Ans. b. Stewart-Hamilton equation (Ref: Ganong 23/e p513; Guyton 11/e p244)Stewrt-Hamilton equation is the basis for thermodilution method used in measurement of cardiac output by pulmonary catheter.Stewart Hamilton equationThe thermodilution technique has become the de-facto clinical standard for measuring cardiac output because of its ease of implementation and the long clinical experience using it in various settings.It is a variant of the indicator dilution methodQ, in which a known amount of a substance is injected into peripheral vein and its concentration change measured over time in serial arterial samples.As its name implies, the thermodilution method uses a thermal indicator, whereas other indicator dilution methods use various substances, such as indocyanine green dye.The fundamental physical basis for the indicator dilution method is given by the Stewart-Hamilton equationQ, named after the two investigators who were instrumental in the development of this technique.