Objectives: To determine (1) the proportion and number of clinically relevant alarms based on the type of monitoring device; (2) whether patient clinical severity, based on the sequential organ failure assessment (SOFA) score, affects the proportion of clinically relevant alarms and to suggest; (3) methods for reducing clinically irrelevant alarms in an intensive care unit (ICU). Design: A prospective, observational clinical study. Setting: A medical ICU at the University of Tokyo Hospital in Tokyo, Japan. Participants: All patients who were admitted directly to the ICU, aged ≥18 years, and not refused active treatment were registered between January and February 2012. Methods: The alarms, alarm settings, alarm messages, waveforms and video recordings were acquired in real time and saved continuously. All alarms were annotated with respect to technical and clinical validity. Results: 18 ICU patients were monitored. During 2697 patient-monitored hours, 11 591 alarms were annotated. Only 740 (6.4%) alarms were considered to be clinically relevant. The monitoring devices that triggered alarms the most often were the direct measurement of arterial pressure (33.5%), oxygen saturation (24.2%), and electrocardiogram (22.9%). The numbers of relevant alarms were 12.4% (direct measurement of arterial pressure), 2.4% (oxygen saturation) and 5.3% (electrocardiogram). Positive correlations were established between patient clinical severities and the proportion of relevant alarms. The total number of irrelevant alarms could be reduced by 21.4% by evaluating their technical relevance. Conclusions: We demonstrated that (1) the types of devices that alarm the most frequently were direct measurements of arterial pressure, oxygen saturation and ECG, and most of those alarms were not clinically relevant; (2) the proportion of clinically relevant alarms decreased as the patients' status improved and (3) the irrelevance alarms can be considerably reduced by evaluating their technical relevance.
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