Hyperbaric oxygen therapy is now well established, but its use is still different. This has created a wide variety of differences in the use of this method, making it unique to each place. The factors that cause the seemingly identical treatment methods to have different effects are: different understanding of a certain disease and treatment ideas, different hyperbaric equipment, different choice of hyperbaric oxygen therapy, different combination of drugs for patients, different choice of dosage, usage and course of each drug, different manufacturers of the same drug, different treatment of problems in hyperbaric oxygen therapy. The effect of different methods of treatment will be different, and the different methods of treatment of problems in the process of drug use will lead to different overall treatment effect, and so on and so forth. Multiplying a few or even a dozen options for each problem mathematically results in a number of millions or even tens of millions or more. These results are the number of treatments that appear to use the same method, but actually yield very different results. For the patient, differences in the treatment of any one of these minor issues can lead to different treatment outcomes. Thus, seemingly the same treatment method, used on a patient through different doctors, yields different actual treatment results.