Two different ways of expressing breathing, one as if using a ventilator at the mouth and the other one as human pleural muscle generating pressure gradient against external pressure. Three models used to compare differences.

Description

  These models compare three situations, each with two compartments having resistances, 
  compliances, switches and initial masses of specie in the two tanks. The first model 
  has a pressure source in external air as in the case of breathing support of patient 
  with a ventilator. The second model has a pressure source attached to the most inner 
  tank as in the case of regular human breathing, when the tension of pleural muscle 
  controls the generated pressure difference. Depending on the compliances and volumes 
  of the tanks, time elapsed to reach the stationary conditions may vary slightly. 
  However, the two cases show the same long time flow and concentration characteristics. 
  The last model shows the case when internal and external pressure sources are applied 
  simultaneously. It simulates the situation when a patient initially on a breathing 
  support starts to breath on his own, but the ventilator is still active.  	

Equations

The governing equations are

External Pressure Source at the mouth

**Pleural Muscle as a Pressure Source** 

The equations for this model may be viewed by running the JSim model applet and clicking on the Source tab at the bottom left of JSim's Run Time graphical user interface. The equations are written in JSim's Mathematical Modeling Language (MML). See the Introduction to MML and the MML Reference Manual. Additional documentation for MML can be found by using the search option at the Physiome home page.