Effect of Co-Alarming of Monitor Alarms on the Response Time and Accuracy of Recognition of Novel Hemodynamic Alarms

In the high-stakes environments of hospitals, where monitors beep and flash to signal a patient's changing condition, sound is a vital language. These auditory alarms are designed to cut through the noise of a busy ward and alert doctors and nurses to life-threatening shifts in a patient's heart rate or blood pressure. However, when too many devices sound at once, or when the sounds themselves are difficult to tell apart, the human ear and brain can become overwhelmed. This phenomenon, known as alarm fatigue, occurs when clinicians become so accustomed to a constant stream of alerts that they may miss a critical signal or respond too slowly. The challenge for engineers and medical researchers is to design sounds that are not only loud enough to be heard but are also structured in a way that the brain can instantly recognize what is wrong and how urgent the situation is, even when competing noises are present.

A team of researchers set out to test a new approach to these critical sounds, focusing on how the structure of an alarm affects how quickly and accurately a person can identify it. They created new auditory signals for heart rate and blood pressure that were built on principles of human hearing, specifically using sounds that intuitively mimic the physiological event they represent. For heart rate, they incorporated a "lub-dub" sound that mimics a heartbeat, followed by a rapid sequence of tones to signal urgency, and finally a pitch that moves up or down to indicate whether the heart is beating too fast or too slow. They tested these new sounds alongside the standard alarms currently used by major medical equipment manufacturers, which often share similar melodic structures. The goal was to see if these new, perceptually informed designs could remain clear and distinct even when the familiar, proprietary alarms were sounding at the same time.

To conduct this test, the researchers brought thirty-nine healthy adults into a quiet laboratory. These participants were not medical professionals, but they were asked to perform a task that simulated the mental load of a busy clinical setting. While wearing headphones, they listened for specific alarms and had to identify whether they were hearing a high or low heart rate, or a high or low blood pressure. To make the task more challenging and realistic, the participants also had to perform a secondary visual task on a computer screen, pressing a key whenever a specific letter appeared. This dual-task setup ensured that their attention was divided, much like a clinician monitoring a patient while performing other duties. The alarms were played in two main scenarios: first, in isolation, and second, mixed with the standard alarms from General Electric and Philips, which served as competing background noise.

The results revealed that the brain processes different types of medical alarms at different speeds. When the new heart rate alarms were played alone, participants took longer to identify them compared to the new blood pressure alarms. On average, the response to the heart rate sounds was 763 milliseconds slower. The researchers found that this delay was likely due to the timing of the information within the sound itself. The blood pressure alarms provided their most important clues right at the beginning, allowing for a quicker decision. In contrast, the heart rate alarms required the listener to wait for the full sequence of sounds to unfold before the direction of the change—whether the heart was speeding up or slowing down—became clear.

When the researchers introduced the competing alarms from the major manufacturers, the difficulty increased for everyone. The presence of these background sounds slowed down the participants' reaction times by 89 milliseconds and reduced their accuracy by 4 percent. This drop in performance suggests that even well-designed new sounds can be partially obscured by the existing clutter of hospital noise. However, the study also uncovered a specific nuance in how the direction of the sound mattered. When the heart rate alarm indicated a rising heart rate, the presence of a competing alarm made the response 183 milliseconds slower. In contrast, when the alarm indicated a falling heart rate, the delay was negligible, only 4 milliseconds. This difference appears to be linked to the frequency of the sounds; the rising pitch of the fast heart rate alarm occupied a similar range of frequencies as the standard high-priority alarms from the manufacturers, causing them to interfere with one another more than the lower-pitched sounds of the slowing heart rate.

The study concludes that while these new alarm designs show promise, they are not yet perfect for the chaotic reality of a hospital room. The findings suggest that the timing of when a sound delivers its most critical information is just as important as the sound itself. By front-loading the most urgent cues, designers could potentially help clinicians make faster decisions. The research also highlights that the specific pitch and frequency of an alarm can determine whether it gets lost in the noise of other equipment. While the delays observed in the lab were measured in fractions of a second, in a clinical setting, even a brief hesitation can impact patient care. The authors suggest that future work should focus on refining these sounds to ensure they remain distinct and recognizable, even when the hospital is at its noisiest, and that these designs should eventually be tested with actual medical professionals to confirm their effectiveness in real-world scenarios.