What is the Required Inspired Oxygen Consumption during Anesthesia?
Oxygen moves down a partial pressure gradient from inspired gas, through alveolar gas, arterial blood, systemic capillaries and cells, to reach its lowest level within the mitochondria where it is consumed (Figure 1). The steps by which the Po2 decreases from inspired gas to the mitochondria are known as the oxygen cascade and are of great practical importance. Any one step in the cascade may be increased under pathological circumstances and this may result in hypoxia. Within limits, the effect of certain increased steps in the cascade can be offset by raising the concentration of oxygen in the inspired gas. However, the quantitative relationships are totally different depending on which step in the cascade is abnormal.
KeywordsBarometric Pressure Alveolar Ventilation Inspire Oxygen Concentration Venous Admixture Pathological Circumstance
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