Respiratory system model based on PSPICE

The aim of the present work is the building of a lumped nonlinear dynamic model of lung/airway mechanics using generic instead of specific software, in an attempt to offer an open simulation environment. Based on the analogy between pneumatic and electric magnitudes, an electrical equivalent circuit of the lung/airway mechanics is derived. Then, the nonlinear circuit elements are constructed by means of the powerful Analog Behavioral Modeling (ABM) building blocks and the system is solved using PSPICE. Following the approach in [3] and [4], five lumps are defined: two capacitors (elastances) corresponding to lung and collapsible airway segment and three resistors, corresponding to lung, collapsible airway segment and upper airway. The element definition involves as much as five parameters for the lung, four parameters for the collapsible segment and two parameters for the upper airway. The model does not attempt to mimic any particular system adjusting a given set of parameters but instead to provide a tool to explore the relationship between a given parameter or set of parameters and the system response. In particular, Forced Vital Capacity (FVC) maneuver and tidal breathing will be explored.