Indirect monitoring of oxygen level by sensors that detect light wave absorption is performed by which device?

• A. Capnography
• B. Electromyography
• C. Pulse oximetry
• D. Thermal sensor

Answer: (C)

The key idea is an indirect, noninvasive method that uses light absorption to estimate how much oxygen the blood is carrying. A pulse oximeter shines light through a small sensor placed on a fingertip, toe, or earlobe. It uses two wavelengths of light that are absorbed differently by oxygenated versus deoxygenated hemoglobin. By comparing how much light is absorbed at each wavelength during the pulsing arterial blood, the device computes the ratio that correlates with oxygen saturation (SpO2). This gives a quick, continuous estimate without drawing blood, making it ideal for monitoring oxygen status at the bedside.

This approach is distinct from other devices listed. Capnography measures carbon dioxide levels and respiratory status, not oxygen saturation. Electromyography assesses electrical activity of muscles. Thermal sensors track temperature changes. So the only device that uses light absorption to monitor oxygen indirectly is pulse oximetry.