Pulse Oximeter: SAQ Solutions

Below are the solutions to the Pulse Oximeter Self-Assessment Questions:

1. 95-100% SpO2.
   As mentioned in the video, normal resting oxygen saturation levels are expected to be above 95%.
2. Each digit is illuminated by a maximum seven segments based on voltage.
   These displays are fairly common throughout many LED numerical applications. These displays have the faint “8” showing in the background made by each LED segment of the display when not illuminated.
3. Oxy-hemoglobin absorbs more IR light, while deoxy-hemoglobin absorbs more red light.
   These differences in absorption is the reason absorbance can be used to quantify SpO2 levels! The differences in these values is compared in the ratio (red light)/(IR light) and compared to a calibration curve for oxygen saturation.
4. Changes in light absorbance, requires photodetector/photodiode and Red and IR LED lights. 
   Like blood oxygenation, pulsatile flow can also affect light absorbance in both the red light and IR light regions. Therefore, periodic changes in these absorbances can be used to find heart rate when plotted against time.
5. False; neonatal measurements require the pulse oximeter be placed at the hands/feet due to their small size. 
   The pulse oximeter’s LEDs must be able to traverse the patient’s blood supply properly to get a accurate absorbance and therefore oxygen saturation reading. Therefore, the body part that it accesses must be big enough to fit snugly on the patient.