The short answer to that question is yes.  Let us explore what happens when we breathe 100% oxygen and why it can be dangerous or even fatal.

First let us look at what usually happens in the lungs with the 21% oxygen that we breathe.  The lungs are a set of tubes and tubules that end in little sacs called alveoli.  How things work tells us to “picture a series of straws with bubbles on the end.”  The bubbles are where the oxygen/carbon dioxide exchange takes place.  The alveoli are surrounded by many little blood vessels that are only one cell thick.  This very thin membrane allows oxygen, nitrogen, and carbon dioxide to pass through the membrane.  This action is called diffusion.  Diffusion is regulated by something called osmotic pressure.  For an oversimplified look at this regulator, we can say that the molecules of oxygen, nitrogen and carbon dioxide will move from where there is more of the molecule to where there is less of the molecule.

When we breathe in the air flows into the alveoli and because there is less oxygen in the blood, the oxygen flows into the blood and because the carbon dioxide is higher in the blood it will flow into the alveoli and be exhaled when we breathe out.  Remember that this is oversimplified but does represent what happens in our lungs.

It would seem then that the higher the % of oxygen in the alveoli the better, but in experiments with guinea pigs in 100% oxygen environment some very adverse conditions presented.  Among those adverse conditions is that the lungs began to fill with fluid that lowered the ability of the alveoli to exchange oxygen by 17%.  The pulmonary capillaries (tiny blood vessels) become damaged as well.  Mucous plugs form and many alveoli collapse because they cannot take in more oxygen.

Mucous production is the expected outcome of damage or irritation to the lungs.  People with lung disease often have mucous production which makes it difficult for the oxygen exchange to take place and the person becomes short of breath.  This mucous production is believed to be the result of inflammation due to irritation.

An individual who is exposed to 100% oxygen over a period of time can result in oxygen poisoning.  Remember that we discussed why hydrogen peroxide is antiseptic.  That antiseptic ability is due to the production of pure oxygen by the hydrogen peroxide.

This is not to make you afraid of your concentrator and turning up the oxygen to exercise.  Your concentrator does not produce 100% oxygen and this oxygen is diluted by the air that is being breathed in with the oxygen produced by the concentrator.  Let me also point out that these experiments were produced with oxygen under pressure.

Tell your doctor if you are turning up your oxygen to exercise.  If he says that you should not then you need to ask him why.  If he says that it will suppress your desire to breathe then you need to find another doctor.  If he says no because you are a carbon dioxide retainer then you should not increase your oxygen to exercise.