Computer-aided investigations of respiratory data

In the first part of this paper a computerised evaluation of plethysmographic signals is presented. The off-line processing described eliminates some erroneous simplifications that routine plethysmography is bound to involve. (1) A subtraction of the box pressure baseline permits measurements with perfectly sealed constant volume plethysmographs even in the case of thermal disequilibrium. (2) Alveolar pressure is computed from the box pressure signal, using instantaneous values of the intrathoracic gas volume. (3) This technique enables one to utilise all the measured data for determinations of airway resistance and viscous work, thus yielding more exact values as compared to the graphic evaluations. In Part 2 a three-parameter model of transpulmonary mechanics, applied to fit data of cat experiments, is described. The aim of this study is to demonstrate how transpulmonary parameters (static pleural pressure, compliance and resistance) are modified by the actual state of the pulmonary vascular bed.