Continuing the discussion from Dexcom Users Direction Arrows:
A recent discussion about the meaning and use of the Dexcom arrows versus the dots suggests that this visual indicator could be improved.
I used to work as a technician in an avionics shop for a major commercial airline. Many of the instruments and cockpit displays integrated a long history of aviation evolution. Many changes to features in cockpit displays were informed by actual airplane crashes! The displays built in the whole field of ergonomics because at 30,000 feet high, life literally hangs in the balance.
The various instruments and displays must communicate a strong visual presentation dense with vital information. They pilot cannot visually fixate on one display at the expense of focusing on myriad other systems and what appears outside his/her cockpit window. Situational awareness suffers too much complexity and confusion.
Why re-invent the wheel?
Therefore the various instruments and displays that my shop serviced were well honed devices that benefitted from decades of use. Their visual presentation was concise, clear, intuitive, and right to the point.
One of the instruments that my shop serviced was the Vertical Speed Indicator or VSI. This analog indicator consisted of a pointer mounted on a round display that deflected up or down to immediately indicate whether the aircraft was gaining, losing, or maintaining altitude.
A flight level indication was a pointer holding steady at the 9:00 o’clock or pointing left condition. If the pointer moved clockwise, or up, it meant the aircraft was climbing. If the pointer moved counter-clockwise or down it meant the aircraft was descending. One quick look and the pilot could immediately learn this important flight info.
Here’s a visual of what this instrument looks like:
It’s calibrated in 100’s of feet per minute. Intuitive, simple, and fast to read.
Could medical device builders learn from commercial aviation?
I suggest that the Dexcom (and other mfgr’s.) could borrow this design concept and build into our CGM displays a much better way to represent the speed of blood glucose movement up or down. The current system is misleading. The linked discussion shows the confusion it sows relating to the all too frequent disagreement between the arrow and the dots.
When the Dexcom arrow is level, it only means that the blood glucose levels are not moving up or down by more than 1 mg/dl for every minute. In other words a level arrow can mean anything from truly level blood glucose to one moving up or down 15 mg/dl every 15 minutes. The latter condition is anything but level in my book!
CGM manufacturers could easily incorporate the intuitive smarts built into an aircraft VSI. Now I know that there is a about a 15 minute lag in the interstitial indication of blood glucose when compared to a fingerstick reading. We’ll have to live with that reality for the time being. But the current situation could be markedly improved by building in a presentation informed by commercial aircraft VSI display.
A CGM display that informs instead of confuses
The up or down markings on an analogous CGM display could mark off +1, +2, +5 and +10mg/dl per minute as well as the -1. -2, -5, and -10 mg/dl per minute.
I also know the the We Are Not Waiting movement has been able to use the Dexcom “raw data” for their benefit. Perhaps this raw data is more frequently available than every 5 minutes. That would enable CGM VSI to track more closely and update more frequently.
This doesn’t seem like a complicated upgrade to the sometimes misleading arrow system and it communicates actionable info to the brain of the person with diabetes. And it may help pierce the confusion that the fog of high and low blood sugar that impair us sometimes.
Does anyone else think this is a good idea?