Point:counterpoint Comments

To the Editor: Mitzner argues that constant phase modeling is not more useful that simpler methods and no research has substantiated the importance of several variables determined by constant phase modeling (6). This is untrue and indicates only a cursory attempt at a literature review. We clearly established a developmental pattern in normal healthy newborn rat pups where PV curves, tissue damping (G), elastance, and hysteresivity (eta) all change from days 10 to 17 (2). In particular, eta was found to change in a PEEP-sensitive manner consistent with the development of mature secretory cell lung function. Furthermore, we showed an alteration in this developmental pattern, particularly with G, static compliance, elastance, and airway resistance with CFTR gene expression levels (3, 4). Combined PV and constant phase modeling were essential to substantiating these conclusions. Hysteresivity, G, and other constant phase parameters serve as sensitive developmental markers for pathology before histologic effects (4, 5). Thus, while we are still relating these parameters to specific structural and cellular changes, they become invaluable tools for identification of subtle gene developmental effects and as confirmation of PV curve changes. This is particularly important when dealing with new findings in controversial topics such as the role of CFTR in lung development. Ockham’s Razor states “all things being equal the simplest explanation tends to be correct,” not the simplest data tends to be the most useful. As we seek to understand disease processes and pathophysiology, the more detailed information of constant phase modeling is simply better.