PDPS: a pulmonary data processing system for assessment of gas exchange properties by multiple gas wash-out

A data acquisition and processing system for the analysis of inert gas wash-out tests is described. The described system is in clinical use on spontaneously breathing patients as well as on mechanically ventilated Intensive Care patients. It combines several analysis techniques with an aim to provide a deeper insight into the nature of existing ventilation inhomogeneity than the individual techniques alone can provide. The signals measured are the respiratory flow, the fractions of one or two indicator gases washing out and the fractions of the metabolic gases oxygen and carbon dioxide. Analysis of these signals provides information concerning the end-expiratory lung-volume, distribution of ventilation and perfusion in the lung, the role of diffusion in the ventilation process and the metabolic oxygen uptake and CO2 release. This article describes the algorithms used and the results that are presented.