Abstract
A knowledge of steady blood mass flow rate in intact large blood vessels may be vital in the clinical environment since it can provide both a direct measure of the quantity of perfusion and also an indication of the energy level of either a limb or an organ. In order to measure blood mass flow rate in this particular case, catheterized thermodynamic flowmeters have been chosen as a result of a survey of blood flowmeters and a theory of thermodynamic blood mass flowmetry has been devised. The most common thermodynamic blood mass flowmeter is probably the so-called local thermal dilution blood mass flowmeter and the main part of the thesis concentrates on this flowmeter. Preliminary investigations on one flowmeter of this type resulted in the re-specification of criteria for the flowmeter. In conjunction with the work on local thermal dilution flowmeters a unique thermodynamic blood flowmeter consisting of a catheterized multi-flow heat exchanger was derived and investigated. A thermally insulated catheter and a fail-safe integrated material construction of catheter and probe have been devised for the local thermal dilution flowmeter both of which factors may be applied to the multi-flow heat exchanger. At various stages of its development the local thermal dilution flowmeter has been tested both in vitro and in vivo and the multi-flow heat exchanger flowmeter tested in vitro only. These experiments are reported in the thesis. The problem of clotting on the catheter and probe and the hydrodynamics of the mixing region are considered for the local thermal dilution flowmeter and a new proposal is cited for this flowmeter.