Final answer:
The approximate O2 reading context can range from pulse oximetry in medical settings to the calibration of gas mixtures in laboratories. Percent saturation, hypoxemia, and partial pressure are key concepts in determining oxygen levels, whether in human blood or calibration gases.
Step-by-step explanation:
The question posed is related to the determination of oxygen concentration in various contexts. Specifically, it refers to the percent saturation of oxygen as measured by a pulse oximeter, which is a device that applies two wavelengths of light through a thin part of the body to measure the absorption by hemoglobin. Normal readings on a pulse oximeter are between 95-100%, with lower readings indicating hypoxemia. The term hypoxia refers to low oxygen levels without specifying the medium.
When Oxygen levels are measured in blood plasma, following an arterial stick, they are expressed in terms of partial pressure (pO2), generally in millimeters of mercury (mm Hg). In another example, the dissolved oxygen concentration in water is determined using Henry's law, which correlates the solubility of a gas in a liquid with its partial pressure above the liquid.
In a medical context, calibration gases are used for blood gas analyzers, and percentages of CO2, O2, and N2 are calculated to assess the partial pressures of each gas based on the total pressure in a calibration cylinder.