[Computerized measurement and modelling of the pulmonary pressure-volume curve (author's transl)]

The authors studied the expiratory transpulmonary pressure-pulmonary volume (PV) curve obtained under quasi-state conditions in a population of 20 pathological subjects. The signals were processed digitally using a microcomputer. A "filtering" of the curve made it possible to discard the points corresponding to sudden pressure variations resulting from oesophageal peristalsis. Then the data were processed using the different models proposed in the literature to define the shape of the PV curve. The best fit was obtained with the hyperbolo-sigmoidal model proposed by MURPHY and ENGEL [39]. This is due to a general characteristic of curve modelling : the quality of the fit is closely related to the number of parameters. However, except for the asymptotes VM and Vm, the five parameters of the hyperbolo-sigmoidal model have no physiological meaning. Another reason for this model being particularly successful is that it fits well sigmoidal curves and that we studied the PV curve from total lung capacity to residual volume, that is on a volume range where the curve may be much sigmoidal in pathological cases. Finally, this study showed that the use of this model can be simplified and allows to determine automatically lung compliance at any point of the PV curve. The method can be used easily in any laboratory where routine functional examinations are performed.