This work was performed within the "Virtual Emergency Room" (VER) of the "Laboratory for Integrated Medical Interface Technology" (LIMIT) environment at the HITL [34]. The VER consists of a cylindrical space whose walls are texture maps created from video of the local county trauma center. The VER is implemented with Sense8's WorldToolKit, and runs on an SGI Onyx Reality Engine-II computer. The user display is created by Virtual Research VR4 head-mounted displays, and user head tracking is accomplished by a Polhemus Fastrak. The VER is thus a VR "simulation" of an AR medical environment which allows testing of AR constructs within the nonmedical setting of the HITL.
For this study, two ECG monitor object variants and one blood pressure (BP) monitor object were created and added to the VER. These objects were implemented with the WorldToolKit plus a custom 3D graphics library written by Poupyrev and Miller, and are shown in Figure 1.
One ECG monitor variant is a conventional waveform (WF) representation of the ECG rhythm. The other is a novel 3D representation consisting of an iconized version of the cardiac conduction system and chambers. Both models are driven by a common data schema for cardiac rhythms inspired by the work of Widman and Tong [35]. This schema enables the creation of arbitrarily long sequences of different rhythms combined in a seamless fashion. Ten rhythms were implemented:
The BP object displays a simulated mean blood pressure that randomly deviates above and below upper and lower boundaries. The display objects have no "control surfaces" for direct user interactivity. Instead, users' interpretations of displayed information are made verbally and captured by keyboard entries by the investigator. This strategy separates out the information communication performance of the system-the focus of this study-from the larger agenda of interface ergonomics.