I wasn't too sure how they were generating the carbon dioxide with this device to allow the Bohr effect. It doesn't explicitly say in any of the literature how they do this, so I thought that perhaps the device filtered air to separate out the carbon dioxide?
Now I have used this product and read through the ingredients it's quite clear that the device itself is only there to produce vibration, the CO2 comes from a chemical reaction between the capsule and the gel.
The capsule is almost wholly made of sodium bicarbonate which is compacted into a capsule shape. This reacts with the water of the gel to produce sodium carbonate (often used in toothpaste to create the 'foam'), water, and carbon dioxide. So the white bubbles/foaming that you see is largely coming from the sodium carbonate not the carbon dioxide, but it does show you that the chemical reaction is taking place and thus carbon dioxide is also being produced.
The effect on the skin is nice, however considering the mechanism of the product I would say it is quite expensive for a vibrating pod and some sodium bicarbonate, I would recommend purchasing this when it is on sale.
Considering the mechanism of the product, I would say that you could keep the capsule and re use it for another treatment as long as you pat it dry to stop the decomposition of the sodium bicarbonate. And I don't see why you couldn't use a different skin-friendly gel of your choice, as it is the water in the gel that the capsule is reacting…