Oxygen is a potent drug and has important side effects that are related to the partial pressure of inspired oxygen and duration of exposure. Two types of adverse effects occur, actual toxicity and responses according to normal physiological mechanisms. Absorption atelectasis, acute tracheobronchitis, and acute and chronic parenchymal pulmonary damage are seen with exposure to high partial pressures of oxygen. Possible adverse effects of long-term oxygen therapy in chronic obstructive pulmonary disease include insufficient reversal of hypoxemia, diminished ventilatory drive, parenchymal pulmonary toxicity, and psychological discomfort. The hazards of long-term, low-flow oxygen therapy are far outweighed by its proven benefits. (Pierson DJ. The Toxicity of Low-Flow Oxygen Therapy. Respir Care 1983;28:889-897.
David J Pierson (Fri,) studied this question.