A laboratory evaluation of an auditory display designed to enhance intraoperative monitoring

Encouraged by the popularity of the pulse oximeter pulse-tone, we developed and tested an auditory display of six physiologic variables. The display consisted of a cardiovascular sound triggered by every heartbeat (conveying heart rate) and a respiratory sound triggered by every breath (conveying respiratory rate). Attributes of the cardiovascular sound were modulated to convey hemoglobin saturation and blood pressure, and those of the respiratory sound were modulated to denote end-tidal CO₂ and tidal volume. Three display formats (auditory, visual, and combined) were compared. Fourteen anesthesia residents monitored dynamic displays of 6 variables to detect and identify 6 predefined events during 21 trials. An event occurred during each trial and the subject's task was to detect when it started and then identify the type of event. Subjects detected every event. They detected events more rapidly with the combined display (10.4 s) than with the visual (12.8 s) or auditory (13.0 s) displays. Subjects correctly identified events least often with the auditory display (60% versus visual 88% and combined 80%). They correctly identified events more quickly with the combined display than with the visual display. We conclude that, with little training, clinicians can successfully detect and identify simulated clinical events using an auditory display of six variables.