Avanzolini G, Barbini P, Bernardi F, Cevenini G, Gnudi G
Dipartimento di Elettronica, Informatica e Sistemistica, Università di Bologna, Italy.
Ann Biomed Eng. 2001;29(7):575-86. doi: 10.1114/1.1380418.
A physiologically based simulation model of breathing mechanics was considered in an attempt to interpret and explain the time course of input respiratory resistance during the breathing cycle, observed in recent studies on ventilated patients. The model assumes a flow-dependent Rohrer resistance for the upper extrathoracic airways and volume-dependent resistance and elastance for the intermediate airways. A volume-dependent resistance describes the dissipative pressure loss in the lower airways, and two constant elastances represent lung and chest wall elasticity. Simulated mouth flow and pressure signals obtained in a variety of well-controlled conditions were used to analyze total respiratory resistance and elastance estimated by an on-line algorithm based on a time-varying parameter model. These estimates were compared with those provided by classical estimation algorithms based on time-invariant models with two, three, and four parameters. The results show that the four-parameter model is difficult to identify, while the three-parameter one offers no substantial advantage for estimating input resistance with respect to the more simple two-parameter model. In contrast, the time-varying approach provides good on-line estimates of the simulated end-expiration and end-inspiration resistances. These values provide further information of potential clinical utility, with respect to time-invariant models. For example, the results show that the difference between the end-expiration and end-inspiration resistance increases when obstructions shift from the upper to the lower airways. The similarity of the results obtained with measured and simulated data indicates that, in spite of its simplicity, the simulation model describes important physiological mechanisms underlying changes in respiratory input resistance, specifically the mechanical properties of intermediate airways.
为了解释和说明在近期对通气患者的研究中观察到的呼吸周期中输入呼吸阻力的时间进程，我们考虑了一个基于生理的呼吸力学模拟模型。该模型假设上胸外气道存在流量依赖性罗勒阻力，中间气道存在容积依赖性阻力和弹性。容积依赖性阻力描述了下气道中的耗散压力损失，两个恒定弹性代表肺和胸壁弹性。在各种控制良好的条件下获得的模拟口腔流量和压力信号，用于分析基于时变参数模型的在线算法估计的总呼吸阻力和弹性。将这些估计值与基于具有两个、三个和四个参数的时不变模型的经典估计算法提供的估计值进行比较。结果表明，四参数模型难以识别，而三参数模型在估计输入阻力方面相对于更简单的两参数模型没有实质性优势。相比之下，时变方法能够很好地在线估计模拟的呼气末和吸气末阻力。相对于时不变模型，这些值提供了具有潜在临床应用价值的更多信息。例如，结果表明，当阻塞从上气道转移到下气道时，呼气末和吸气末阻力之间的差异会增加。实测数据和模拟数据获得的结果相似，这表明尽管该模拟模型简单，但它描述了呼吸输入阻力变化背后的重要生理机制，特别是中间气道的力学特性。
