Brunetto Antônio Fernando, Roseguini Bruno Tesini, Silva Bruno Moreira, Hirai Daniel Müller, Guedes Dartagnan Pinto
Departamento de Fisioterapia, Universidade Estadual de Londrina, PR.
Rev Assoc Med Bras (1992). 2005 Sep-Oct;51(5):256-60; discussion 255. doi: 10.1590/s0104-42302005000500015. Epub 2005 Oct 31.
Obesity is associated with alterations of the autonomic nervous system. Previous studies in adults have shown that obese individuals present a decreased cardiac autonomic response to postural challenges. However, little is known about the impact of overweight on autonomic responses to passive postural stress in adolescents.
to compare cardiac autonomic responses to the head-up tilt maneuver between obese and non-obese adolescents by analyzing heart rate variability.
Fourteen obese adolescents (15.5+/-1.6 years) were compared with twenty non-obese subjects (15.4+/-0.8 years). Cardiac autonomic modulation was studied by heart rate variability (HRV) analysis of 5 minute RR interval recordings before and after a 70 masculine head-up tilt maneuver. HRV was analyzed according to the time domain (TD) and frequency-domain (FD) methods. The power spectral components were studied at low (LF) and high (HF) frequencies and as the LF/HF ratio.
Obese adolescents demonstrated significantly lower HF normalized units (38.2+/-11.1 vs 53.9+/-15.5, p<0.05) and higher LF normalized units (60.7+/-11.3 vs 44.6+/-15.7, p<0.05) in the supine position. No difference was found in any HRV parameters after head-up tilt. When comparing differences between the orthostatic and supine positions, obese adolescents showed lesser changes of LF normalized units (22.4+/-12.6 vs 38+/-16.4, p<0.05) and HF normalized units (-21.9+/-12.4 vs -37.3+/-16.3, p<0.05).
Obese adolescents have an abnormal cardiac autonomic response to the head-up tilt maneuver, characterized principally by a decreased parasympathetic response.
肥胖与自主神经系统的改变有关。先前针对成年人的研究表明，肥胖个体对姿势变化的心脏自主神经反应降低。然而，关于超重对青少年被动姿势应激时自主神经反应的影响知之甚少。
通过分析心率变异性，比较肥胖和非肥胖青少年对抬头倾斜动作的心脏自主神经反应。
将14名肥胖青少年（15.5±1.6岁）与20名非肥胖青少年（15.4±0.8岁）进行比较。通过对70°男性抬头倾斜动作前后5分钟RR间期记录进行心率变异性（HRV）分析，研究心脏自主神经调节。根据时域（TD）和频域（FD）方法分析HRV。研究低频（LF）和高频（HF）频率下的功率谱成分以及LF/HF比值。
肥胖青少年在仰卧位时HF标准化单位显著更低（38.2±11.1对53.9±15.5，p<0.05），LF标准化单位更高（60.7±11.3对44.6±15.7，p<0.05）。抬头倾斜后，任何HRV参数均未发现差异。比较直立位和仰卧位之间的差异时，肥胖青少年的LF标准化单位变化较小（22.4±12.6对38±16.4，p<0.05），HF标准化单位变化也较小（-21.9±12.4对-37.3±16.3，p<0.05）。
肥胖青少年对抬头倾斜动作存在异常的心脏自主神经反应，主要表现为副交感神经反应降低。
