Error in clinical measurement

Abstract While monitoring systems have undoubtedly reduced the morbidity and mortality associated with anaesthesia, the principal patient monitor should be the close observation of vital signs by a trained anaesthetist. All monitors appear to provide accurate useful information. However, the values displayed may often not reflect the true state of the patient, or not even reflect the desired information. Errors may be seen across the full range of measurement (systematic) or only under certain conditions (contextual). The best solution to these problems is for anaesthetists to have a sound understanding of how each monitor works and the conditions under which its outputs may become inaccurate.