The aim of this work is to develop new methods able to evaluate the non-linear effects in respiratory resistance. Such methods may provide valuable information about the underlying pathophysiology of respiratory diseases and help guide treatment decisions. After a description of the used procedures, an in vivo study showed significant differences in non linearities evaluating normals and patients with airway obstruction (p = 0.001). These results are in close agreement with the involved physiology. In addition, the derived parameters allowed adequate diagnostic accuracy (area under the receiver operating characteristic curve of 0.93, sensibility of 0.80, and specificity of 1.00). These results confirms the high scientific and clinical potential of evaluating nonlinearities in respiratory resistance.