Which statement about oximetry is true?

Which statement about oximetry is true?

• A. It directly measures PaO2
• B. It uses photometrics to determine SaO2
• C. It requires invasive sampling
• D. It cannot monitor oxygen saturation

Answer: (B)

Pulse oximetry estimates how fully the hemoglobin is saturated with oxygen by using light-based photometry at two wavelengths. The device measures how much light is absorbed by oxyhemoglobin and deoxyhemoglobin and converts that into an SaO2 reading. Because it relies on light absorption rather than measuring dissolved oxygen in the blood, it is noninvasive and can continuously monitor oxygen saturation. It does not directly measure PaO2, which would require an arterial blood gas sample, and it is capable of monitoring oxygen saturation rather than being incapable of it.

Pulse oximetry estimates how fully the hemoglobin is saturated with oxygen by using light-based photometry at two wavelengths. The device measures how much light is absorbed by oxyhemoglobin and deoxyhemoglobin and converts that into an SaO2 reading. Because it relies on light absorption rather than measuring dissolved oxygen in the blood, it is noninvasive and can continuously monitor oxygen saturation. It does not directly measure PaO2, which would require an arterial blood gas sample, and it is capable of monitoring oxygen saturation rather than being incapable of it.