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Hyperoxia occurs when tissues and organs are exposed to an excess supply of oxygen (O2) or higher than normal partial pressure of oxygen. In medicine, it refers to excess oxygen in the lungs or other body tissues, which can be caused by breathing air or oxygen at pressures greater than normal atmospheric pressure. This kind of hyperoxia can lead to oxygen toxicity, caused from the harmful effects of breathing molecular oxygen at elevated partial pressures. Hyperoxia differs from hypoxia in that hyperoxia refers to a state in which oxygen supply is too much, whereas hypoxia refers to the state in which oxygen supply is insufficient. Oxygen supplementation is common in the treatment of hypoxemia, an abnormally low level of oxygen in the blood. Hypoxemia can further cause tissue hypoxia as blood is not supplying sufficient oxygen to the rest of the body's tissues and organs, resulting in the need for further supplementation of oxygen. It is estimated that the annual need for supplemental oxygen is around 800,000 individuals with a cost of 1.8 billion dollars. In the environment, it refers to excess oxygen in a body of water or other habitat. ==Signs and symptoms== Associated with hyperoxia is an increased level of reactive oxygen species (ROS), which are chemically reactive molecules containing oxygen. These oxygen containing molecules can cause damage to lipids, proteins, and nucleic acids by reacting to surrounding biological tissues. The human body has naturally occurring antioxidants to combat reactive molecules, but the protective antioxidant defenses can become overrun with reactive oxygen species leading to oxidation of the tissues and organs.〔 The symptoms produced from breathing high concentrations of oxygen for long periods of time have been studied in a variety of animals, such as frogs, turtles, pigeons, mice, rats, guinea pigs, cats, dogs and monkeys. The majority of these studies reported the occurrence of irritation, congestion and edema of the lungs, and even death following prolonged exposures. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「hyperoxia」の詳細全文を読む スポンサード リンク
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