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The best known explanation of the oxygen effect is the oxygen fixation hypothesis developed by Alexander in 1962, [9] which posited that radiation-induced non-restorable or "fixed" nuclear DNA lesions are lethal to cells in the presence of diatomic oxygen. [10] [11] Recent hypotheses include one based on oxygen-enhanced damage from first ...
For F I O 2 values equal to or greater than 0.5, the alveolar–arterial gradient value should be used in the APACHE II score calculation. Otherwise, the PaO 2 will suffice. [4] The ratio between partial pressure of oxygen in arterial blood and F I O 2 is used as an indicator of hypoxemia per the American-European Consensus Conference on lung ...
The typical partial pressure reference values are oxygen Pa O 2 more than 80 mmHg (11 kPa) and carbon dioxide Pa CO 2 less than 45 mmHg (6.0 kPa). [1] Cause.
Hyperbaric medicine is the medical use of oxygen at a higher pressure level than our atmosphere. [16] Hyperbaric medicine is also known as hyperbaric oxygen therapy. The air we normally breathe is composed of 21 percent oxygen. Hyperbaric treatments utilise 100 percent oxygenated air to treat many conditions. [17]
The oxygen enhancement ratio (OER) or oxygen enhancement effect in radiobiology refers to the enhancement of therapeutic or detrimental effect of ionizing radiation due to the presence of oxygen. This so-called oxygen effect [1] is most notable when cells are exposed to an ionizing radiation dose. The OER is traditionally defined as the ratio ...
When breathing surpasses normal ventilation rate, one has reached ventilatory threshold. For most people this threshold lies at exercise intensities between 50% and 75% of VO 2 max. A major factor affecting one's ventilatory threshold is their maximal ventilation (amount of air entering and exiting lungs).
Hypoventilation exists when the ratio of carbon dioxide production to alveolar ventilation increases above normal values – greater than 45mmHg. If pH is also less than 7.35 this is respiratory acidosis. Hyperventilation exists when the same ratio decreases – less than 35mmHg. If the pH is also greater than 7.45 this is respiratory alkalosis ...
Normal arterial blood oxygen saturation levels in humans are 96–100 percent. [1] If the level is below 90 percent, it is considered low and called hypoxemia. [2] Arterial blood oxygen levels below 80 percent may compromise organ function, such as the brain and heart, and should be promptly addressed. Continued low oxygen levels may lead to ...