Philips M3500B manual Understanding Pulse Oximetry, Pulse Oximetry Sensor

Understanding Pulse Oximetry

Understanding Pulse Oximetry

A pulse oximetry sensor sends light through patient tissue to a receiver on the other side of the sensor. As Figure 5-1 shows, light emitting diodes transmit red and infrared light through peripheral areas of the body, such as a finger.

Figure 5-1 Pulse Oximetry Sensor

LED

Photodetector

A photodetector positioned opposite the light emitting diodes compares light absorption before and after pulsation. The amount of light getting through reflects the blood flow in the arterioles. This measurement of light absorption during pulsation is translated into an oxygen saturation percentage and an SpO2 value is displayed.

For accurate SpO2 measurements, the following conditions must apply:

The patient must have perfusion in that extremity.

The light emitter and the photodetector must be directly opposite each other.

All of the light from the emitter must pass through the patient’s tissue.

￿The sensor site should be free of vibration and excessive motion. Power cables should be kept away from the sensor cable and connec- tor.

5-2 Monitoring SpO2