L ' Apnea can be voluntarily achieved (for example, through the act of "holding the breath").
In normal humans can not store much oxygen in the body. Apnea of \u200b\u200bmore than a minute's duration therefore leads to a severe lack of oxygen in the bloodstream. Permanent brain damage can adverse after about three minutes and death within minutes after it inevitably follows if ventilation is not restored.
A person without training can not sustain voluntary apnea for more than one or two minutes. The reason for this is that the breathing rate and volume of each breath are tightly regulated to maintain constant values \u200b\u200bof tension of carbon dioxide (CO2) and pH of the blood.
In apnea, the CO2 is removed through the lungs and accumulates in the blood. The resulting growth of CO2 tension and the collapse of the pH resulting in stimulation of the respiratory centers of the brain, which can not be overcome voluntarily. However, tolerance to apnea may be exercised.
The ancient technique of immersion in apnea requires you to hold your breath and the best free-divers can indeed hold his breath underwater for more than eight minutes .
Many people have independently discovered that voluntary hyperventilation, performed before beginning voluntary apnea, can hold their breath longer. Some of them incorrectly attribute this effect to an increase of oxygen in the blood, not realizing that it is instead of a decrease in the rate of CO2 in the blood and lungs. The blood that leaves i polmoni è in normalità completamente saturato di ossigeno, quindi
l'iperventilazione non può aumentare la quantità di ossigeno disponibile.
Abbassare la concentrazione di CO2 aumenta invece il tempo che passa prima che i centri respiratori vengano stimolati. Questo errore ha portato alcuni ad usare l'iperventilazione come mezzo per aumentare il tempo di immersione, senza realizzare che c'è il pericolo che il corpo possa esaurire l'ossigeno mentre è sott'acqua, prima di sentire il bisogno di respirare, perdendo quindi improvvisamente conoscenza come risultato. Se una persona perde coscienza sott'acqua, ci sono considerevoli probabilità di morte per annegamento.
In normal humans can not store much oxygen in the body. Apnea of \u200b\u200bmore than a minute's duration therefore leads to a severe lack of oxygen in the bloodstream. Permanent brain damage can adverse after about three minutes and death within minutes after it inevitably follows if ventilation is not restored.
A person without training can not sustain voluntary apnea for more than one or two minutes. The reason for this is that the breathing rate and volume of each breath are tightly regulated to maintain constant values \u200b\u200bof tension of carbon dioxide (CO2) and pH of the blood.
In apnea, the CO2 is removed through the lungs and accumulates in the blood. The resulting growth of CO2 tension and the collapse of the pH resulting in stimulation of the respiratory centers of the brain, which can not be overcome voluntarily. However, tolerance to apnea may be exercised.
The ancient technique of immersion in apnea requires you to hold your breath and the best free-divers can indeed hold his breath underwater for more than eight minutes .
Many people have independently discovered that voluntary hyperventilation, performed before beginning voluntary apnea, can hold their breath longer. Some of them incorrectly attribute this effect to an increase of oxygen in the blood, not realizing that it is instead of a decrease in the rate of CO2 in the blood and lungs. The blood that leaves i polmoni è in normalità completamente saturato di ossigeno, quindi
l'iperventilazione non può aumentare la quantità di ossigeno disponibile.
Abbassare la concentrazione di CO2 aumenta invece il tempo che passa prima che i centri respiratori vengano stimolati. Questo errore ha portato alcuni ad usare l'iperventilazione come mezzo per aumentare il tempo di immersione, senza realizzare che c'è il pericolo che il corpo possa esaurire l'ossigeno mentre è sott'acqua, prima di sentire il bisogno di respirare, perdendo quindi improvvisamente conoscenza come risultato. Se una persona perde coscienza sott'acqua, ci sono considerevoli probabilità di morte per annegamento.
EMBOLISM
The air around us, however, is not only composed of O2 and CO2, but also contains other gases, more or less inert, which dissolve in the blood passively: the main nitrogen. The ability of blood to contain nitrogen varies with the pressure: this means that if the standard atmospheric pressure can dissolve a certain quantity, subjecting the entire body at a higher pressure (scuba diving) the blood is able to accept more; on the other hand, subjecting the body to a lower pressure (high altitude), it accepts less. The problem therefore arises in the face of abrupt changes in pressure drop, ie when rapidly reduces the blood's ability to maintain dissolved nitrogen. Consider the case of a Sub: at a depth of 20 m. His blood is able to contain a quantity of nitrogen was much higher (and as it enters the cylinders there is nitrogen in the blood), where the ascent is too fast your body does not have time to remove the excess nitrogen with breathing and, at the same time, the blood is no longer able to keep it dissolved. The result is that form of nitrogen gas bubbles in the circulation (embolism) that reach the heart and block the function of the pump (death from embolism). In free flight the differences in pressure are much more subtle (to have a problem would require a meteoric rise to around 7000 meters altitude ...) but the issue can become real for those who play both sports (diving, delta): you must wait at least 24 hours between last dive and flying in (high) share .
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