Confidence bounds on respiratory mechanical properties estimated from transfer versus input impedance in humans versus dogs

A sensitivity analysis is used to determine whether and why the six-element model of A.B. Dubois et al. (1956) could be applicable to lower-frequency (<64 Hz) transfer impedance, Z _tr, data in humans, but not input impedance, Z _in, data over any frequency range. The joint parameter uncertainty bounds are predicted, assuming a fit to either 2-32-Hz Z _in or Z _tr data created from literature-based mean parameter values. It was predicted that the estimates will be very unreliable if obtained from Z _in data for humans or dogs, or from Z _tr data from dogs. Surprisingly, however, the reliability of several parameter estimates from human Z _tr data from only 2-32 Hz are reasonable. The variability in 2-62-Hz-based Z _tr parameter estimates is evaluated by comparing experimental variability in two healthy human subjects to theoretical and Monte Carlo numerical predictions based on a single trial. Again, the Z _tr parameters were reliable. A simulation study was used to describe the reasons for enhanced reliability when using human Z _tr data.