Fortrat J O, Yamamoto Y, Hughson R L
Department of Kinesiology, University of Waterloo, Ontario, Canada.
Biol Cybern. 1997 Jul;77(1):1-10. doi: 10.1007/s004220050361.
The goal of our study was to determine whether evidence for chaos in heart rate variability (HRV) can be observed when the respiratory input to the autonomic controller of heart rate is forced by the deterministic pattern associated with periodic breathing. We simultaneously recorded, in supine healthy volunteers, RR intervals and breathing volumes for 20 to 30 min (1024 data point series) during three protocols: rest (control), fixed breathing (15 breath/min) and voluntary periodic breathing (3 breaths with 2 s inspiration and 2 s expiration followed by an 8 s breath hold). On both the RR interval and breathing volume series we applied the non-linear prediction method (Sugihara and May algorithm) to the original time series and to distribution-conserved isospectral surrogate data. Our results showed that, in contrast to the control test, during both fixed and voluntary periodic breathing the variability of breathing volumes was clearly deterministic non-chaotic. During all the three protocols, the RR-interval series' non-linear predictability was consistent with one of a chaotic series. However, at rest, no clear difference was observed between the RR-interval series and their surrogates, which means that no clear chaos was observed. During fixed breathing a difference appeared, and this difference seemed clearer during voluntary periodic breathing. We concluded that HRV dynamics were chaotic when respiration was forced with a deterministic non-chaotic pattern and that normal spontaneous respiratory influences might mask the normally chaotic pattern in HRV.
我们研究的目的是确定当心率自主控制的呼吸输入受到与周期性呼吸相关的确定性模式的驱动时，是否能观察到心率变异性（HRV）中混沌的证据。我们在仰卧位健康志愿者中，于三种方案期间同时记录RR间期和呼吸量20至30分钟（1024个数据点序列）：静息（对照）、固定呼吸（15次/分钟）和自主周期性呼吸（吸气2秒、呼气2秒，随后屏气8秒，共3次呼吸）。在RR间期和呼吸量序列上，我们对原始时间序列和分布守恒的等谱替代数据应用了非线性预测方法（杉原和梅算法）。我们的结果表明，与对照测试相比，在固定呼吸和自主周期性呼吸期间，呼吸量的变异性明显是确定性的而非混沌的。在所有三种方案中，RR间期序列的非线性可预测性与混沌序列之一一致。然而，在静息时，RR间期序列与其替代数据之间未观察到明显差异，这意味着未观察到明显的混沌。在固定呼吸期间出现了差异，而在自主周期性呼吸期间这种差异似乎更明显。我们得出结论，当呼吸受到确定性非混沌模式的驱动时，HRV动态是混沌的，并且正常的自发呼吸影响可能掩盖了HRV中通常的混沌模式。
