FRACTAL NATURE OF SHORT-TERM SYSTOLIC BP AND HR VARIABILITY DURING LOWER-BODY NEGATIVE-PRESSURE
FRACTAL NATURE OF SHORT-TERM SYSTOLIC BP AND HR VARIABILITY DURING LOWER-BODY NEGATIVE-PRESSURE
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DOI：
10.1152/ajpregu.1994.267.1.r26
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发表时间：
1994-07-01
影响因子：
--
通讯作者：
HUGHSON, RL
中科院分区：
文献类型：
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作者：
BUTLER, GC;YAMAMOTO, Y;HUGHSON, RL
我们之前已经证明，心率变异性 (HRV) 信号本质上是分形，具有高度复杂性，如计算的分形维数 (D-F) 所示。我们还报道，复杂性的损失（如 HRV D-F 的降低所示）与直立性低血压和即将发生的晕厥相关。为了扩展心血管反应的研究，我们研究了与直立应激期间 HRV 测量一致的短期收缩压变异性 (BPV) 的信号特征。八名健康男性完成了 20 分钟仰卧休息的测试方案，随后在 -5、-15、-25、-40 和 -50 毫米汞柱下体负压 (LBNP) 下各休息 10 分钟，然后仰卧恢复 10 分钟。我们发现静息 BPV 和 HRV 是分形的，这两个变量在变异性信号的分形分量中的比例与 70% 相似。 HRV 的 1/f(beta) 关系斜率为 1.16 +/- 0.12，BPV 的 1/f(beta) 关系斜率为 2.31 +/- 0.17。随着立位应力水平的增加，HRV 的 1/f(β) 斜率在 -50 mmHg LBNP 下显着增加至 1.68 +/- 0.08，而 BPV 的 1/f(β) 斜率没有变化。源自心率变异性的副交感神经系统活动指标和交感神经系统活动指标表明，随着 LBNP 的增加，其值分别降低和增加。这些数据表明直立应激下心率和血压控制存在重要差异。
We have shown previously that the heart rate variabil ity (HRV) signal is fractal in nature with a high degree of complexity, as given by the calculated fractal dimension (D-F) We have also reported that loss of complexity, as indicated by a reduction in D-F of HRV, is associated with orthostatic hypotension and impending syncope. To extend this investigation of cardiovascular responses, we have investigated the signal characteristics of short-term systolic blood pressure variability (BPV) coincident with measurements of HRV during orthostatic stress. Eight healthy men completed a test protocol of 20 min supine rest followed sequentially by 10 min at each of -5, -15, -25, -40, and -50 mmHg lower body negative pressure (LBNP) and 10 min supine recovery. We found that resting BPV and HRV were fractal with similar to 70% of both variables in the fractal component of the variability signal. The slope of the 1/f(beta) relationship was 1.16 +/- 0.12 for HRV and 2.31 +/- 0.17 for BPV. With increasing levels of orthostatic stress, the 1/f(beta) slope of HRV increased significantly to 1.68 +/- 0.08 at -50 mmHg LBNP, whereas the 1/f(beta) slope was unchanged for BPV. Indicators of parasympathetic and sympathetic nervous system activity derived from heart rate variability suggested reduced and increased values, respectively, as the LBNP increased. These data indicate important differences in heart rate and blood pressure control under orthostatic stress.