Motivation\ud
Our study is designed to identify human factors that are a threat to the safety of children with heart disease.\ud
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Research approach\ud
After an initial observation period, we will apply a major safety intervention. We will then re-measure the occurrence and types of human factors in the operating room, and the incidence of adverse events, near misses and hospital death, to evaluate if there was a significant post-intervention reduction. \ud
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Findings/design\ud
We focus on challenges encountered during the training of the observers. Research Limitations\ud
Because of the complexity of the OR, observations are necessarily subjective. \ud
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Originality/Value\ud
This work is original because of the systematic evaluation of a safety intevention and the training protocol for the observers.\ud
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Take Away Message\ud
Systematic and periodic assessment of observers is required when teamwork is observed in complex, dynamic settings