A sound approach to medical alarm design
Hospitals can get noisy, especially intensive care units, and the life-saving electronic machines monitoring patient vital signs are making most of the racket. Mike Rayo, an integrated systems engineering assistant professor at The Ohio State University, is working to improve and organize the cacophony to help caregivers and patients alike.
For almost a decade, Rayo has collaborated on hospital alarm research with human factors and ergonomics experts like Judy Edworthy and Ohio State Professors David Woods and Emily Patterson. Edworthy, a professor of applied psychology at the University of Plymouth, is considered by many to be “the godmother” of auditory alarm design. Rayo calls her a “rock star.”
Rayo’s most recent work, made possible by a P30 Centers grant from the Agency for Healthcare Research and Quality to The Ohio State University Wexner Medical Center (OSUWMC), has allowed him to further alarm research and directly improve patient care. It originated with Rayo contributing to a 2018 research article “Getting Better Hospital Alarm Sounds Into a Global Standard” by Edworthy and others that appeared in Ergonomics in Design: The Quarterly of Human Factors Applications. In this article, they describe the process of first designing and then testing potential audible alarm signals to replace those in the global medical device safety standard, IEC 60601-1-8. They demonstrated that, in all tests, their newly designed alarm signals significantly outperform the current alarm signals.
“Judy brought a large number of us together from different disciplines to understand alarm efficacy in real healthcare situations,” Rayo said. He and other co-authors are also members of an Association for the Advancement of Medical Instrumentation committee, led by Edworthy, to draft the updated IEC 60601-1-8 standard.
Rayo’s current research explores use of the acoustical quality of timbre, the characteristics which allow the ear to distinguish sounds that have the same pitch, tempo and loudness.
“It’s basically the sound quality left when you take out all the other easily described qualities, like pitch, rhythm, frequency and so on,” he explained. “If I play the exact same note at the same pitch for the same duration at the same rhythm on a clarinet, a trumpet and a piano, the human ear can tell the difference.”
His paper “Using timbre to improve performance of larger auditory alarm sets” appeared in late 2019 in the journal Ergonomics. In coordination with the OSUWMC Alarm Taskforce, Rayo and his team compared two sets of alarms in an actual inpatient setting.
In a hospital environment, Rayo estimated that more than ten alarm sources are present in any given room. “Each of those are going to emit a number of alarms,” he explained. “For example, a heart monitor we observed had alarms with multiple timbres.”
Rayo proposed the assignment of a specific timbre to each medical or physiological category of monitor—for example, heart, lungs, brain and so on. Whereas other sound qualities, like frequency or pitch, would signal differences between normalcy and urgency.
The study was conducted in 11 inpatient units at Wexner Medical Center. Alarms were transmitted to inpatient nurses on hand-held devices typical to a modern hospital setting.
His team found that making alarms more acoustically rich by using timbre to convey medical groups and by associating other qualities with urgency improved identifiability and category match.
“Our new set of sounds were perceived as more similar within the alarm groups, facilitated better identification of individual alarm sounds and of alarm groups, and conveyed a wider range of urgency than the baseline sounds,” Rayo explained. The improved, timbre-focused sounds developed by his team are now implemented on Ohio State Wexner Medical Center nurses’ handheld devices (click to hear the alarm sounds).
“I have not heard of another hospital or system that has custom-designed their alarm tones,” he added. “This partnership is somewhere between rare and extremely unique.”
Dr. Susan Moffatt-Bruce, who was the principal investigator on the P30 grant and executive director of OSUWMC University Hospital during the project, added, “This project was pivotal to truly leverage the learning healthcare system and improve patient safety for the entire Wexner Medical Center. This is where human factors experts like Dr. Rayo and Dr. Patterson can improve clinical outcomes and improve healthcare resilience.”
Rayo said his team’s findings also are relevant for other industries that employ a series of alarm sounds.
He believes too many assumptions are made when medical or safety alarms are designed, instead of making design decisions based on data and testing. “One assumption is if something alarms more, it must be alarming better,” he offered. “Another assumption often made by designers is that the alarm sound will be understood by others exactly as they intended and imagined it to be understood.”
Rayo’s collaborators include: Dr. Iahn Gonsenhauser, Jackie Lamendola, Traci Mignery, Dr. Susan Moffatt-Bruce, Todd Yamokoski and Lynette Roush of Ohio State Wexner Medical Center; School of Health and Rehabilitation Sciences Associate Professor Emily Patterson; Cognitive Systems Engineering Laboratory Research Associate Morgan Fitzgerald; and Lextant User Experience Design Director Steve Simula.
