The gold standard for oxygenation measurement is the measurement of arterial partial pressure of oxygen, which is represented as PaO2. This measurement reflects the amount of oxygen dissolved in the plasma and provides an accurate assessment of the oxygenation status of the blood.
While SpO2, which indicates peripheral capillary oxygen saturation measured by pulse oximetry, is widely used in clinical settings due to its non-invasive nature, it can be affected by various factors such as inadequate perfusion, skin pigmentation, and the presence of carbon monoxide. Therefore, while SpO2 is essential for quick assessments and continuous monitoring of oxygen saturation, it does not provide the precise measurement that PaO2 does, which is typically evaluated through arterial blood gas (ABG) analysis.
In contrast, ETCO2 (end-tidal carbon dioxide) measures the concentration of carbon dioxide in exhaled air and provides information about ventilation rather than oxygenation. FiO2 (fraction of inspired oxygen) indicates the percentage of oxygen in the air we breathe but does not measure how well oxygen is being delivered to or utilized by the tissues.
Thus, the measurement of PaO2 is critical for assessing the effectiveness of oxygen therapy and is considered the definitive standard for determining oxygenation in