An electromagnetic flowmeter for studying changes of cardiac output in unanaesthetized rats

An electromagnetic flowmeter is described which has been designed for the determination of cardiac output changes in the unanaesthetized rat, over a period of weeks. The construction and form of the implanted flow probe and associated electronic equipment are discussed, together with their limitations and main sources of error. To establish the validity of the method, comparisons are made of the flowmeter output with a standard method inin vitro andin vivo tests. The results of these comparisons have shown a linear relationship between the flowmeter readings and absolute values of flow rate. Furthermore, they show a difference betweenin vitro andin vivo sensitivity of the probe, the reasons for which are discussed.