Try drinking more water, with a pinch of salt for every liter you drink, and see if your breathing gets easier.
How much Oxypowder did you take? Were you having liquid bowel movements?
It is important to drink enough water when you take Oxypowder (or any other bowel cleansers) to keep your body replenished as you move things out.
I use Oxypowder for 2-3 days before a Liver Flush and then for 2-3 days after the flush to get all the stones out. Oxypowder releases oxygen into the intestines. It helps you digest your food and also pulls water into the intestines from the body. This is how it cleans. In general, you need to drink 6-8 glasses of pure filtered water every day. When you take Oxypowder, you need to drink a bit more.
I'm surprised at your Naturopath's statements about the diaphragm and digestive enzymes.