title: A simplified procedure for exponential fitting of pressure-volume curves of normal and diseased lungs.
abstract: Exponential fitting of mammalian pressure-volume curves requires least squares approaches, using computer facilities. We have developed a simplified fit procedure which can be performed by hand or by a small pocket calculator. First the asymptotic value of the volume axis, Vm, is estimated from a series of volume data at equal pressure-intervals. Subsequently, the 'pressure constant' (comparable with a time constant) and the intersection of the curve with the pressure axis (Po) are determined graphically. A comparison of the fit parameters with those obtained from a non-linear least squares procedure, performed on a medium-size computer, yielded an accuracy sufficient for practical purposes. We conclude that the simplified fit procedure may be a valuable tool for a quick and accurate interpretation of mammalian pressure-volume curves in pulmonary function routine.
mesh_terms: D001699:Biometry; D006801:Humans; D008168:Lung / Q000033:anatomy & histology / Q000502:physiology*; D008171:Lung Diseases / Q000473:pathology / Q000503:physiopathology*; D008176:Lung Volume Measurements; D008954:Models, Biological; D011312:Pressure