whereVD,N is the normalized dead space volume (VDV−1
D,o),VD,o is the
maximum dead space volume and Kp and n fitting parameters that
define the stiffness of the trachea. In adapting this equation from
Aljuri et al. (1999)we have assumed that the trachea does not compress
longitudinally, and therefore, tracheal volume is proportional
to cross-sectional area.