Oxygen therapy can often be prescribed for people who have trouble breathing due to lung disease like emphysema. However, it's well known that too much oxygen therapy can worsen lung disease.1
Now, new research this month from Michail Sitkovsky, PhD, a National Institutes of Health (NIH) researcher, and his associates evaluated the underlying causes of so-called oxygen toxicity, and suggested a way to prevent it.2
"This research illustrates, in an animal model, a delicate balance between supplemental oxygen therapy and an innate tissue-preserving process that appears to operate best in low-oxygen conditions," said Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases (NIAID), where the research took place, in a statement.
This study used mice, but Sitkovksy, who is Chief of the Biochemistry and Immunopharmacology Section at the NIAID, believes the findings have implications for people.
Causes of Oxygen Therapy Damage
Oxygen is a necessary element in the body. Our cells get their energy from the interaction between oxygen and food. But lung diseases like emphysema or pulmonary fibrosis reduce lung function to the point that supplemental oxygen is needed.
Supplemental oxygen can save the lives of people with breathing problems. It can potentially improve sleep and mood, increase mental alertness and stamina, and allow the body to carry out its normal functions. But it can harm the lungs if used for long periods, and as such, a prescription is required.3 While the damage associated with oxygen therapy is well-known, the underlying causes haven't been fully explained, Sitkovsky and his team wrote.
Uncovering a Tissue Protecting Molecule
This study is a follow-up to one published three years ago by the same team into the role played by the lung molecule adenosine (ADD-uh-no-zeen) in regulating inflammation.4 Inflammation is initiated by the immune system as a response to infection or injury. But if it goes on for too long, inflamed tissue can become damaged. Thus, there is a mechanism that halts the inflammation after a certain time. In previous work, Sitkovsky and his team found that inflammation leads to reductions in oxygen levels in the inflamed tissues. This, in turn, activates the release of adenosine from surrounding cells. Adenosine enters the cells in the inflamed tissues and halts the inflammation, thus protecting the tissue from excessive damage.
Armed with that knowledge, the investigators theorized that oxygen therapy given to people with lung inflammation might prevent adenosine from being released since oxygen levels fail to drop during the therapy. That was the basis of this study.
Testing A Different Type of O2 Therapy
To answer that question, Sitkovsky and his colleagues induced lung inflammation in three groups of mice. The first group did not receive supplemental oxygen, and while they sustained lung damage, only two of the animals eventually died. A second group of rodents with acute lung inflammation was treated with 100% or 60% oxygen therapy for 2 days. These mice had extensive lung damage and most of them died. Finally, a third group of rodents that had acute lung inflammation were treated with a combination of 100% oxygen therapy and an adenosine-like drug to offset the oxygen-induced damage that was likely to occur. Only two mice in this group died, and lung inflammation did not worsen.
The investigators concluded that highly pure oxygen therapy without the addition of an adenosine treatment worsens pre-existing lung inflammation. "We suggest that these adenosine substitutes be evaluated for their possible usefulness in settings of acute lung inflammation due to infection or other causes, such as asthma or surgical trauma," Sitkovsky stated.
Changes in oxygen therapy protocols to include adenosine substitutes may be valuable to patients, they recommended.
In the meantime, Sitkovsky says he is continuing his research on oxygen therapy.
1. Kazzaz JA, Xu J, Palaia TA, Mantell L, Fein AM, Horowitz S. Cellular oxygen toxicity. Oxidant injury without apoptosis. J Biol Chem 1996 Jun 21;271(25):15182-6.
2. Thiel M, Chouker A, Ohta A et al. Oxygenation inhibits the physiological tissue-protecting mechanism and thereby exacerbates acute inflammatory lung injury. PLoS Biol 2005 May 3;3(6):e174 [Epub ahead of print].
3. American Lung Association. Oxygen Therapy Fact Sheet. Available at: http://www.lungusa.org/site/pp.asp?c=dvLUK9O0E&b=35697. Accessed May 12, 2005.
4. Ohta A, Sitkovsky M. Role of G-protein coupled adenosine receptors in downregulation of inflammation and protection from tissue damage. Nature 2001 Dec 20-27.;414(6866):916-20.
John Martin is a long-time health journalist and an editor for Priority Healthcare. His credits include coverage of health news for the website of Fox Television's The Health Network, and articles for the New York Post and other consumer and trade publications.
