Comment on “Study of mixed-mode oscillations in a nonlinear cardiovascular system” [Nonlinear Dyn, doi: 10.1007/s11071-020-05612-8]

This note comments on the questionable approach and claims made in “Study of mixed-mode oscillations in a nonlinear cardiovascular system” [Nonlinear Dyn, doi: 10.1007/s11071-020-05612-8]. Although the author of the above paper attempts to discuss a nonlinear cardiovascular system and its dynamics, the conductance model used, is that of the well-known Cassie–Mayr model of electric arcs, known in the literature since the 1940s. No reference to that well-known model is made however. Moreover, the claim that the conductance model is taken “from the data of a large patient population” is baseless and has no grounds in reality. Thus, an extreme caution is advised, when analyzing the time responses and properties of the nonlinear model in the commented paper. It is questionable that they represent quantities of a human cardiovascular system.