Final answer:
The oxygen extracted from inhaled air is influenced by the alveolar Po₂ within the lungs, which is lower than the oxygen concentration in the atmospheric air due to mixing with residual air. The respiratory quotient helps calculate this value, which is critical for determining how much oxygen binds to hemoglobin and is used by the body.
Step-by-step explanation:
The percentage of oxygen extracted from the inhaled air is an important concept in biology, particularly in the understanding of respiratory physiology. The extraction of oxygen occurs in the alveolar spaces within the lungs, where the partial pressure of oxygen in the alveoli, or alveolar Po₂, plays a critical role. The air we breathe contains approximately 21% oxygen, but not all of this oxygen is transferred to the blood. When air enters the lungs, it mixes with residual air in the alveoli, leading to a lower concentration of oxygen than in the atmosphere. The partial pressure of oxygen or Po₂ in inspired air is 150 mm Hg, but after mixing with residual air, the alveolar Po₂ is lower.
The respiratory quotient (RQ) is used to calculate alveolar Po₂, taking into account the partial pressure of carbon dioxide (Pco₂) in the alveoli. With an RQ of 0.8 and a Pco₂ of 40 mm Hg in the alveoli, the alveolar Po₂ can be calculated. This alveolar Po₂ is what determines how much oxygen binds to hemoglobin in the blood and is transported to the body's tissues. The oximeter is a device used to measure the percent saturation of oxygen in the blood, normally ranging from 95-100 percent. When the Po₂ in the blood reaches a partial pressure of around 60 mmHg, the oxygen saturation curve begins to level off as most of the hemoglobin becomes saturated with oxygen.