Khoo M C
Biomedical Engineering Department, University of Southern California, Los Angeles, CA 90089, USA.
Respir Physiol. 2000 Sep;122(2-3):167-82. doi: 10.1016/s0034-5687(00)00157-2.
This paper reviews the major mechanisms that can give rise to various forms of variability in the ventilatory pattern. First, an elevated controller gain, coupled with the presence of delays and response lags in the chemoreflex loops, can lead to instability in feedback control and give rise to periodic breathing. This form of ventilatory stability can be assessed quantitatively by employing the concept of 'loop gain'. Several different methods of estimating loop gain from steady state or dynamic respiratory measurements are discussed. An inherently stable respiratory control system can also exhibit periodic behavior due to the influence of primary fluctuations in sleep-wake state and other physiological variables, such as cardiac output and cerebral blood flow. Self-sustained, irregular ventilatory fluctuations may be generated by nonlinear dynamic interactions between various components of the respiratory control system, such as the lung vagal afferents and the respiratory pattern generator, or through the propagation of stochastic disturbances around the chemoreflex loops.
本文综述了可导致通气模式出现各种形式变异性的主要机制。首先，升高的控制器增益，再加上化学反射回路中存在延迟和反应滞后，可导致反馈控制不稳定并引发周期性呼吸。这种通气稳定性形式可通过采用“回路增益”的概念进行定量评估。文中讨论了几种从稳态或动态呼吸测量中估计回路增益的不同方法。由于睡眠-觉醒状态以及心输出量和脑血流量等其他生理变量的原发性波动的影响，本质上稳定的呼吸控制系统也可能表现出周期性行为。呼吸控制系统的各个组成部分之间的非线性动态相互作用，如肺迷走神经传入纤维和呼吸模式发生器之间的相互作用，或通过化学反射回路周围随机干扰的传播，可能产生自持性、不规则的通气波动。
