I was going through some papers and ran across this that I thought others might have an interest in; I found it a few months ago and it helped me better understand some of the 'down side' to oxygen therapy:
livestrong.com/article/2342...
"...When it comes to oxygen therapy, there can be too much of a good thing. Prolonged administration of highly concentrated oxygen can potentially damage the lung lining tissues and air sacs, a condition known as pulmonary oxygen toxicity. The risk for this side effect of oxygen therapy comes into play primarily when patients on home treatment increase the oxygen flow rate to a level higher than prescribed.
The risk of pulmonary oxygen toxicity proves highest when inhaling pure oxygen for several hours to days. Coughing is typically the first symptom of pulmonary oxygen toxicity. Irritation of the large airways caused by the highly concentrated oxygen provokes this symptom. With continued exposure, damage to the lung tissues may cause fluid leakage into the air sacs, accompanied by increasingly severe shortness of breath..."
Hope this helps...
Duncan