The respiratory system is rather unusual in the sense that it is autonomous, yet controllable. That means that it functions automatically and allows you to breathe without having to think about it or physically do it on your own.
If you choose to, you can breathe at whatever rate or depth that you desire. You cannot easily control your heart rate, your digestion or your immunity system. But, you can breathe as you desire. With each breath, you exhale CO2 and inhale air, which is 20% oxygen. Since you can only carry a certain amount of oxygen, as it is limited by your hematocrit (red blood cells in the blood), it is difficult to over-oxygenate your body.
It is possible to over-oxygenate, but it requires significant hyperventilation. While trying to accomplish this, there is another exchange that occurs in excess; you release too much CO2.
The result of this hyperventilation is a shift in the pH (acidity) of your blood. It becomes more alkaline. The microbes that pathogenically prey on the human body, have evolved to live in a very narrow range of pH, typically 7.2. If you push the pH out of this range for a long period, they will die off.
Additionally, the enhanced oxygenation of the blood enables the immunity system and produces greater resistance to disease. Interestingly enough, the tingling feeling that you get from this activity also dramatically reduces intense pain.
Hyperventilation will cause light-headedness and should be done for no more than 10 minutes at a time. After performing the hyperventilation, a required rest of 10 minutes is appropriate to allow a return to equilibrium.
Be sure to do this while sitting down. If you are not feeling dizzy, then you are probably not reaching alkalosis. This technique is valuable when combined with the respiratory therapy previously described. It can also be used to deal with any systemic infection. It is extraordinary how quickly a person can recover from something like influenza simply by spending your time lying in bed and hyperventilating.