with Scheuermann disease compared to healthy adolescents matched in age.

Study design/setting: Prospective comparative study.

Patients sample: Forty-one consecutive adolescents with Scheuermann hyperkyphosis (SK) and 20 healthy controls matched in age were included in the study.

Outcome measures: Basal 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.

Methods: The 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.

Results: Patients 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.

Conclusions: Patients 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.

Keywords: Cardiopulmonary exercise test; Hyperkyphosis; Maximal oxygen uptake; Respiratory function; Scheuermann disease; Ventilatory efficiency.