Then and Now: This Month in Endocrine History
Submitted by Evan Graber, DO
In 1963, Arnold H. Kadish reported on the use of a “servomechanism for glucose monitoring and control,” the first closed-loop system. A patient with known diabetes had IV catheters placed for blood to infuse to an “Autoanalyzer” and to receive intervention. The patient had a glucose above 150 mg/dL, which activated a syringe pump to deliver insulin. A recorder displayed the continuous glucose values after a 7 minute lag time and the insulin infusion automatically stopped when the glucose value dropped under 150 mg/dL. In a volunteer without diabetes who was given insulin, when the blood glucose dropped under 50 mg/dL, a syringe pump with glucagon was activated. This pump automatically stopped when the glucose was over 50 mg/dL. Unfortunately, the entire setup was the size of a kitchen table and was prohibitively expensive (the moderator of the meeting quipped, “The autoanalyzers cost only $10,000 so I don’t see what people are waiting for”).
What were large, expensive, and invasive machines now fit into a patient’s pocket or are worn directly on the body. Some are no larger than a nickel and nothing has to be placed intravenously. The interplay of small continuous glucose monitors and insulin pumps has improved glucose control and quality of life for countless people with diabetes.