Many attempts have been made to quantify cardiac output using both invasive and
non-invasive techniques. The results have generally been poorly reproducible
and comparisons of techniques have yielded highly variable values.
A single breath inert gas method was used in the study, since it offers several
advantages over previous methods, chiefly its speed of measurement, and the
controlled manner in which it is performed. The method observes the uptake of a
semi-soluble inert gas (Freon-22) with respect to an insoluble marker, and
calculates cardiac output (pulmonary flow) from the slope of the semi-soluble
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy at Loughborough University.