$40 ozone generators on eBay don't work for therapeutic purposes. I have one. The key to ozone therapy is combining 100% oxygen. Ozone generators create a single molecule of oxygen, it's what they do, combined with oxygen creates O3 or 3 combined oxygen molecules. When combined with pure 100% oxygen the percentage output of ozone gas is still very low, something like 2-3%, low but still effective. So if you combined it with ambient air which is 20% oxygen you would get an output concentration of ozone of .4% to .6% or even less because it's very unstable, so it's just not an effective therapeutic dose. The cheap eBay generators might in fact make good ozone, I don't know, but they don't provide the facility or connections to combine it with 100% oxygen, they're just to low a concentration and not set up for therapeutic purposes. Ozone for therapy purposes are measured in gamma concentrations and you can find them in concentrations of 50-70 gamma but I've seen them higher. I use 30-40 gamma for most of my home therapy purposes. I would be careful anyone trying to suggest that these cheaper ozone generators do anything other than provide a disinfectant effect, they are not for therapeutic use. This is very well documented in every reference to the therapeutic use of ozone. You need to study air embolisms in context to pure oxygen combined with ozone, it's not the same as you have displayed above. Nitrogen is the main problem when injecting ambient air into the vein, which is not the case here. Rectal insufflations are a very popular method of exposing the body to hundreds of different therapies and has used for hundreds of years. Good for you for finding some obscure study not pertaining to human beings. Rectal insufflations are probably the most popular method for people using home ozone therapy. It's easy and safe to administer. I've read dozens of books and articles, I work with 2 GPs who have studied ozone in Europe in med school and treat patients daily. I belong to several closed Facebook groups with thousands of other people who have read dozens of books and articles and use ozone therapy regularly at home and in clinics. Using ozone generators that don't combine with 100% oxygen for therapy purposes is unanimously panned. I use various forums like these to find new ideas to diagnose and tread problems I've had for 15 years where the traditional medical and science establishment have failed me. I find them invaluable and I am very thankful. But not every therapy works for ever person in the same manner. One mans bread is another man's poison. So I caution people to do their own research, weigh their own options, have an open mind, turn yourself into your own research scientist, be your own Dr, and you can do it because they are only humans with a curious mind. Don't seek answers in science that are 100% correct, there are always variables, it's about a risk to reward ratio, a percentage of success. If it has a better than 50% chance of working, but the risk is lower and acceptable, then it's worth a try. Be cautious, but don't wait for others to decide for you. For every scientific study you will find another to contradict, that's normal, because in science and health is not 100%, nothing is, it's based probabilities of success and percentages. Listen to people who have found something(s) that works, then bring it into your situation, all the complexities that are you, decide for yourself, self experiment, take risks but make sure they are reasonable. Don't listen to people who just pick things apart, that's easy, lazy, we can pick anything apart because nothing in science is 100% absolute. Look for forum posts where people ask why or how things work, look for fellow learners, look for posts that progress the conversation instead of contradicting it, that's just lazy and counter productive. Help yourself and help others, it's a cycle that works. Good Luck in your health journey. I hope this helps.