Arterial Oxygen Saturation

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It is known that as altitude increases, atmospheric pressure decreases, as does the partial pressure of oxygen (Hall Table 44-1). That same table demonstrates that the partial pressures of both oxygen and carbon dioxide in the alveoli decrease as well. However, the alveolar water vapor pressure remains unchanged—constant at 47mmHg no matter the altitude (Hall 561). The most deleterious result of these factors is that less oxygen is being delivered to the tissues. Fortunately for me, Guyton and Hall says that altitude has a relatively insignificant effect on arterial oxygen saturation at 9,000ft (Hall Figure 44-1). It is not until 10,000ft that arterial oxygen saturation begins to steeply decline. The physical affects of acute hypoxia according to Hall are “drowsiness, lassitude, mental and muscle fatigue, sometimes headache, occasionally nausea, and sometimes euphoria. These effects progress to a stage of twitchings or seizures above 18,000 feet and end,…show more content…
According to an article in Oxford Journals, one of the first steps in acclimitization is polycythemia. This increase in red blood cells can be seen within the first two days of ascension. However, the author is quick to point out that it is nonetheless a slow process and therefore not nearly as vital to acclimitization as the other factors that come into play, the most crucial of which is the increase pulmonary ventilation (West). Low oxygen is immediately sensed by chemoreceptors in the carotid and aortic bodies, which then send signals to the respiratory centers of the brain, resulting in an increase in respiration. In a matter of only days, acclimitization increases our: “pulmonary ventilation, concentration of red blood cells, lung diffusing capacity, vascularity of tissues, and ability of cells to use oxygen” (Hall
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