SIMULATION OF INSULIN PUMP

PROFESSOR

Prof. Dr. Mr. Matthias Wagner -Chairman, High Integrity

Systems(Masters)

SIMULATION OF INSULIN PUMP

TEAM PARTNERS:

B.RAVI KUMAR MOHAMMED SARFARAZ KHAN (MSK) RISHU SETH SOHAM KULKARNI MOHAMMAD TARIQUE ABDULLAH

OBJECTIVES•What is diabetes?•Short and long term consequences of diabetes

What is Diabetes? no insulin production insufficient insulin production resistance to insulin’s effects

No insulin to move glucose from blood into cells: high blood glucose means:

h fuel loss. cells starveh short and long-term

complications

DIABETES• People with diabetes cannot make their own insulin, a hormone that is normally secreted by the pancreas. Insulin is essential to metabolise sugar and hence generate energy• Currently most diabetics inject insulin 2 or more times per day, with the dose injected based on readings of their blood sugar level• However, this results in artificial blood sugar fluctuations as it does not reflect the on-demand insulin production of the pancreas

DIABETES IS MANAGED,BUT IT DOES NOT GO AWAY.

GOAL:To maintain target blood

glucose

SUGAR LEVELS• Unsafe

A very low level of sugar (arbitrarily, we will call this 3 units) is dangerous and can result in hypoglaecemia which can result in a diabetic coma and ultimately death.

• SafeBetween 3 units and about 7 units, the levels of sugar are ‘safe’ and are comparable to those in people without diabetes. This is the ideal band.

• Undesirable Above 7 units of insulin is undesirable but high levels are not dangerous in the short-term. Continuous high-levels however can result in long-term side-effects.

PRESCRIBED SOLUTION

• Simulation of an Automated Insulation Pump which would check glucose levels at regular intervals and inject the required insulin

SAFETY VALIDATION•Design validation

Checking the design to ensure that hazards do not arise or that they can be handled without causing an accident.

•Code validationTesting the system to check the conformance of the code to its specification and to check that the code is a true implementation of the design.

•Run-time validationDesigning safety checks while the system is in operation to ensure that it does not reach an unsafe state.

SYSTEM TESTING• System testing of the software has to rely on simulators for the sensor and the insulin delivery components.• Test for normal operation using an operational profile. Can be constructed using data gathered from existing diabetics• Testing has to include situations where rate of change of glucose is very fast and very slowTest for exceptions using the simulator

A PERSONAL INSULIN PUMP

• A personal insulin pump is an external device that mimics the function of the pancreas• It uses an embedded sensor to measure the blood sugar level at periodic intervals and then injects insulin to maintain the blood sugar at a ‘normal’ level.

NICE Guidance No.57

“Insulin pump therapy is considered as a treatment option for people with Type1 diabetes for whom multiple dose insulin therapy has failed and who have the commitment and competence to use CSII therapy effectively”

Feb 2003

CRITICAL SYSTEM ATTRIBUTES

• Availability-It is important that the system should be available to deliver insulin when required

• Reliability-It is important that the system performs reliably and delivers the correct amount of insulin to compensate for the current level of blood sugar

• Safety-A system failure that resulted in excessive doses of insulin being delivered could threaten the life of the user

INSULIN DELIVERY SYSTEM

• Data flow model of software-controlled insulin pump

Insulinrequirementcomputation

Blood sugaranalysis

Blood sugarsensor

Insulindelivery

controller

Insulinpump

Blood

Bloodparameters

Blood sugarlevel

Insulin

Pump controlcommands Insulin

requirement

CONCEPT OF OPERATION

• Using readings from the embedded sensor, the system automatically measures the level of glucose in the sufferer’s body• Consecutive readings are compared and, if they indicate that the level of glucose is rising (see next slide) then insulin is injected to counteract this rise• The ideal situation is a consistent level of sugar that is within some ‘safe’ band

Injection scenarios

Level of sugar is increasing Reading in unsafe band

No injection. Reading in safe band

Inject only if the rate of increase is constant or increasing. If constant, inject standard amount; if increasing, compute amount based on increase.

Reading in unsafe band Inject constant amount if rate of increase is

constant or decreasing. Inject computed amount if rate of increase is

increasing

Exact dosing of insulin

Basal rates changed half hourly Adjusted in 0.05 unit increments Temporary basal feature Boluses calculated on BG level, CHO, insulin

sensitivity, active insulin Boluses -immediate or protracted Can be adjusted in 0.1unit increments

Pumps

Provide adjustable, constant, SQ insulin infusion via a small plastic cannula which is left in place under the skin for several days.

Are a pager-sized device which is worn on the outside of the body

Insulin delivery system

Safe state is a shutdown state where no insulin is delivered If hazard arises,shutting down the system will prevent

an accident Software may be included to detect and prevent

hazards such as power failure Consider only hazards arising from software

failure Arithmetic error The insulin dose is computed

incorrectly because of some failure of the computer arithmetic

Algorithmic error The dose computation algorithm is incorrect

Insulin system hazards

insulin overdose or underdose (biological) power failure (electrical) machine interferes electrically with other

medical equipment such as a heart pacemaker (electrical)

parts of machine break off in patient’s body(physical)

infection caused by introduction of machine (biol.)

allergic reaction to the materials or insulin used in the machine (biol).

Safety assertions

Predicates included in the program indicating conditions which should hold at that point.

May be based on pre-computed limits e.g. number of insulin pump increments in maximum dose.

Used in formal program inspections or may be pre-processed into safety checks that are executed when the system is in operation.

Safety proofs

Safety proofs are intended to show that the system cannot reach in unsafe state

Weaker than correctness proofs which must show that the system code conforms to its specification

Generally based on proof by contradiction Assume that an unsafe state can be reached Show that this is contradicted by the program

code

Insulin Infusion Pumps

Fairly recent technology Generally fairly easy to use Requires close patient involvement More thinking and monitoring than insulin

by syringe 300,000 users worldwide

Types of Pumps

Open loop: user gathers sugar data and adjusts flow rates for activity, diet, other changes in sugar

Closed loop: the device checks sugar and adjusts insulin infusion

Patients Suited for Pump:

Difficult to control diabetes Active lifestyle/no time for injections Committed to tight glucose control Able to recognize and manage problems

with device Willing to monitor sugars closely and

adjust insulin and diet

Symptoms of a problem:

Blood sugar level is higher than it should be, for no apparent reason.

Failure of sugar to respond when bolus dose given

Problems with Infusion Pumps

Out of insulin? Is the pump leaking? Is the connection between the tubing and

the pump cartridge tight? Is the hub connection cracked? Can you smell insulin anywhere? (hint:

Insulin smells like Band Aids) Can you see insulin drip from the end of

the infusion set if you disconnect and do a bolus?

Infusion Site Problems:

Lack of problem with device. Tissue abnormality

Redness/pain/heat Hard tissue/scarring Kinked cannula Old site Improper depth/too near muscle/wrong angle

Air in line Tube disconnected

Pumps detect:

Computer malfunction Dead battery

Pumps don’t detect:

Disconnection Air in line Infection Leaks Abnormal tissue sites

REFERENCES

http://en.wikipedia.org/wiki/Blood_sugar http://en.wikipedia.org/wiki/Blood_sugar_

regulation http://www.abbottdiabetescare.com.au/di

abets-faq-measure-units.php http://scienceray.com/biology/human-biol

ogy/regulation-of-glucose-by-insulin/ http://www.en.wikipedia.org/wiki/insulin_

pump http://professional.diabetes.org/Abstracts

_Display.aspx?TYP=1&CID=70361 http://www.ncbi.nim.nih.gov/pubmed/196

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