{"id":987474979,"date":"2024-09-12T13:45:46","date_gmt":"2024-09-12T13:45:46","guid":{"rendered":"https:\/\/courses.asiascubainstructors.com\/lessons\/physics4-partial-pressure-copy-copy\/"},"modified":"2024-09-13T14:38:37","modified_gmt":"2024-09-13T14:38:37","slug":"physics-2-responses-to-diving","status":"publish","type":"lessons","link":"https:\/\/courses.asiascubainstructors.com\/de\/lessons\/physics-2-responses-to-diving\/","title":{"rendered":"Restricted content"},"content":{"rendered":"

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Physiology<\/h1>\n

 <\/p>\n

2. Responses to diving<\/h2>\n

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Nitrogen (gas) Narcosis:<\/h3>\n

Breathing too much nitrogen can cause a narcotic effect (nitrogen narcosis<\/strong><\/em>).\u00a0 Narcosis can occur when diving to 30m or deeper, it varies from one diver to the next and is not predictable. Symptoms can include euphoria (feeling happy), anxiousness (fear), panic, dizziness, tunnel vision.
Symptoms which are not directly hazardous \u2013 but impaired judgment and loss of co-ordination can lead to a hazardous situation. Ascending a few meters usually reduces the narcosis. Diving with enriched air – Nitrox, does not reduce the risk of nitrogen narcosis because oxygen can also have a narcotic effect.<\/p>\n

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Oxygen Toxicity<\/h3>\n

Central nervous system (CNS) toxicity<\/em><\/strong> \u2013 is caused by breathing too much oxygen. Recreational divers risk CNS toxicity when breathing oxygen at partial pressures greater than 1.4 bar.
The most serious symptom is a convulsion which can cause the diver to lose his mouthpiece and drown. Other signs and symptoms include: visual disturbances, ear ringing, nausea, twitching, irritability and dizziness (VENTID). However, convulsions typically occur\u00a0without warning.<\/p>\n

Pulmonary toxicity<\/em> <\/strong>\u2013 caused by exposing the lungs to high partial pressures of oxygen over a longer period.
Signs and symptoms include burning in the chest and an irritated cough. It\u00a0is unlikely in recreational diving.<\/p>\n

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Decompression Sickness<\/h3>\n

Gases dissolve into liquids when the pressure on the liquid is increased.
The human body is primarily water. When a diver breathes gas under pressure, gases dissolve into the body tissues.
Oxygen used by the body, but nitrogen (and any other inert gas) is not.
When the nitrogen pressure in the lungs is greater than in blood, nitrogen (in the alveoli) dissolves into blood and then into the tissues.
The amount of nitrogen that the body absorbs depends on the depth and the length of the dive. It also depends on the breathing gas. (Enriched air has less nitrogen).<\/p>\n

Wenn the diver ascends to the surface, nitrogen pressure in tissues becomes higher than the surrounding pressure.
The nitrogen pressure in the blood exceeds pressure in lungs and nitrogen dissolves from blood into the alveoli in the lungs and is exhaled.
If the difference is within limits, nitrogen dissolves harmlessly into blood and then slowly out through exhalations
If body has absorbed too much nitrogen, the body can not eliminate (breath out) as fast as it comes out of solution and bubbles form in the blood and tissues.
nitrogen bubbles can block the oxygen delivery to the body tissues. This is known as decompression sickness<\/strong><\/em>.<\/p>\n

It is very common for divers to have microscopically small nitrogen bubbles in their body, after a dive. These harmless bubbles are known as silent bubbles<\/strong><\/em>. After time, and again, if too much nitrogen has been absorbed during the dive, these silent bubbles can accumalate to form larger bubbles.<\/p>\n

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DCS signs and symptoms<\/h3>\n

DCS signs and sympoms tend to be delayed. In about half the cases, it appears within an hour but it can take up to 36 hours for signs and symptoms to occur. It often worsens during the first few hours.<\/p>\n

There are two types of DCS, depending on the signs and symptoms and severity.<\/p>\n

Type I DCS<\/strong><\/em>\u2013 (pain-only DCS) is not immediately life-threatening or likely to cause long-term disability. This results in a skin rash, often in parts of the body that have a lot of fat tissue.<\/p>\n

Type II DCS<\/strong><\/em> affects the nervous system and may be immediately life-threatening.
Signs and symptoms include tingling, numbness, paralysis, stroke-like symptoms, unconsciousness and cardiac or respiratory arrest. When bubbles travel to the brain, signs and symptoms can include blurred vision, confusion, headache, unconsciousness and death.<\/p>\n

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Predisposing factors<\/h3>\n

Because everyone has a different physiology, the predisposition to DCS varies from person to person. Factors that may predispose a diver to DCS:<\/p>\n

Fat tissue<\/strong> \u2013Nitrogen is more soluble in fat.
Age<\/strong> \u2013Circulatory systems become less efficient; increased percentage of fat and reduced fitness level could decrease nitrogen elimination.
Dehydration<\/strong> \u2013Reduced quantity of blood in circulation slows nitrogen elimination.
Injuries or illness<\/strong> \u2013Injuries or illness can affect the efficiency of the circulatory system.
Alcohol<\/strong> \u2013Drinking alcohol before or after diving accelerates circulation, dilates capillaries and promotes dehydration.
Cold water<\/strong> \u2013A diver starts a dive warm with normal circulation, but cools and circulation to the extremities is reduced, slowing nitrogen elimination.
Heavy exercise<\/strong> \u2013 Working hard during a dive accelerates circulation thus more nitrogen than normal dissolves into the body. After or immediately before a dive, heavy exercise accelerates circulation, altering nitrogen elimination and stimulating the production of microbubbles.
Altitude or flying after diving<\/strong> \u2013Dive tables and computers are based on surfacing at sea level \u2013exposure to lower pressure increases tissue pressure gradient and may increase bubble formation.
History of DCS<\/strong> \u2013Studies of divers suggest that someone who has had DCS will be more predisposed to it in the future.<\/p>\n

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| <\/span>
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Background<\/strong><\/span><\/p>\n

Patent Foramen Ovale (PFO)<\/h3>\n

A PFO, commonly known as \u2018hole in the heart\u2019 is an opening in the heart (from the right atrium to the left atrium) that normally grows close after birth. In about 30% of the normal and healthy population, however the PFO does not grow completely closed.<\/p>\n

A PFO increases the risk of decompression illness because bubbles may pass directly from the venous blood (oxygen poor blood, returning to the heart), into the arterial circulation that carries oxygen to the tissues.<\/p>\n

<\/span><\/p>\n

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Treatment for DCS<\/h3>\n

Treat all cases serious. Give the patient oxygen, preferably 100 percent. Keep the patient lying down with the head supported. Provide primary care and arrange transport to the nearest medical facility.<\/p>\n

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Lung over expansion injuries<\/h3>\n

This can happen when a scuba diver holds his breath while ascending to the surface. The reduced pressure causes the lung volume to increase. This can cause a tear in the lungs through which air can escape \u2013 hence, the term \u2018ruptured lung\u2019. Scuba diving with a lung congestion increases the risk of a lung over expansion injury, and so does loss of surfactant (fluid protecting the lung surface) due to smoking.<\/p>\n

There are four types of injury that can occur:<\/p>\n

Air embolism:<\/strong><\/em> This is also called arterial gas embolism (AGE). The alveoli and pulmonary capillaries rupture allowing air to directly enter the bloodstream and flow into the arteries. This is serious and immediately life threatening, because the bubbles flow through the arteries to the brain.<\/p>\n

Pneumothorax:<\/strong><\/em> The air from the rupture goes between the lung and chest wall, causing the lung to collapse. The diver will have chest pain and may cough up blood.<\/p>\n

Mediastinal emphysema:<\/strong><\/em> The air from the rupture accumulates in the centre of the chest over the heart and interferes with circulation; the diver may feel faint and short of breath.<\/p>\n

Subcutaneous emphysema:<\/strong><\/em> The air from the rupture accumulates in the soft tissues under the skin, at the base of the neck. The diver\u2019s voice may change and the skin may crackle to the touch.<\/p>\n

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Decompression illnes<\/h3>\n

Decompression sickness is caused by nitrogen bubbles<\/em> coming out of solution.
A lung overexpansion injury is caused by air bubbles<\/em> entering the body tissues through a ruptured lung.
DCI stands for decompression illness and covers DCS and all lung-overexpansion injuries.<\/p>\n

The signs and symptoms for decompression sickness and lung overexpansion injuries are very similar, however, for a lung overexpansion the signs and symptoms normally occur directly after the dive while for decompression sickness it can take several hours or even days.<\/p>\n

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