Originally Published MDDI October 2001ALARMS Industry sounds off on a new document aimed at standardizing the design of alarm systems for use in medical equipment.Michael E. Wiklund and Eric A. Smith

October 1, 2001

12 Min Read
Answering the Call for Harmonization of Medical Device Alarms

Originally Published MDDI October 2001


Industry sounds off on a new document aimed at standardizing the design of alarm systems for use in medical equipment.

Michael E. Wiklund and Eric A. Smith

0110d118a.jpgTo many medical device manufacturers, the notion of a medical device alarm standard is, well. . . alarming. That the draft of a standard jointly developed by the International Electrotechnical Commission (IEC) and ISO has grown to more than 60 pages in length is more alarming still. After all, one might ask, shouldn't alarms be simple? Is there really that much to say about designing an effective alarm system? Couldn't the basics be covered in just a few pages, and the rest be left to the designers?

Designing an effective alarm system is not so simple, though the end result should be. For starters, there are numerous design options to consider, such as auditory alarms, visual alarms, and combinations of the two ( e.g., a flashing light accompanied by a beep). One can even annunciate a warning with a tactile cue, similar to the way a pager vibrates to draw attention in a noisy environment or to avoid distracting others.

To complicate matters further, designers must consider the varying degrees of alarm required to alert users to conditions ranging from minor concerns to deadly threats. There are alarms that signal active problems, such as a dangerous arrhythmia, and those that indicate such a problem has occurred and has already righted itself.

When one factors in the wide variety of medical devices currently in use and the needs of a multidisciplinary, multicultural, global user population, the development of a standard of any length seems like quite an accomplishment.

The emergence of an alarm standard draft reflects the medical device industry's overall desire for harmonization, fueled by anxiety about clinical mishaps. One could draw an analogy to the standardization of traffic signals and road signs: Americans are well served by the red, yellow, and green traffic-light convention, as well as the common stop and yield signs. If these visual cues varied from one state to another, one city to another, or even one intersection to another, chaos and more traffic accidents would likely ensue.

Just as harmonization makes drivers' lives easier, so should harmonized alarms make medical workers' lives easier. And, in contrast to the variation in the style of traffic lights and signage from nation to nation, the harmonization of alarms will be global, theoretically enabling manufacturers to develop one alarm system for all markets.

Again, the standard under development is an initiative of ISO and IEC. The document, which is expected to constitute the eighth collateral standard to IEC 60601-1: Medical Electrical Equipment—Part 1: General Requirements for Safety, is titled "General Requirements and Guidelines for the Application of Alarms in Medical Electrical Equipment." A joint working group of ISO Technical Committee 121, Subcommittee 3, and IEC Technical Committee 62, Subcommittee 62A, began work on the collateral standard in 1997. Current plans call for the final standard's release in another year or so.

The group's second working draft, circulated in December 2000, generated an unusually large number of comments from the medical device development community. Many of the comments were highly critical of the first-of-its-kind standard, and, in some cases, indicated the need for major reorganization. The group met for a third time in Vancouver this past July, and again this September in Andover, MA, to continue working toward a revised draft for public comment. At press time, the next meeting was scheduled for March of next year, in London.


The need for an alarm-system standard is strong. A general inconsistency among devices, coupled with the human-factors shortcomings of some alarm systems, presents major headaches for users. The draft standard's introduction highlights these problems, stating, "Surveys of healthcare personnel have indicated widespread discontent with alarm signals. Problems include difficulty in identifying the source of the alarm signal, loud and distracting alarm signals, and high incidences of false-positive or -negative alarm conditions. . . Often, alarm signals are more confusing than enlightening. Many operators respond to alarm signals by disabling the alarm system or by adjusting a[n] alarm limit to a[n] extreme value that effectively disables the alarm system."

Currently, medical workers must learn the characteristics of each medical device's alarm and be able to differentiate between them. For example, one device may announce an alarm condition with a rapidly flashing red light and a repeating beep, while another might emit a steady amber light accompanied by a set of ascending tones. Workers may also struggle to understand the nuances of the more sophisticated alarm systems. The distinctions between "alarm silenced," "audio inhibited," and "audio suspended," for example, are difficult to discern.

Alarm-system design shortcomings are more than a mere nuisance. Inadequacies can lead directly or indirectly to patient injury and death, as can habits developed by workers to avoid the distraction of false alarms, such as turning the alarm system off entirely. While making alarm systems better may not head the list of remedial actions taken to save lives, it certainly stands to make a positive difference.


The alarm design standard evolved in part from guidance provided in three existing ISO documents: ISO 9703: Anaesthesia and Respiratory Care Alarm Signals—Part 1:1992: Visual Alarm Signals, Part 2:1994: Auditory Alarm Signals, and Part 3:1998: Guidance on Application of Alarms. It covers a wide range of alarm-system design characteristics, including:

  • Activation states.

  • Prioritization.

  • Annunciation.

  • Auditory signaling.

  • Visual signaling.

  • Remote signaling.

  • Limit setting.

  • Alarm resetting.

  • Data logging.

Portions of the draft standard are quite detailed, leaving little to designer discretion. For example, one particular part of the document states that alarm systems should include at least four auditory alarm-signal harmonic components within the range of 300 to 4000 Hz. It recommends that a high-priority alarm indicator light be red and flash at a frequency of 1.4 to 2.8 Hz, with a duty cycle of 20 to 60%. Other parts of the standard are more open to interpretation in that they establish basic requirements but leave the details up to the designers.


The large number of comments on the draft standard was not surprising, considering the significant impact the standard will have on medical device design practices. Manufacturers spend considerable time and money developing and validating their proprietary alarm systems, some as brand-specific as the company's logo. As a result, device companies are naturally protective of their approaches to alarm design and what they perceive to be good for customers and for gaining a competitive advantage.

Carl Pantiskas, a clinical engineer at Spacelabs Medical (Redmond, WA) who has reviewed and commented on the draft standard, concurs. He states, "Spacelabs Medical has put a lot of thought into the design of alarm systems for [its] patient monitors. I would expect any organization that has a good solution—one that has been validated through years of effective clinical use—to be somewhat reluctant to change it to something that may not have gone through the same rigorous validation. You'd have to question whether [the standard was] actually improving things." That said, Pantiskas acknowledges the overarching value of alarm-system harmonization, adding, "I fundamentally believe that an alarm standard is necessary, just as long as the standard is realistic and does not restrict technological innovation."

Pantiskas's specific concern is that the draft as it is currently written does not fully account for the entire range of medical device use scenarios, including the use of devices in the home, and the technological options available to alarm designers. He points out, for example, that the standard should take into consideration the needs of the hearing impaired. He also anticipates that new technologies and applications, such as those found in telemedicine, may introduce alarm-system design issues that transcend the device-focused guidance in the standard. Moreover, Pantiskas worries that the guidance might not be relevant to networked devices or devices warranting advanced alarm-system designs.

Pantiskas's concerns match several others in the body of comments on the standard, so those responsible for the draft—who may feel that the standard already addresses a wide variety of use scenarios—will need to reopen their discussion. Such deliberation is representative of the nature of any collaborative effort to develop and refine a common standard. The creative tension between professionals with differing and sincere viewpoints ensures that the final standard will reflect myriad compromises but will ultimately be good for the industry.


Patterns emerge within the voluminous comments on the draft standard. Some reviewers find the document complex and hard to follow, which suggests the need for extensive reformatting. Some argue that the alarm-system requirements are laden with overly specific design recommendations. Others see the draft stand-ard as being too focused on medical equipment that is closely attended—devices used in the operating room, for example—at the expense of equipment that is typically attended less vigilantly, like that used in acute-care settings. Still others are concerned with the standard's attention to usability design characteristics considered by some to be unrelated to patient safety. A few believe that the standard is better suited to the characteristics of complex devices than those of simpler ones. Another criticism is that the drafters of the document try too hard to "teach" readers about the human-factors engineering of alarm systems.

Within the committee itself, there reportedly is considerable debate on the value of adding an informative annex to the standard that prescribes a set of eight alarm sounds. The idea behind the appendix is that alarm conditions associated with medical devices can be divided into logical categories, each with its own unique alarm sound. The categories, as outlined in the appendix, are:

  • General.

  • Cardiac.

  • Perfusion.

  • Ventilation.

  • Oxygen.

  • Temperature/energy.

  • Drug or fluid.

  • Equipment or supply failure.

As such, a ventilator alarm would sound different than an infusion pump alarm, and a clinician would know instinctively where to look, once the disparate sounds become familiar.

In the appendix, each category is assigned a series of musical notes (a, b, c, d, e, f, and g) designed to be easily distinguishable from one another. High- and medium-priority alarms would be annunciated by a series of five and three notes, respectively.

A high-priority cardiac alarm, for instance, would be annunciated by the series: c, e, g, g, C (the small c and large C denote the same note, one octave apart). The alarm-sound designers intend users to map the syllables of the phrase cardiac alarm to the notes. Accordingly, the mapping would be as follows: c = car; e = di; g = ac; g = a; C = larm. The overall sound would be comparable to a trumpet call or the National Broadcasting Company's familiar television chime.

Whether this kind of mapping will produce real benefits, particularly among medical workers who do not speak English, is uncertain. Yet it seems reasonable to assume that the operators of the equipment would come to associate tones with their appropriate equipment type.

Stephen Dain, MD, a practicing anesthesiologist at the London Health Sciences Centre (London, ON, Canada) who has contributed substantially to the draft standard, firmly believes in the syllable-mapping approach to annunciating an audible warning. But he acknowledges another significant concern about the eight-tone concept, one that has caused intense committee debate about the appendix and could ultimately lead to its exclusion from the standard. Dain states, "The recommended sounds have not been sufficiently validated. We don't know for sure if they are the best possible tones or whether or not users will be able to differentiate between them and correctly associate them with specific equipment. We need to do the user research. But, if we don't take this approach, alarm systems will share the exact same tones, making it more difficult to isolate a particular alarm."


Figure 1. A sampling of recommended alarm symbols.

Similar concerns persist regarding a set of recommended alarm symbols, such as those shown in Figure 1. When the authors of the draft standard conducted an industry-funded study of potential device users to determine the symbols' reliability, they found that many clinicians experienced difficulty understanding and differentiating the symbols—a finding that was passed along to the technical committee. The study underscored the importance of validation testing as a prelude to standardization.


When IEC releases the final standard, it might be incorporated directly into the third edition of IEC 60601. More likely, it will be issued as a collateral standard to the second edition of IEC 60601. Either way, the final document will wield the power of a voluntary standard that reflects the industry's consensus on best practices. It will not have the power of government regulations, and, as such, manufacturers will not necessarily be required to comply with it. Rather, manufacturers can continue developing products that incorporate proprietary alarm systems, but they will do so at their own risk. One such risk for a device manufacturer is becoming the target of a product liability claim that points to a noncompliant alarm system as the cause of injury. There is also the risk that customers will gravitate toward compliant devices—and away from noncompliant ones—to establish alarm-system consistency within their institutions.

According to common practice, existing medical devices would likely be grandfathered, meaning their alarm systems would not be subject to the new standard. The principle of grandfathering is somewhat complicated, however, by the fact that alarm-system behavior is often controlled by software, a device component that is updated over time. This means that some existing medical devices could be updated to comply with the new standard. Thus, one can expect some manufacturers to make the updates to existing medical devices, if only to maintain product-line consistency.

Interestingly, the draft standard permits manufacturers to replace the recommended alarm sounds with any number of alternative sounds. The only stipulation is that the alternative sounds be validated; however, the committee has yet to validate even the recommended sounds.


Clearly, the alarm-system standard needs further refinement before it is ready for public release. According to industry reviewers, it must be made easier to use, it must focus more on general alarm characteristics than on integrated solutions, and it must apply to a broader range of devices. In addition, its recommendations need to be validated through user testing.

When they are complete, however, the guidelines set forth in the standard will be valuable to medical device designers, manufacturers, clinicians, and patients alike. Designers will have set guidelines to follow in developing application-appropriate alarm systems, which in turn will save manufacturers time and money. Clinicians will benefit from alarms that are more informative, enabling them to perform better and enhancing patient care.

Copyright ©2001 Medical Device & Diagnostic Industry

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