Continuing our Aviation Concepts for Emergency Medicine and EMS series, Dr. Joshua Stilley introduces the aviation concept of the iceberg effect and explores how uncovering one problem should prompt the search for the larger, hidden issues beneath it – in the cockpit and at the bedside.
Article by Joshua Stilley, MD, FACEP, FAEMS; Medical Director, University of Missouri Ambulance
Edited by Michael DeFilippo, DO, FAAEM, Editor-in-Chief, NAEMSP Blog
In emergency medicine and EMS, we use many cognitive tools to enhance decision-making. One of the most prominent frameworks, Crew Resource Management (CRM), has been adopted from the aviation industry. However, there are numerous other mental models that pilots utilize to safely conduct flights, which can also apply to emergency care. In this series, we will explore fundamental aviation principles and discuss how they apply to healthcare, using specific case examples.
While it probably didn’t originate in aviation (airplane crashes into icebergs are quite rare), it’s easy to see how the iceberg principle applies both to aviation and healthcare. It is based on the idea that only a small portion of an iceberg is visible above the surface, while the majority remains hidden below. In this context, uncovering one problem suggests that there are often larger or more complex underlying issues that have yet to be discovered.
The iceberg effect is essentially the opposite of the satisfaction of search phenomenon. In healthcare, satisfaction of search occurs when one problem is identified, and as a result, no further problems are considered. For example, a clinician might see a fracture on an X-ray and assume that’s the only issue, thereby missing an additional fracture also visible on the image. The iceberg effect, however, encourages the opposite mindset – once a problem is found, the observer should actively search for additional, hidden issues. A teaching phrase I like to use in this context is:
“What’s the most commonly missed fracture? The second one.”
Aviation Application: Fuel Status
The iceberg effect is particularly relevant to aviation, where it can apply to situations like fuel status – a critical factor in aircraft operations and a frequent cause of aviation accidents. An aircraft may have more than one way to gauge fuel levels including visual sight gauges and mechanical or electrical fuel level indicators. However, aviation fuel gauges are notoriously unreliable.
A common saying is that “the fuel gauge is accurate twice: at full and empty. Anything in between is just a guess.”
Some pilots may dismiss unreliable fuel gauges and instead rely on other means to estimate fuel. Other methods of identifying fuel levels include fuel totalizers that measure how much fuel flows into the engine but not the fuel level itself, or burn rate calculations where the average fuel flow per hour and tank capacity is used to estimate fuel remaining. However, following the iceberg effect, a low fuel reading should be a red flag, regardless of other data. Even if a pilot has calculated that there should be plenty of fuel, that one piece of negative information (the low gauge reading) should prompt further investigation. One small issue may point to larger, undiscovered problems. A missing fuel cap may result in a leak of fuel, and fuel burn calculations or fuel totalizers will not pick up on this abnormality.
Aviation Example: My Own Experience
An example from my own flying experience highlights the iceberg effect. My family and I were departing from our local airport in our club’s Cessna 182. This aircraft has retractable landing gear and had just come out of its annual inspection. I assumed that everything was in good working order after the test flight, so we were set for our trip to Oshkosh – a trip I had been eagerly anticipating. However, during climb-out, it became apparent that the gear warning horn hadn’t been set correctly. While this had no significant impact on flight safety, applying the iceberg principle made me pause. Since one problem had surfaced, I assumed there could be more underlying issues that hadn’t yet been identified. The prudent course of action was to land and drive to Oshkosh instead of flying. While an eight-hour drive wasn’t as fun, I didn’t want to continue flying an aircraft that I didn’t fully trust.
Healthcare Application: Oxygen Saturation
In healthcare, the iceberg effect can be easily applied to situations involving oxygen saturation. How often have you or a colleague repeatedly tried to get a “better” oxygen saturation reading when the number on the monitor looks concerning? While the pulse oximeter reading can be contextualized, a poor reading is often all the information needed to recognize that the patient isn’t adequately oxygenating, whether due to poor perfusion, hypothermia, or equipment malfunction. Instead of working hard to fix the number, we should apply the iceberg principle – acknowledge the poor reading and act quickly to correct the underlying issue.
Another Healthcare Example: Perfusion
This principle can also be applied to perfusion status. We have many direct markers of perfusion, such as mental status and capillary refill, as well as surrogate markers like blood pressure. However, I often see clinicians focus on the best piece of information, rather than the worst. The iceberg effect suggests that if we find one problem (e.g., poor capillary refill or altered mental status), we should assume there may be more issues, even if some indicators – like blood pressure – appear normal. Relying on a single normal value while ignoring other abnormal signs can be detrimental to patient care.
Fixating on a normal number, despite objective or contradictory data, so that we can continue our pre-determined course of care, can bring significant detriment to the patient. Pivoting away because of negative information to a different plan of action can have significant impact on our patient’s outcomes. How many times have you had a lift-assist patient say they are fine, on assessment they look not too bad, but have significantly abnormal vital signs? Which one of these markers is the one to bank off of?
Conclusion
The iceberg effect in healthcare teaches us to remain cautious and curious. Once a problem is identified, we should assume there are additional, hidden issues. Just like in aviation, where one minor malfunction can be the tip of the iceberg, in healthcare, one abnormal reading could point to larger, more dangerous conditions. By using this principle, we can improve our vigilance and deliver safer, more effective care to our patients.
