Finding the chase and cutting to it

This has been inspired by https://www.sciencedirect.com/science/article/pii/S2468067222001201 .

Having funded a pump myself, I appreciate that the pump itself is an expensive piece of kit, but that isn’t where the costs lie. Let me take you through this.

Examination of cost of buying and running a pump.

Item	Frequency of payment	Cost over life time.
Pump	1xfour years	£3,350
Cartridges	2 boxes a month, so 10 a year @ £32.25 a go for the four years.	£1,290
Infusion sets	2 boxes a month, so 11 a year @ 89.90 a go for the four years	£3,955.60
Grand total	Prices during 2020. This is almost certainly out of date.	£8,595.60

What if we do something different? Take the open source design and gear it towards something that costs less to get going and less to keep running. The trick is the cartridge cost, I feel. If we reuse a mechanism that already existing, preloaded insulin pen cartridges, all we need to do is provide an adapter, which should be a much lower cost.

Item	Frequency of payment	Cost over life time.
Pump	1xfour years	£100
Adapter	2 boxes a month, so 10 a year @ £10 a go for the four years.	£100
Infusion sets	2 boxes a month, so 11 a year @ 89.90 a go for the four years	£3,955.60
Grand total		£4,155.60

Which is a big difference! The clever thing here is the removal of the cartridge in the design of the open pump source pump. By reusing insulin pen cartridges, we just need an adapter, literally a needle piercing the cartridge and providing an anchor point for the tubing and cannula.

Pen cartridges are available for Lispro (300iu for Admelog, Humalog and Lyumjev), Fiasp (300iu) (a modified aspart), Novorapid (300iu) (aspart), Apidra (300iu) (glulisine).

I’m also keen to swap the mini-USB for a USB C connector. I’m looking to build an app that allows today’s basal to be preloaded through that interface. I think we could use that port to recharge the battery too, which would strengthen the case construction.

Why not use bluetooth for the communication?

Good question, for two reasons: bluetooth is hard to secure, it can be done but it is a broadcast protocol; secondly, I want something that isn’t going to date too quickly. USB C looks good from both points of view. Cables are cheap and it is a common protocol.

Are you allowed to do this?

It’s a good question. I don’t know. Even if I did, it would need testing and refining. One of the big issues with pump therapy is that you can do more damage than good.

So it needs careful examination.