A person who requires insulin must walk a tightrope. Blood-glucose concentration can swing dramatically, and it is particularly affected by meals and exercise. If it falls too low, the person may faint; if it rises too high and stays elevated for too long, the person may go into a coma. To avoid repeated episodes of low blood glucose, patients in the past would often run their blood glucose somewhat high, laying themselves open to long-term complications, such as nerve damage, blindness, and heart disease. And patients always had to keep one eye on their blood glucose levels, which they measured many times a day by pricking their fingers for drops of blood. It was easily the most demanding therapy that patients have ever been required to administer to themselves.
No longer: The artificial pancreas is finally at hand. This is a machine that senses any change in blood glucose and directs a pump to administer either more or less insulin, a task that may be compared to the way a thermostat coupled to an HVAC system controls the temperature of a house. All commercial artificial pancreas systems are still “hybrid,” meaning that users are required to estimate the carbohydrates in a meal they’re about to consume and thus assist the system with glucose control. Nevertheless, the artificial pancreas is a triumph of biotechnology.
It is a triumph of hope, as well. We well remember a morning in late December of 2005, when experts in diabetes technology and bioengineering gathered in the Lister Hill Auditorium at the National Institutes of Health in Bethesda, Md. By that point, existing technology enabled people with diabetes to track their blood glucose levels and use those readings to estimate the amount of insulin they needed. The problem was how to remove human intervention from the equation. A distinguished scientist took the podium and explained that biology’s glucose-regulation mechanism was far too complex to be artificially replicated. Boris Kovatchev and his colleagues disagreed, and after 14 years of work they were able to prove the scientist wrong.
It was yet another confirmation of Arthur Clarke’s
First Law: “When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.”
healthy endocrine system, the fasting blood glucose level is around 80 to 100 milligrams per deciliter of blood. The entire blood supply of a typical adult contains 4 or 5 grams of sugar—roughly as much as in the paper packet that restaurants offer with coffee. Consuming carbohydrates, either as pure sugar or as a starch such as bread, causes blood glucose levels to rise. A normally functioning pancreas recognizes the incoming sugar rush and secretes insulin to allow the body’s cells to absorb it so that it can be used as energy or stored for such use later on. This process brings the glucose level back to normal.