had recently finished inducing anesthesia for a complicated patient while working with a new resident. During the anesthetic, the insightful resident asked me a series of questions about the monitor we were using, our airway management, the ultrasound device we used to facilitate central venous access and the intravenous infusion pump.

“Why did the patient monitor indicate significant S-T segment depression prior to induction of anesthesia when the patient reported no symptoms?” I explained that the monitor had failed to select the proper points for S-T analysis due to the influence of a prior myocardial infarction on the baseline electrocardiogram. As a result, the isoelectric point was initially on the Q wave in lead two. Pressing a series of buttons, I showed the resident how to navigate to the S-T analysis window of the device and manually set up the S-T analysis properly. The resident remarked at how complicated the process seemed and was not certain she could reproduce the same steps on her own.

Since the patient actually did have cardiac disease and was on beta-blockers, she then asked, “Why were the heart rate (HR) alarms set for < 50 and > 150?” I explained that the default alarms for HR and blood pressure were configured for extreme deviations and that they were indeed not appropriate for this patient in whom ischemia could develop with more modest changes in hemodynamics. Again, making changes to the alarm limits required complex navigation in the monitor that I was sure the resident would forget.

During intubation the apnea alarm sounded, and the resident turned to look at the monitor, losing focus on the task at hand. When told to keep her eye on the ball, she asked, “Did the monitor always blare its alarm for apnea in the middle of laryngoscopy and intubation?” I acknowledged that the alarm in this case was a nuisance as we were acutely aware of the patient’s apnea while attempting to intubate. That apnea alarm would be useful during the maintenance phase of anesthesia, but the monitor is unable to relate alarms to clinical context. The teaching point was not to be distracted by a nuisance alarm at some occurrences and to pay attention to the alarm at other times. Although the resident understood the concept, it was clear that she would need experience to decide when to ignore alarms and when to take them seriously.

Later, during placement of a central venous catheter in the jugular vein, I demonstrated the use of ultrasound to define the anatomy and guide venous access. During the procedure, I had to stop her from inserting the needle too deeply while she was engrossed in viewing the ultrasound image despite being unable to see the needle tip (a common mistake among novices).¹ The resident had placed many central lines during her internship, and she queried, “Why use an ultrasound device for placing a central venous line? It seems to be more trouble than it is worth.” While I am convinced that this technology eliminates the uncertainty associated with anatomic variability seen in patients, I admitted that the learning curve was a barrier to broad acceptance by many anesthesiologists.

When setting up a phenylephrine infusion to manage hypotension, the resident asked, “Did the fact that the infusion pump took several minutes to set up ever pose a problem in an emergency?” I explained that this programming complexity was part of the reason our department still supported setting up selected infusions in advance on high-risk patients, even though the practice resulted in waste of drug and tubing.

While in my office at the end of the day, I began to daydream about the future. The year was 2050. Miraculously I was still alive and practicing anesthesiology. I was again working with a resident and explaining how our tools and technology had advanced in the last 50 years. First I cited the sensor advances that now allowed oxygenation, ventilation and perfusion parameters to be measured continuously and noninvasively. Between the years 2000 and 2020, devices became miniaturized and wireless. This improved the ergonomics of our workspace dramatically by reducing clutter and tangles and simply creating more space.

As my daydream continued, I lectured the resident on how the poor human-user interfaces of the past undermined optimal anesthesia care and how improvements in usability* had improved patient outcomes. I noted that by 2050, advances in human-factors engineering were used to guide the design of our monitors, drug delivery systems and even our airway management and intravenous access tools. In this ongoing dream, I tell the resident that over the last 50 years, the usability of our tools and technology had improved dramatically, and I outlined the major changes that had occurred.

Change 1: Clinical problems now drive the design of technological solutions. Unfortunately, in the past, owners of new technologies would look for a medical problem to solve and there was a fascination with “high tech.” Often the most successful solution to a problem is relatively “low tech.” For example active warming units that use hot air and a disposable blanket are effective for reducing perioperative hypothermia, but they were a “low tech” solution in the 1990s when they were introduced (basically a hair dryer and an air mattress). In contrast, during the same time frame, continuous intra-arterial blood gas monitoring using “high tech” sensor technology was introduced. This technology failed to be widely accepted since it did not address a significant need that was not already being met by intermittent measurement of blood gases.

Change 2: Usability became a priority in the anesthesiology and perioperative domain. High-consequence, low-error tolerance domains (like that of perioperative care) came to realize that high-reliability performance can only be accomplished by reducing complexity. Human factors science was championed as the applied science dedicated to optimizing performance of complex human-machine work systems. Medical device manufacturers took lessons from other industries, realizing that good human-factors design could be protected by patent and used to both add clinical value and differentiate their products in the marketplace. I explained to the resident, as an example, that a leading $20 billion pharmaceutical company that made medical devices only employed one human-factors specialist in the year 2000 (most companies employed none and/or used consultants sporadically). The same year, the NASA Ames Research Center in Palo Alto, California, employed more than 100 human-factors specialists dedicated to designing the human-machine environment for aviation and the space program.

Change 3: Basic human-factors principles were written into the medical device standards.^2,3 All devices used in the operating room (O.R.) were required to have intuitive labeling and be visible within typical working distances for an individual with 20/40 visual acuity. All control surfaces, knobs, buttons, etc., were required to be back-lit such that they could be easily seen and used in a darkened room. The resident was surprised when I stated that we used to keep flashlights and lamps in the O.R. so that we could utilize our equipment during procedures when the room was darkened. Automation was now used selectively and only when the automation provided a clear advantage. Smart intravenous pumps in the future of my dream now used bar coding to connect to a drug library and thus simplified setting up controlled infusions of potent medications.

Change 4: Advanced physiological information displays had become the standard. I explained to the resident that we used to suffer from the problem of data overload but information underload in the practice of anesthesiology. Advanced displays now organized raw data so that important information could be visualized in the proper context.⁴ Better information ultimately had a major impact on the quality of decision making by anesthesiologists faced with managing complex events in the O.R. Specifically, advanced monitors organized data to amplify boundary violations, temporal changes and relationships with other patterns. We can now identify events quite easily by viewing our displays rather than having to assimilate raw data and see the pattern in our “mind’s eye.”

Change 5: Devices evolved to become smarter and more situationally aware.⁵ Alarm behavior and alerting were rarely a nuisance. Anesthesiologists now spoke to the monitor to inform it when intubating so that the monitor “knew” not to worry about an interval of apnea. It also knew, however, when to alert the anesthesiologist having intubation difficulty as to when the oxygen saturation was starting to decrease so that the anesthesiologist could move to a contingency plan appropriately. Ultimately we human members of the anesthesiology team came to view our monitors as cooperative teammates rather than distractions.

Suddenly I am startled from my day dream and am back in the year 2004. I was thankful for the technologies I had used all day to accomplish my work but also cognizant of the limitations imposed by suboptimal human factors design. Overcoming those limitations will be the challenge to human factors engineers. Ever an optimist, I look forward to the changes ahead.

* Definition of usability: Novices can routinely acquire expert performance with the new tool or technology with minimal practice and maintain expert performance with minimal reinforcement.

References:

1. Sites B, Cravero J, Gallagher J, Lundberg J, Blike G. The learning curve associated with a simulated ultrasound-guided interventional task by inexperienced anesthesia residents. Regional Anesthesia and Pain Medicine. (in press).

2. Norman DA. The Psychology of Everyday Things. New York, NY: Basic Books; 1988.

3. Sanders MS, McCormick EJ, eds. Human Factors in Engineering and Design. 7th ed. McGraw Hill, Inc; 1993.

4. Tufte E. TheVisual Display of Quantitative Information. Cheshire, CT: Graphics Press; 1983.

5. Gershenfeld N. When Things Start to Think. New York, NY: Henry Holt and Co; 1999.
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George T. Blike, M.D., is Associate Professor of Anesthesiology, Director of Dartmouth Medical Interface Laboratory, Dartmouth College of Medicine, and Medical Director of Patient Safety for Dartmouth Hitchcock Medical Center, Lebanon, New Hampshire.