Yamamoto W S
J Appl Physiol Respir Environ Exerc Physiol. 1981 Apr;50(4):835-43. doi: 10.1152/jappl.1981.50.4.835.
A simulation of ventilatory responses to infused and inhaled CO2 at controlled cardiac output and high and low levels of neural excitation mimics comparable experiments in animals. The model suggests that at low levels of endogenous and exogenous CO2 load the alert quiescent animal will show hyperpnea to both test states associated with hypercapnia. The nonalert quiescent animal simulated will show an isocapnic response to endogenous load and hypercapnic response to exogenous load. The explanation of this behavior lies in the model formulation, which allows the neural signal from metabolically active sources to drive the proportional component of the controller below an operating level established by its set point. By this reasoning the excited but metabolically inactive animal should be paradoxically less sensitive to small changes in CO2, whether exogenous or endogenous, than the quiescent animal. The model demonstrates further that a neural "exercise" signal in proportion to venous return better simulates observations in which CO2 load and venous return are dissociated than one in which the neural signal is computed from metabolism. The use of delta V/delta P slopes as estimates of sensitivity go awry in experiment and simulation when blood flow, CO2 level, and neural excitatory state are dissociated. This is particularly true when the organism is operating at and below the hypothesized set point.
在控制心输出量以及高低水平神经兴奋的条件下，对输注和吸入二氧化碳的通气反应进行模拟，类似于在动物身上进行的类似实验。该模型表明，在内源性和外源性二氧化碳负荷较低时，警觉安静的动物对与高碳酸血症相关的两种测试状态都会表现出呼吸增强。模拟的非警觉安静动物对内源性负荷表现出等碳酸反应，对外源性负荷表现出高碳酸反应。这种行为的解释在于模型公式，它允许来自代谢活跃源的神经信号驱动控制器的比例部分低于其设定点所确定的操作水平。据此推理，兴奋但代谢不活跃的动物，无论外源性还是内源性二氧化碳的小变化，应该比安静的动物反常地更不敏感。该模型进一步表明，与根据代谢计算神经信号相比，与静脉回流成比例的神经“运动”信号能更好地模拟二氧化碳负荷和静脉回流分离时的观察结果。当血流、二氧化碳水平和神经兴奋状态分离时，在实验和模拟中使用ΔV/ΔP斜率作为敏感性估计会出现偏差。当生物体在假设的设定点及以下运行时，情况尤其如此。
