A field approach to thoracic impedance plethysmography

Electrical impedance measurement has not gained wide acceptance as a reliable method for quantifying intra-thoracic events because the mechanisms behind impedance changes are not sufficiently well understood. At the outset of the research reported in this thesis the intention was to simulate these mechanisms in an attempt to determine the individual components of the impedance waveform. However, some preliminary investigation into the application of commonly used instrumentation raised questions about the suitability of impedance to three-dimensional situations, and indicated that a more general philosophy was required. This is provided by a treatment of the measurement situation in terms of vector fields rather than scalar impedance. This field approach is developed both theoretically and practically, using a thorax model based on an anatomical atlas. Simulated examples illustrating the properties of the field approach are given, including a demonstration of its ability to distinguish simultaneous events - generally impossible through impedance measurement alone.