## 3 Wireless Body Area Network (WBAN)
### Pulse oximeters  
A pulse oximeter is a medical device used to measure the oxygen saturation level (SpO2) in a person's blood. It is a small, portable device that typically clips onto a finger, toe, or earlobe. The pulse oximeter emits two wavelengths of light, typically red and infrared, into the body part to which it is affixed. The device then measures the light absorbed by the blood's oxygen-carrying hemoglobin. Based on this measurement, the oxygen saturation level is calculated and expressed as a percentage. Pulse oximeters are commonly utilized \begin{table}
\begin{tabular}{c c c} \hline \hline
**Feature** & & **Selection Criteria** \\ \hline Accuracy and reliability & \(\bullet\) & The sensor should provide accurate and reliable pulse rate readings, as any inaccuracies can lead to incorrect diagnosis or treatment. \\ \hline Signal quality & \(\bullet\) & The sensor should produce a clear, high-quality signal that medical professionals or automated systems can easily interpret. \\ \hline Comfort and usability & \(\bullet\) & Consider the comfort of the sensor for the patient, as they may need to wear it for an extended period. \\  & \(\bullet\) & Look for sensors that are non-intrusive, lightweight, and easy to use. \\ \hline Sensing technology & \(\bullet\) & Different sensing technologies are available, such as photoplethysmography (PPG), electrocardiography (ECG), or ballistocardiograph (BCG). \\  & \(\bullet\) & Based on the specific needs of the application, suitable technology is chosen. \\ \hline Compatibility & \(\bullet\) & Ensure the sensor is compatible with the intended medical device or system. \\  & \(\bullet\) & This includes interface compatibility, data communication protocols, and power requirements. \\ \hline Environmental considerations & \(\bullet\) & Evaluate the intended use environment, such as temperature, moisture, or electromagnetic interference, to ensure the sensor can withstand and perform well in such conditions. \\ \hline Cost & \(\bullet\) & Consider the cost implications, as medical sensors can vary in price. \\  & \(\bullet\) & Balance the required features and performance with the available budget. \\ \hline Regulatory compliance & \(\bullet\) & Ensure that the selected sensor meets the necessary medical device regulations and certifications, such as FDA approval or CE marking, depending on the use region. \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The main features for selecting a pulse rate sensor. in hospitals and clinics but are also available at home. They are particularly useful for monitoring patients with respiratory or cardiac conditions and determining the general health status of individuals during physical activity or at high altitudes [43]. A blood oximeter can detect asthma, pneumonia, anemia, lung disorders, and other medical conditions. Although a blood oximeter reading of peripheral SpO2 is not always comparable to the preferred arterial SpO2, it is considered safe, convenient, noninvasive, and affordable. The pulse oximetry method is a valuable tool for assessing oxygen saturation in clinical practice [44]. Pulse oximeters work based on the principle of spectrophotometry. They emit two beams of light, typically red and infrared, through the body part where it is attached. Oxygenated hemoglobin (carrying oxygen) absorbs more infrared light, while deoxygenated hemoglobin (without oxygen) absorbs more red light. The pulse oximeter measures how much light the blood absorbs and calculates the oxygen saturation level by comparing the absorbed red and infrared light ratio. This data is then displayed on the device's screen, showing the oxygen saturation percentage (SpO2) and the pulse rate. The output of a pulse oximeter indicates the efficiency with which oxygen is transported to various body regions. Normal oxygen saturation levels range from 95 to 100 percent. Hypoxemia, characterized by insufficient oxygen levels in the blood, may be indicated by values below this range [45]. A common use case of pulse oximeters is their use in airplanes [46].