A human factors evaluation of auditory displays in medical electrical equipment

Abstract

Auditory alarms have, for the most part, gone unchanged in human technological developmental history. This is largely due to their success and simplicity. As they take advantage of the primitive human principle of fight or flight, they have been found to be a significant attractor of attention, are generally easy to understand, omi-directional, and to the point.Medical staff, for instance, use sounds in many aspects of patient monitoring-the steady beeping of the pulse oximeter, or insistent alarms from equipment when a patient is going critical. However, due to the complex nature of patient care, the sounds that demand the most attention are not always the most useful, and are sometimes detrimental to work, causing annoyance and confusion.Thus the problem is determining the best way to alert medical and nursing staff to changes in a patient's state, provide them with enough information about this change when needed, and not affect their ability to address it and other immediate concerns. For about three decades, the design of effective auditory alarms and displays in the operating room and intensive care unit (ICU) environment has received a significant amount of attention from human factors researchers. Contributing studies on the physical limitations of the auditory channel (Neurobiology and Psychoacoustics), how this information is processed (Cognitive Psychology), and how best to represent the information (Display Engineering) provide a valuable source of information which should inform the design of such displays. How much effect this has had on the industry, however, is debatable, as the design and development of the majority of auditory displays currently in operating rooms seems to have largely ignored these findings.Instead, human factors researchers have found it necessary to perform their evaluations on an ad hoc basis. Often well after the medical systems have been produced and put into use.This thesis presents the findings of a study involving a set of informative melodic medical alarms which has been presented as a design standard for implementation in the International Electrotechnical Commission standard for Medical Electrical Equipment. The goal in providing this design was to provide alarms which not only direct attention, but iii convey simple information encoded within the melody, which communicates to medical practitioners which organ system has entered an abnormal state.In the first 2 experiments, the practicability of the presented alarms as an informative auditory display was evaluated on both novice and professional (practicing nurses) populations. The use of mnemonic learning aids was also examined as these were central to the fundamental design intention of the alarm melodies. The results confirmed participant testimonies that the provided mnemonics did not aid them in identifying alarm labels when presented with the alarm sound, even after prolonged testing over 2 days.Expert knowledge in the domain and knowledge of the context of the menmonics also did not provide any perfor...