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As a person breathes, the body consumes oxygen and produces carbon dioxide. Base metabolism requires about 0.25 L/min of oxygen from a breathing rate of about 6 L/min, and a fit person working hard may ventilate at a rate of 95 L/min but will only metabolise about 4 L/min of oxygen [10] The oxygen metabolised is generally about 4% to 5% of the inspired volume at normal atmospheric pressure, or ...
[3] [4] The inert gas and unused oxygen is kept for reuse, and the rebreather adds gas to replace the oxygen that was consumed, and removes the carbon dioxide. [3] Thus, the gas recirculated in the rebreather remains breathable and supports life and the diver needs only to carry a fraction of the gas that would be needed for an open-circuit system.
Another method of carbon dioxide removal occasionally used in portable rebreathers is to freeze it out, which is possible in a cryogenic rebreather which uses liquid oxygen. The liquid oxygen absorbs heat from the carbon dioxide in a heat exchanger to convert the oxygen to gas, which is sufficient to freeze the carbon dioxide.
Underwater breathing apparatus can be classified as open circuit, semi-closed circuit, (including gas extenders) or closed circuit (including reclaim systems), based on whether any of the exhaled gas is recycled, and as self-contained or remotely supplied (usually surface-supplied, but also possibly from a lock-out submersible or an underwater habitat), depending on where the source of the ...
The concentration of oxygen in water is lower than air and it diffuses more slowly. In a litre of freshwater the oxygen content is 8 cm 3 per litre compared to 210 in the same volume of air. [7] Water is 777 times more dense than air and is 100 times more viscous. [7] Oxygen has a diffusion rate in air 10,000 times greater than in water. [7]
Gills are tissues which consist of threadlike structures called filaments. These filaments have many functions and are involved in ion and water transfer as well as oxygen, carbon dioxide, acid and ammonia exchange. [4] Each filament contains a capillary network that provides a large surface area for the exchange of gases and ions. Fish ...
Climate change is going to wreak havoc on the world’s oceans, according to two new studies, depleting the warming waters of the oxygen that fish and other sea life need to survive.
In fish, gill lamellae are used to increase the surface area in contact with the environment to maximize gas exchange (both to attain oxygen and to expel carbon dioxide) between the water and the blood. [3] In fish gills, there are two types of lamellae, primary and secondary. The primary gill lamellae (also called gill filament) extends from ...