Cushway James, Murphy Liam, Chase J Geoffrey, Shaw Geoffrey M, Desaive Thomas
University of Canterbury, Department of Mechanical Engineering, Christchurch, New Zealand.
University of Canterbury, Department of Mechanical Engineering, Christchurch, New Zealand.
Comput Methods Programs Biomed. 2022 Jun;220:106819. doi: 10.1016/j.cmpb.2022.106819. Epub 2022 Apr 17.
Mechanical ventilation causes adverse effects on the cardiovascular system. However, the exact nature of the effects on haemodynamic parameters is not fully understood. A recently developed cardio-vascular system model which incorporates cardio-pulmonary interactions is compared to the original 3-chamber cardiovascular model to investigate the exact effects of mechanical ventilation on haemodynamic parameters and to assess the trade-off of model complexity and model reliability between the 2 models.
Both the cardio-pulmonary and three chamber models are used to identify cardiovascular system parameters from aortic pressure, left ventricular volume, airway flow and airway pressure measurements from 4 pigs during a preload reduction manoeuvre. Outputs and parameter estimations from both models are contrasted to assess the relative performance of each model and to further investigate the effects of mechanical ventilation on haemodynamic parameters.
Both models tracked measurements accurately as expected. There was no identifiable increase in error from the added complexity of the cardio-pulmonary model, with both models having a mean average error below 0.5% for all pigs. Identified left ventricle and vena cava elastances of the 3-chamber model was found to diverge exponentially with PEEP from identified left ventricle and vena cava elastances of the cardio-pulmonary model. The r of the fit for each pig ranged from 0.888 to 0.998 for left ventricle elastance divergence and from 0.905 to 0.999 for vena cava elastance divergence. All other identified parameters showed no significant difference between models.
Despite the increase in model complexity, there was no loss in the cardio-pulmonary model's ability to accurately estimate haemodynamic parameters and reproduce system dynamics. Furthermore, the cardio-pulmonary model was able to demonstrate how mechanical ventilation affected parameter estimations as PEEP was increased. The 3-chamber model was shown to produce parameter estimations which diverged exponentially with PEEP, while the cardiopulmonary model estimations remained more stable, suggesting its ability to produce more physiologically accurate parameter estimations under higher PEEP conditions.
机械通气会对心血管系统产生不良影响。然而，其对血流动力学参数影响的确切性质尚未完全明确。将最近开发的纳入心肺相互作用的心血管系统模型与原始的三室心血管模型进行比较，以研究机械通气对血流动力学参数的确切影响，并评估这两种模型在模型复杂性和模型可靠性之间的权衡。
使用心肺模型和三室模型，根据4头猪在预负荷降低操作期间的主动脉压力、左心室容积、气道流量和气道压力测量值来识别心血管系统参数。对比两种模型的输出和参数估计值，以评估每个模型的相对性能，并进一步研究机械通气对血流动力学参数的影响。
两种模型均如预期那样准确跟踪测量值。心肺模型增加的复杂性并未导致可识别的误差增加，所有猪的两种模型平均误差均低于0.5%。发现三室模型识别出左心室和腔静脉弹性与心肺模型识别出的左心室和腔静脉弹性随呼气末正压（PEEP）呈指数级差异。每头猪左心室弹性差异的拟合r值范围为0.888至0.998，腔静脉弹性差异的拟合r值范围为0.905至0.999。其他所有识别出的参数在模型之间无显著差异。
尽管模型复杂性增加，但心肺模型准确估计血流动力学参数和再现系统动力学的能力并未丧失。此外，心肺模型能够证明随着PEEP增加，机械通气如何影响参数估计。三室模型显示产生的参数估计值随PEEP呈指数级差异，而心肺模型的估计值保持更稳定，表明其在更高PEEP条件下产生更符合生理实际的参数估计值的能力。
