Pulsoxymetrie in der Transösophagealen Echokardiographie

Pulse oxymetry in transoesophageal echocardiography. Pulse oxymetry to assess oxygen saturation is an important diagnostic tool in medicine and plays a central role in monitoring patients undergoing invasive or semi invasive examinations like for instance transoesophageal echocardiography. The examiners thorough understanding of the functional principle, the limits, the value and potential reasons of changes of the results are pivotal for a correct imterpretation of the findings and therefore for diagnosis and therapy of the patient. Hypoxaemia or technical failure can – among others – be responsible for low values of oxygen saturation. False interpretation of oxygen saturation can be caused by abnormal haemoglobin or a shift of the oxyhaemoglobin dissociation curve. A low oxygen saturation at the beginning of the examination is most commonly due to a technical failure or a ventilation problem, once, these reasons are exluded, the examiner needs to consider a cyanotic heart disease and has to search for it actively. If decreasing oxygen saturation is observed during the examination hypoventilation needs to be excluded first (level of sedation, lung pathology). Furthermore a formation of methaemoglobin due to throat anaesthesia needs to be considered.