Talk:Artificial pancreas

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major rewrite[edit]

While ongoing (citing references, etc), the article was rewritten and updated today. Comments below apply to the older article. mbbradford 04:44, 15 December 2006 (UTC)

If this was just listed under Pancreas, I don't think I would have found it. (unknown, unsigned)

== merging of article from insulin pump ==
Here is the text I propose removing from the insulin pump article and perhaps including in the artificial pancreas artice (some rewriting will be needed). Mbbradford 18:35, 11 November 2006 (UTC)
Currently there are no means to automatically control the insulin delivery from a pump based on real time feedback of blood sugar level sensed by glucose monitoring. The pump user must periodically measure blood glucose with a finger poke, and then program the pump insulin delivery based on a recent blood sugar reading. However emerging technology for continuous blood glucose monitoring makes the real-time data available to control an insulin pump. The concept is to "close the loop" from blood glucose directly to the insulin pump, which could permit the pump to adjust the blood sugar automatically by increasing or decreasing insulin delivery. Several manufacturers of current pumps, including Medtronic (Paradigm, Minimed) and Roche Diagnostics (Disetronic H-Tron and D-Tron) are testing the concept of a closed-loop system.
While the technology is promising, it appears there are unresolved issues with the concept. For example, continuous blood glucose monitoring (CBGM) technology can report very wide variances of blood glucose. Using the non-US measuring system of mmol/l (multiply by 18 to get mg/dL glucose readings used in U.S), a closed-system that detects glucose of say, 15 mmol/l (270mg/dL) might dispense 10u of fast acting insulin. If the patient has an actual glucose level of 6 mmol/l (108 mg/dL) (within the accepted glycaemic range), those 10 units of insulin could very quickly lead to hypoglycemia (low blood sugar, which if not recognised and treated quickly can lead to unconsciousness and perhaps death). There is a lot more research to do on CBGM technology but the first closed-loop systems may be made available for clinical trials by mid-2006.
"Closed loop" insulin pumps--whereby a continuous glucose monitoring system (essentially an implanted glucometer) works in tandem with the insulin pump to constantly monitor, dose, and control blood sugar levels--are currently in the testing phase, and are not in wide distribution. However, some manufacturers are introducing new devices that more fully integrate glucometers and pumps, such as the Minimed Paradigm Real-Time pump, which comprises a glucometer that measures interstitial blood sugar that communicates via RF with the pump to provide a constant (updated every five minutes) real-time readout of blood sugar levels. This is a significant advance over the separate-device approach, in which users test blood sugar on average only four to six times a day. Minimed recommends, however, that users still compare the results of the Real-Time system with an external glucometer to confirm accuracy before dosing. As such, while this is one step closer to an "artificial pancreas," it is not truly a closed-loop system.
The wireless insulin pump most recently approved by the FDA is a wireless insulin pump system co-developed by Medtronic MiniMed and Becton, Dickinson and Company. The system, called the Medtronic MiniMed Paradigm 512 Insulin Pump and Paradigm Link Blood Glucose Monitor, is comprised of a glucose monitor, external insulin pump, and dose calculator that work together to determine the amount of insulin needed.
With the insulin pump, whenever a patient performs a fingerstick, the glucose monitor automatically transmits the results to the pump. The pump, which contains a Bolus Wizard, recommends the proper insulin dosage by calculating the last insulin dosage, the amount of insulin still active in the body, the most recent glucose level, and the amount of carbohydrates to be consumed (input by the patient).
The pump is external and worn like a pager with tubing inserted into subcutaneous tissue. This seamless system is expected to help people manage their disease by fine-tuning the amount of insulin they receive, avoiding calculation errors, and adding convenience.

List of biotech companies[edit]

The following list of research companies studing micro-encalsulation of islet cells was removed from the article as it may encourage link-spamming. I'm temporarily pasting it back in here so that those sources can be reviewed and pertinant data included in the article.

Bio-tech companies working on incapsulated islets and islet sheet technology[edit]

mbbradford 21:02, 29 December 2006 (UTC)

Feedback clarified[edit]

It is understandable why there is confusion regarding feedback being positive or negative in the last three sentences of the first paragraph of section "Background in endocrine physiology" since two of the three sentences refers to a negative feedback system while the third refers to a positive feedback system.

The sentence, "Glucagon causes the liver to release stored glucose back into the bloodstream" refers to a positive feedback system. The more glucagon, the more glucose released (not regulated between two boundaries).

The sentence, "Notice that increased glucagon will increase blood glucose levels in a positive feedback loop" (now changed) could possibly refer to its previous sentence with respect to feedback-type, but that would be out of context. This sentence must be referring to a glucose regulated system in the blood (a negative feedback system), and not referring to the glucagon/glucose/liver system which is a positive feedback system.

The last sentence, "Together, the three endocrine hormones work as a system to control the blood glucose level between high and low boundaries" (now changed) clearly refers to a negative feedback system since the words imply regulation between boundaries.

The confusion is due to a "reference" signal mix up in control theory: if glucagon causes glucose to be released from the liver and into the bloodstream thereby raising the glucose level in the blood, this action causes a positive error with respect to the reference signal (i.e. feedback signal > reference signal) in a negative feed back system thereby causing a regulation action with the release of insulin from the pancreas to decrease the positive error and lower the glucose level in the blood. In this regulatory negative feedback system, there are two reference signals, an upper maximum glucose level and a lower minimum glucose level which makes the system more complex. Henry Delforn (talk) 18:18, 30 July 2009 (UTC)