Let us consider the two following equations that describe the
nonlinear Ptn-V̇ relationship:
where K_{1} is a constant that accounts for
the linear flow dependence of Ptn and
K_{2} is a constant that accounts for its nonlinear
flow dependence. Because NR is calculated at the 0.5 L/s flow, NR
derived from equation 1 is given by
and NR derived from equation 2 is given by
In our previous study,^{7} we showed that the relative
contributions of the K_{1} and
K_{2} terms to NR_{2} were
identical, either at the basal state or under mechanical and
decongestant treatments, ie, that the
K_{1}/K_{2} ratio in each
condition was about 1:2. Consequently, equation 4 reduces to
Comparison of equation 5 with equation 3 shows that
NR_{2} and NR_{1} are similar NR
estimates, with K = 2K_{2}. This explains why
comparable NR values and NR responses to mechanical or decongestant
treatments are found whether NR is calculated from equation 1 or
equation 2.