We all know that oxygen is an indispensable gas for human survival, and without oxygen, life will pass in seconds. But what I never expected was that the oxygen content was too high and even damaged the human body! What the hell is going on? It all starts with the discovery of oxygen...
The bumpy experience of oxygen being found
Human research on oxygen can be traced back to ancient times. Early chemists thought that when an object burned, it was as if something had escaped. For a long time, it was thought that this thing was sulfur, and the Prussian king's physician Starr called it "burning hormone", which means the element of fire.
The "combustible theory" was proposed to be the biggest obstacle in the oxygen discovery process. The erroneous but extremely popular "theory of burning hormones" has undergone a relatively long historical process, almost throughout the eighteenth century. It was not until the emergence of the "oxidation theory" that it replaced this stereotypical statement and became the first scientific chemical theory in the history of modern chemistry.
In 1774, when the British chemist Presty lit up the oxide mercury, he obtained a new gas that could both fuel combustion and support human breathing, which he called "de-flammable air". Considering that candles burn faster in an oxygen environment, it is proposed that breathing such a gas may accelerate aging due to the rapid consumption of living substances, or that this gas is toxic (also quite forward-looking!). ）。
Priestley
Later, the French chemist Lavoisier repeated Prestri's experiment and also came to the conclusion that combustion was partially combined with the purer part of the air, overturning the "combustible theory". It was officially named (Oxygene) "oxygen" in 1777, meaning the element of acid. Since then, oxygen has taken on its own name.
Lavoisier and his lab
In 1887, the famous French gas physiologist Paul Bert described the toxicity of oxygen in detail in his famous monograph "Barometric Pressure Physiology". He found that oxygen was toxic to insects, molluscs, earthworms, fungi, sprouted seeds, birds, and a variety of other animals. This intoxication is characterized by rapid neurologic abnormalities (convulsions) and is therefore called acute oxygenosis (central nervous system oxygenosis, also known as the Bert effect). This is the first time that oxygen has been systematically demonstrated to be toxic.
Paul Bert(1833.10.17-1886.11.11)
In 1897, pathologist James Lorrain Smith discovered that even breathing at high concentrations of oxygen at atmospheric pressure can cause lung damage similar to bronchopneumonia, which is also known as chronic oxygen poisoning (Lorrain Smith effect) because of the relatively long time this damage occurs. His son, Little Halane, once tried to breathe oxygen under high pressure and had a major seizure, personally venturing out to try hyperbaric oxygen toxicity (a cruel man!). ）。 It was also the first documentation of acute oxygen poisoning in humans.
John Burdon Sanderson Haldane FRS(1892-1964)
At first scientists discovered that oxygen was toxic, seemingly targeting only brain and lung tissue, but as in-depth research gradually discovered that the toxicity of oxygen was widespread, and it was toxic to almost all tissues and organs.
Is oxygen really "poisonous"?
At present, the mechanism of oxygen poisoning mainly includes the following hypotheses: oxygen free radical theory, enzyme inhibition theory, amino acid transmitter imbalance theory, neuro-humor theory, etc.
It has been found that hyperbaric oxygen can directly stimulate vascular smooth muscle, causing vasoconstriction, increasing capillary permeability and tissue edema; in addition, hyperbaric oxygen inhibits the activity of various enzymes in the body, especially enzymes containing thiol groups. Enzyme activity in the body during a variety of metabolic pathways, including the citric acid cycle, is inhibited. Inhibition of the tricarboxylic acid cycle makes glucose aerobic metabolism disorder cause metabolically active tissues and organs such as heart, liver, kidney and other energy supply disorders, impaired function; hyperbaric oxygen can also inhibit the activity of polytransmitter metabolic enzymes; the study also found that long-term hyperbaric oxygen environment can cause peptide disorders in pulmonary nerves - endocrine cells.
Since 1964, when Gerrschman and Gilbert proposed the understanding that oxygen poisoning is caused by the excessive production of oxygen radicals, it is now widely believed that the root cause of oxygen poisoning is the damage caused by excessive production of oxygen radicals under hyperbaric oxygen conditions and beyond the body's defense capabilities.
We all know that oxygen is a series of tissue metabolism in the human body, maintaining the normal function of multiple organs and other necessary substances, the average person often breathes oxygen by breathing outside air.
But in fact, oxygen itself is not toxic, only inhalation of pure oxygen and hyperoxia, that is, oxygen partial pressure is too high, may lead to the increase in the difference between the oxygen partial pressure between the blood and tissue cells before, causing oxygen to accelerate the diffusion, exceeding the body's ability to clear, and then causing oxygen poisoning, damaging the cells and tissues in the body. Oxygen poisoning is mainly divided into three types: pulmonary oxygen poisoning, cerebral oxygen poisoning, and ocular oxygen poisoning.
1. Pulmonary oxygen poisoning: nasopharyngeal pain, retrosternal pain, cough, dyspnea and other manifestations may occur, and the lung capacity will decrease and the partial pressure of arterial blood oxygen will also decrease;
2. Cerebral oxygen poisoning: mainly manifested as visual and hearing impairment, nausea, convulsions, syncope, etc., and can appear comatose in severe cases, and even endanger life;
3. Ophthalmic oxygen poisoning: there are often manifestations such as vision loss and visual field reduction, which will induce eye diseases such as myopia, cataracts, acute fundus ischemia, and even induce retinal detachment, resulting in blindness.
Oxygen poisoning is mainly more common in people who inhale pure oxygen for a long time and at high flow. It is generally seen in patients with a disease who need oxygen, but may also be required for activities such as diving.
What should I do if I am poisoned by oxygen?
When such a situation occurs, oxygen inhalation should be controlled in time and emergency treatment should be carried out. If possible, seek medical attention in time, stop oxygen inhalation under the guidance of a doctor, or adjust oxygen to an appropriate oxygen concentration.
Currently, routine hyperbaric oxygen regimens use intermittent oxygen use. A widely used scheme is to inhale pure oxygen for 20 minutes followed by compressed air for 5 minutes.
In terms of drug therapy, antioxidants and free radical scavengers can play a role in reducing oxidative stress damage, in addition, NO inhibitors, drugs that regulate amino acid metabolism in the brain can also significantly combat oxygen convulsions.
Unexpectedly, I didn't expect that oxygen originally had such a bumpy experience. However, oxygen poisoning is really not to be underestimated
Reference: Science Network Sun Xuejun. Discovery of oxygen toxicity
Sheng Genyu. Chemists who independently discovered oxygen——Priestley and Scheler[J]. Teaching Chemistry, 2011, 000(002):59-62.
CHEN Wei. Evaluation of Lavoisier and oxygen invention rights[J]. China Science and Technology Wealth, 2009, 000(016):94.
Wu Guiying, Liao Zhongli, Li Ning. Research progress on the occurrence of oxygen poisoning and its prevention and control[J]. Chongqing Medical Journal, 2009, 38(8):3.