MODELING INSPIRATION AND EXPIRATION MECHANISM OF LUNGS USING BOND GRAPH

Abstract

In modern technological era research in Mechanical Ventilators (MV) has drastically increased in designing model based MV treatment. In model based MV treatment mathematical model of lung is used to detect lungs diseases and determine the optimal MV settings to aid clinician. In proposed work, inspiration and expiration mechanism of lungs has been modelled using Bond Graphs. Bond graph modeling has preference over conventional modeling in such a way that differential equation do not complicate the system. Physical system is directly accessed and engineering model is developed after that it is converted to bond graph. Lung segments are assigned Hydraulic analogies using cylinders and accumulators. 65536 branches are modelled as 65536 cylinders with decreasing sizes. Upper airway from nostrils to trachea is modelled as single cylinder having resistance and associated compliance effect. Trachea to lower lung segment consists of 23 generations of airways. In this study, 4 generations are considered with their respective resistance and compliance, whereas resistance and compliance effect, of 5th to 17th generations are lumped. These are modelled with cylinders of decreasing size. Generation 17 to 23 are considered as respiratory zone that are modelled as accumulator having compliance and resistance associated. Grey-Box model estimation is used to estimate model parameters of 4 generations and controller is designed. 20 sim software is used to determine the relationship between Pressure (P) and Volume (V) and evaluate the model performance. Model is capable of predicting the true PV curves and thus leading to screening of lungs diseases. Model can be used for clinical trials with any existing MV.