Transoesophageal Doppler: TOD
Transoesophageal Doppler (TOD), supports a CW sensor on the end of a probe which is be introduced via the mouth or nose and positioned in the oesophagus so the Doppler beam aligns with the descending thoracic aorta (DTA) at a known angle. Because the transducer is close to the blood flow the signal is clear, however correct alignment may be difficult to maintain, especially during patient movement. This method has good validation, particularly for measuring changes in blood flow wihth outcomes evidence for intra-operative monitoring. However it only measures DTA flow and not true Q, and this may be potentially influenced by disproportionate changes in blood flow between upper and lower body, though this is only important at low and high Qs. This method generally requires patient sedation and is accepted for use in both adults and older children.
Read more about this topic: Cardiac Input, Measuring Cardiac Output, Doppler Ultrasound Method
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