where CL and Ccw are the compliances of the lung parenchyma and chest wall, respectively, and V_ ðt; 0Þ is the flow through the single generation-zero airway. Pressures and flows for connected airways in the network are related in the intuitive way: pressures are equal and volumes must sum at bifurcations, and the pressure drop down a segment is equal to the product of resistance and flow. Then from the resulting volume and pressure for each segment, resulting airway calibre is calculated using