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October 25, 2016
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Artificially Organic

Much buzz has been going around the diabetes community about the recent announcement of the JDRF/Animas partnership to develop a "first generation artificial pancreas", and rightly so. The ability to eat like a "normal person", to not have to worry about debilitating highs and lows, to be able to sleep without fear of not waking up again... these are things which are, quoth Hamlet, "devoutly to be wish'd". That the road between here and there is not so simple a passage as we might hope, is well-known, and much littered with papers sporting words like "cure", "encapsulation", "transplant", "gene therapy", and -- of course -- "artificial pancreas". This litter is, in itself, cause for consternation every time one of its flags is raised; however, the press release makes it clear that the "first generation" product is likely to be little more than a unified insulin pump and continuous glucose monitor (CGM) with an automatic-suspend feature based on specific CGM-data algorithms.

There is some concern, not without cause, related to the system's reliance on data that is in many ways unreliabile. We've all heard the stories of (or experienced for ourselves) bad sensors and inconsistent readings, whether within a single CGM or between a CGM and a traditional glucometer. Some of us even experience unreliable readings from reliable glucometers (cold hands, anybody?). On the other hand, we've all heard the stories from veterans of diabetes regarding urine testing, hand-sharpening needles, and highly-restricted diets -- and we can see how far diabetes therapeutic technology has come in the past half-century.

As a non-insulin-dependent diabetic, I have the luxury of taking a bit of a sideways angle on the issue -- in this case, that of other "artificial organs" or their counterparts, and long-term therapies.

Probably the most well-known device using the "artificial" moniker is the "artificial heart". Much like insulin pumps, this device started off as something large, external, and temporary -- like the heart-lung machines in today's operating theaters -- and evolved into a variety of devices, including "artificial hearts" that can be used either as a bridge between total heart failure and the receipt of a donor heart, or as end-stage therapy where the patient is not eligible for heart transplant and "left ventricle assist devices" (LVADs) that can delay or eliminate the need for a heart transplant. Separately, artificial pacemakers (used to replace the bioelectrical signals telling the heart when to pump) have evolved from external, spring-wound devices that signalled at a constant pace to dynamic pacemakers that monitor the levels of carbon dioxide in the blood, body temperature, and adrenaline to estimate levels of physical activity, and adjust their rate accordingly. Some modern pacemakers use microprocessors to control the atria and ventricles separately. Finally -- while we still have big, crash-cart defibrillators, technology has improved to the point where many business establishments have automated external defibrillators (AEDs) on-hand for first-responder use in sudden cardiac events, and some heart patients have implantable defibrillators (ICDs).

It's vital to keep in mind that none of the artificial-heart and heart-assist technologies is 100% reliable with every patient, all the time. A dear friend of mine had a number of issues with her ICD firing when it should not have, and not firing when it should have. This sort of misbehavior is a medical emergency whose consequences can be as rapidly fatal as hypoglycemic seizures, and cannot be mitigated with something as (relatively) simple as a glucagon shot.

Other organ functions are also artificially assisted or replaced, although -- with the exception of corneas used in the treatment of cataracts -- we don't tend to use the term "artificial" when referring to them. Dialysis machines are basic artificial kidneys; eyeglasses (and even moreso, contact lenses) are de facto artificial eyes. While limbs are generally not considered organs, bionics research aims at using an amputee's residual neural impulses to drive prosthetics ("artificial limbs") so that they behave as closely as possible to normal human arms, legs, and hands.

The general development path is from large, basic-function machines and devices to smaller, sometimes implantable devices which -- because of improvements in microprocessors and materials technologies -- more-closely replicate the complex responses of the organs and body parts they are designed to assist or replace.

When we boil it down to basics, we think: a heart pumps; a kidney filters; an eye sees. (We don't usually think of the details about how they dynamically respond to stimuli.) A pancreatic islet cell not only has to produce insulin, but it also needs to know when, and how much to produce; it also needs to know when to release the insulin, and when to hold it back. These depend on a number of signals from the brain, the stomach, the liver, and other vital organs. An insulin pump that is as responsive as a modern-day dynamic pacemaker would need to monitor glycogen, leptin, and ghrelin levels, adrenaline and cortisol levels, gastric muscle activity, and a number of factors in addition to current blood glucose levels in order to determine how much insulin to release, when, and when to signal the liver to release more of its glycogen stores. I find it hard to visualize this happening without some sort of surgically-implanted sensor, and possibly a surgically-implanted device with a fill port (possibly based on today's "lap band" technology) and a separate output that releases insulin directly into the bloodstream.

Still -- the original artificial hearts required huge external power supplies and only pumped in one style, at one rate. The Wikipedia entry on "artificial hearts" suggests we may have a fully-implantable (no external power source required) one within five years -- about fifty years after the original prototype external devices. In twenty-five years, insulin pumps have evolved from jet-pack-sized luggables to lightweight cell-phone-sized devices with the ability to program in complex actions and correct imbalances (relatively) on-the-fly. They've come a lot further than the "artificial heart", in half the time. They've come about as far as external pacemakers, in a similar timeframe.

Based on those timelines, it may take another twenty-five to thirty years to come up with a device that will accurately measure -- and respond to -- the range of factors responsible for variations in one's blood glucose levels. Whether or not we decide it -- or the pumps many people with diabetes wear today -- are worthy of the title "artificial pancreas", is another story. For now, development continues -- and if the control algorithms fail, there is medical technology available (insulin and glucagon shots, or in paramedic-mediated emergencies, intravenous insulin and/or glucose) to back it up. That is enough for the more intrepid among us to help test the devices that will help the generations that follow us to live more "normal" lives, diabetes notwithstanding, and enough for the rest of us to cheer them on.

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