At lower levels, a mixture of air and oxygen is required to maintain the alveolar pressure. Above this altitude, oxygen needs to be artificially added to the body. The partial pressure of 55 mm Hg is considered the minimum pressure of oxygen required to sustain normal functions. Even at sea level, the alveolar oxygen pressure is only 14% (103 mm Hg).Īs the altitude increases, the partial pressure of oxygen in the alveoli decreases to the point where it cannot cater to bodily functions. This together with the requirement for the pressure difference to be the same between the lungs and the atmosphere, the alveoli cannot take in the entire 21% of the oxygen in the atmosphere. Because this is a continuous process, there is always water vapor and carbon dioxide present in the alveoli. ![]() The body takes in the oxygen, and in return, it passes water vapor and carbon dioxide into the alveoli. This air is then passed into tiny, microscopic structures called alveoli where the gas exchange occurs between the capillaries and the alveoli. ![]() ![]() As oxygen makes 21% of this pressure, the partial pressure of oxygen is 160 mm Hg and that of Nitrogen is 600 mm Hg. The total pressure exerted by these in the atmosphere is 760 mm Hg.
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