  In a recent paper we presented a simple two compartment model which describes
the influence of inhaled concentrations on exhaled breath concentrations for
volatile organic compounds (VOCs) with small Henry constants. In this paper we
extend this investigation concerning the influence of inhaled concentrations on
exhaled breath concentrations for VOCs with higher Henry constants.
  To this end we extend our model with an additional compartment which takes
into account the influence of the upper airways on exhaled breath VOC
concentrations.
