It's all relative: Usage of relative temporal expressions in triage notes

At the beginning of a patient's visit to the Emergency Department (ED), a record is created containing the Chief Complaint and the Triage Note. The Triage Note attempts to capture the events and circumstances leading up to the decision to visit the ED. Events in the triage note are often not recorded in the order in which they occurred but rather in the order in which they are reported. In addition, patients typically do not use absolute terms to describe the timing of these events. Instead, they rely on relative phrases such as yesterday and this morning. Using a temporal information extraction system, we examine the variation in frequency of these relative temporal expressions over time of day. We then suggest interpretation rules for translating this ‘natural time’ used by people to the ‘logical time’ necessary for the automatic placement of the associated events in the proper sequence on a timeline. The research described here serves as a building block to support the automated creation of timelines with the goal of aiding clinicians and others in visualizing the patterns of events which led to the patient's visit to the Emergency Department.