Two Types of SpO₂ Sensor Technologies

SpO₂ sensors, also known as pulse oximetry sensors, are widely used in medical devices to measure a patient’s blood oxygen saturation and pulse rate. While there are many variations in design and application, these sensors generally fall into two primary categories: transmissive sensors and reflectance sensors.

1. Transmissive SpO₂ Sensors
Transmissive sensors are the most common type used in hospitals and clinical environments. In this design, the light source (LED) and the photodetector are positioned on opposite sides of the measurement site, typically a finger, toe, or earlobe. Light passes through the tissue, and the detector measures the amount absorbed by oxygenated and deoxygenated hemoglobin. This method provides high accuracy and reliability, making it suitable for critical care monitoring, operating rooms, and intensive care units. Transmissive sensors are available in both reusable and disposable models, offering flexibility for different clinical needs.

2. Reflectance SpO₂ Sensors
Reflectance sensors place the light source and photodetector on the same side of the probe. Instead of light passing through the tissue, it reflects back from the underlying blood vessels and is measured by the detector. This technology is especially useful in cases where traditional sites are not practical, such as on the forehead, wrist, or chest. Reflectance sensors are increasingly integrated into wearable devices and continuous monitoring systems, offering greater versatility and patient comfort.

In summary, transmissive sensors are preferred for clinical precision, while reflectance sensors enable flexibility and wearable applications. Both technologies play a crucial role in supporting modern patient monitoring across diverse healthcare environments.