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Improving Device Noise Control

By Mike Bassett

Researchers are making efforts to reduce noise arising from medical device alarms that distress patients, interrupt their sleep, and may have long-term consequences.

It's no secret that patients in health care facilities, eg, hospitals and nursing homes, are likely to experience poor sleep quality.

Whether it's because of the never-ending sounds of medical device alarms or noise arising from health care providers and other patients, patients constantly experience sleep disruptions, and that can seriously affect even the most vigorous individuals.

Medical device alarms are a particular problem. "They distress the patient and interrupt their sleep," says Joseph Schlesinger, MD, an assistant professor of anesthesia in the division of critical care medicine at Vanderbilt University Medical Center in Nashville. "And as patients get their sleep disrupted it can be a precipitant for delirium and even PTSD (post-traumatic stress disorder) related to a critical illness."

And when considering older patients, "You are talking about patients who may be already experiencing some cognitive decline," he adds. "And putting them in an abrasive acoustic environment is not going to help."

With that in mind, Schlesinger asked himself: Is it really necessary for a patient to hear all of these alarms?

Necessary Part of Operations
Medical device alarms are ubiquitous in a hospital setting. As Schlesinger points out, medicine is a "high consequence" industry. If mistakes are made, the consequences can be severe. Medical device alarms are meant to guard against these potential medical catastrophes.          

But the problem with these alarms is that they are often clinically irrelevant or simply false alarms. The result of this acoustic overload is "alarm fatigue."

"We hear alarms all the time and because they're often false, our attitudes toward them can be lackadaisical, and that can create a really bad perception [for the patient] concerning quality of care," Schlesinger says. "But if you do respond to the alarm, then it disturbs the patient." So he began mulling over a way to remove at least some of the noise from the patient environment.

Simply silencing an alarm isn't an answer because it's dangerous—sometimes it's a real alarm, and physicians need to hear it. And while providing patients with earplugs and eye masks may be a temporary solution, it doesn't work in the long run. "Human beings are used to environmental stimuli," Schlesinger points out. "Take it all away and you have a very abnormal environment. And the concern there is that it can cause delirium."

As a proof of concept, Schlesinger decided to focus on one alarm—the patient monitor red/crisis alarm that's found in every hospital intensive care unit—to see whether it would be possible to apply some kind of filter that would eliminate that single noise from the patient's environment.

Possible Solution
Working with students at Vanderbilt's department of biomedical engineering, Schlesinger designed a "frequency-selection silencing device" that uses Raspberry Pi (a single-board, low-cost, high-performance computer) and digital filters to remove the alarm sound while transmitting other sounds, such as voices, into an inner ear headphone without distortion.

"My big concern was that I wanted to make sure we didn't affect human speech," he says. "We wanted to make these filters but make sure that speech was preserved."

Schlesinger and his team tested the prototype in an ICU-type environment and performed what he called a "speech intelligibility task." The results of that test—presented earlier this year at the International Conference on Auditory Display—showed that not only was speech preserved while filtering out the alarm noise, but that speech comprehension actually improved as well.

"We were truly able to take the alarm out, improve the quality of speech, and improve the actual objective score on that speech task," Schlesinger says. "Our research participants said that they felt much less stress when the alarm was taken out of their environment. So subjectively and objectively we had very positive results."

Schlesinger's research is an exciting and innovative approach to the problem of excessive noise in health care settings, says Erica Ryherd, PhD, an associate professor of architectural engineering at the University of Nebraska and a specialist in health care design. "But one of my concerns is that in addition to alarms, there are a lot of problematic noise sources in hospitals."

These noise sources can include staff, other patients, medical, service and maintenance equipment, and even noise coming from outside of a facility, Ryherd says. "We really have to think about everything, not just alarms."

Guidelines exist regarding maximum noise levels in hospitals. The World Health Organization, for example, recommends that noise levels in ICUs should average 35 decibels during the day and 30 decibels at night. Studies have shown, however, that noise levels often exceed those recommendations.

A 2016 article in BMJ found that noise levels in five hospital ICUs in the United Kingdom were just under 60 decibels during the day (with peaks of 100 decibels), and while slightly quieter at night, still experienced peak decibel levels above 85. And while alarms and staff activities were the primary sources of noise disturbance in ICUs, noise from other patients and infrastructure were prime contributors as well.

But things are improving, Ryherd says. "In the last 10 years we've really seen a surge around the idea of making not just hospitals, but all health care environments quieter. This all takes time because we have to do the research, develop the right products, get the right technology in place, and make sure it all works with staff and patients."

Ryherd says health care facilities are taking what she refers to as physical and administrative approaches to reducing noise that are being used with varying degrees of success.

"You can make changes to the physical environment." she says. "Reduce the sources of noise, add acoustic treatments [to absorb noise], and think about the envelope—you don't want sound passing between rooms or from the outside. All of these things require physical and environmental changes and are pretty successful if done right."

Administrative approaches, such as developing "quiet time" protocols for hospital staff, usually involve efforts among staff to reduce noise and promote patient rest. "There has been a lot of improvement [in reducing noise levels]," Ryherd says. "But there's more that needs to be done."

Additional Innovation
According to Schlesinger, who is also a research member of the Centre for Interdisciplinary Research in Music Media and Technology and an adjunct professor of electrical and computer engineering at McGill University in Montreal, Canada, the ultimate goal is the development, in collaboration with his colleagues in Montreal, of a wireless inner ear headphone that will perform the necessary noise filtering as well as the transmission of the filtered sound into the device itself.

Schlesinger says that one area of focus in developing the device is comfort. "Often when people develop inner ear devices, they don't think about comfort; they just think about function," he points out. "When you get ear buds with a new cell phone, the thought is function, not comfort, because no one is going to wear them two days in a row. So we're working on a comfortable inner ear device."

And the device doesn't have to be extraordinarily expensive, Schlesinger says. "We were super-aggressive in making [the prototype] as cheaply as possible." According to Schlesinger, the total cost of the prototype used in his study was about $250. "We were trying to prove a point," he says. "We could take the alarm out and improve speech inexpensively."

As for getting a device on the market and into hospitals, that will take some time, Schlesinger says, adding that more research is needed regarding the use of the device and patient outcomes, benefits, and safety. These kinds of studies take time "because you need a lot of them to get statistical significance," he says. "And there are a whole host of inclusion and exclusion criteria, especially with critically ill and geriatric patients."

Fortunately, he says, his research and findings have garnered a lot of attention, so he's hopeful that other academic research sites well be interested in collaborating with him, which will help complete the research/study phase as quickly as possible. Schlesinger believes the demand is there for such a device.

"As medicine improves, we are getting more and more people out of the hospital alive, but with all these neuropsychological issues," he says. "When you get ICU delirium, it can lead to long-term cognitive impairment, and you're not the same person you were—especially in the geriatric population.

"We need to do as much as we can about modifiable risk factors," he adds. "We can't change age or sex or comorbidities, but if we can change modifiable risk factors—and sound exposure levels are absolutely modifiable—once the data come out, I think there will be a huge demand [for such a device]."

— Mike Bassett is a freelance writer based in Holliston, Massachusetts.