Fig 1. The measured airway pressure consists of 4 pressure components: 1) Pressure drop due to airway resistance (P_rs); 2) pressure in the lung compartments (Plung(t) = Elung(t) ×V(t)); 3) A constant chest wall pressure, P_chest = E_chest(t)×V(t); and 4) Demand pressure, P_demand = E_demand(t)×V(t).