W6 Advanced Insulin Delivery (AM) Flashcards
What are the problems with conventional insulin delivery? (7)
- Inconvenience
- Needle phobia / social stigma
- Patient compliance and inaccurate dosing
- Hypoglycaemia risk
- Postprandial (after meal) glucose control
- Injection pain
- Lipodystrophy
Stimuli-responsive insulin delivery
We want a device which can automatically detect
changes in blood glucose and then release insulin.
What does the detector, trigger and releaser do?
Can polymers be used to help develop such a device?
Detector: measures glucose concentration in blood (or other tissue)
Trigger: causes a chemical or physical change in drug delivery system
Releaser: Switches on release of insulin
Then negative feedback loop and cycle repeats
Could be achieved by a physical change in a polymeric material in response to an environment change
Polymer approaches have been explored for insulin delivery with only limited success
Stimuli-responsive insulin delivery: pH-sensitive polymers
When there is a high pH what occurs?
Unionised- polymer contracted
Ionised (charged)- groups repel; expanded structure
Stimuli-responsive insulin delivery
What are the 2 approaches?
- Insulin polymer gels
- Gel-sol transition
Stimuli-responsive insulin delivery
Insulin polymer gels:
How does it work?
What is the chemical reaction formula?
A change in glucose concentration alters the pH as: The enzyme glucose oxidase is included in the polymer formulation
Glucose + O2 + H2O— (glucose oxidase)—- Gluconic acid + H2O2
Stimuli-responsive insulin delivery:
Gel-sol transition
How does it work?
- Small pores in the device are blocked with a polymer gel
Glucose + O2 + H2O— (glucose oxidase)—- Gluconic acid + H2O2 - Open pores now allow insulin to be released from the reservoir
- These polymer approaches are theoretically sound but in practice have not yet been successful * Any local pH changes, i.e. those not caused by glucuronic
acid production, would also lead to insulin release Insulin reservoir - Build-up of H2O2 needs to be addressed
- Other smart approaches have proven more successful
What are Insulin pumps?
What insulin do they release?
Pumps can be broken down into what two categories?
- Insulin pumps are portable programmable devices that deliver insulin directly into the body continually without the patient needing to inject themself
- Subcutaneous needle or cannula delivers the insulin under the skin at the chosen site – continuous subcutaneous insulin infusion (CSII)
- Constant release of (short-acting) basal insulin plus bolus doses at mealtimes
- Tethered pump
- Patch (tubeless) pump
A Variety of different brands of tethered and patch pumps are available in the UK
What are some examples?
- Tethered pumps
− Medtronic 640G, 670G and 780G
− Tandem t:slim
− Dana R
− myLife YpsoPump
− Accu-Chek Spirit Combo - Patch pumps:
− Insulet OmniPod Dash
− Medtrum Touchcare Nano
These devices are available on the NHS but not all patients may be eligible. They can also be bought privately
Tethered insulin pumps
What are the features? (4)
Pump- Battery powered device containing the insulin reservoir, pumping mechanism, control buttons and/or screen to program insulin delivery
Tubing- Flexible plastic tube connects
the insulin reservoir to an “infusion set”
Cartridge and Plunger, Piston rod and end plate
Infusion sets- The infusion set attaches to the skin with an adhesive patch. The set contains a needle/cannula that delivers
insulin subcutaneously. Often used around the abdomen, but can be placed on the upper arms, thighs etc
Infusion sets are typically changed every 2-3 days
Patch (tubeless) pumps
What are the features?
The most commonly available patch pump in the UK is the Insulet Omnipod Dash
* Patient manually fills a new pod with insulin using a syringe
* Pod can be placed at most sites around the body where you would normally inject insulin
* Cannula inserts semi-automatically once pod has been attached to the skin
* Wirelessly connects to a personal diabetes manager (PDM)
* IPX8 waterproof rating for the pod (not the PDM)
What if a pump malfunctions?
What are signs of a pump malfunction?
What to do next??
Signs of pump malfunction:
− High blood glucose symptoms, e.g. thirst, tiredness, frequent urination
− Ketones in urine
* Stop the pump and administer correction (bolus) dose from backup pen
* Look for air bubbles, change cannula/ infusion set/ tubing
* Continue with insulin from pen if device changes do not resolve issue
* Check glucose/ ketones regularly, i.e. every 1-2 hours – do not go to bed until levels have returned to normal
* Contact healthcare professional and/or pump manufacturer
Continuous glucose monitoring (CGM)
is an alternative to what?
What are the 2 types?
Finger prick testing
− Real-time (rtCGM)
− Intermittently scanned (isCGM) or “flash” CGM
- Newer techniques and devices are a big
improvement on the GlucoWatch® - Disposable sensor with a 0.4 mm filament is inserted 5 mm under the skin
What does the traditional method of monitoring BG levels?
What is required? (4)
Why are some people averse to this?
- Traditionally patients have monitored their BG levels by finger-prick
methods - Requires: (1) meter + (2) test strips + (3) finger-prick device + (4) lancet
- Some patients averse to regular finger-prick testing and BG levels can fluctuate considerably between tests
Properties of isCGM (flash)
e.g. Freestyle Libre
- BG levels only show when you scan the sensor
- Not used alongside insulin pumps
- Sensor location: back of upper arm
- 4 years old and above
Features of rtCGM?
- BG levels continuously updated on smartphone/device
- More compatible with insulin pumps
- Sensor location: more options
- 2 years old and above
