Design Input 1
| Requirements | Specifications | Justification |
| 1. Must be able to measure ratio of red light energy to infrared light energy | 1.1. Red light – 660 nm; Infrared light – 940 nm 1.2. Energy detection via photodetector to 95% accuracy | 1.1. Able to distinguish between oxygenated blood (IR-light) and deoxygenated blood (red light) |
Design Input 2
| Requirements | Specifications | Justification |
| 2. Must be able to distinguish between different skin tones | 2.1. Detect the wavelengths of light reflecting from the skin within the range of (red to violet) 2.2. Detect skin tone with RGB scale | 2.1. The RGB of light values reflected from the skin to detect the skin color of the patient so that the appropriate measurement correction can be applied to the patient’s results. |
Design Input 3
| Requirements | Specifications | Justification |
| 3. Must be able to calculate blood oxygen saturation levels while incorporating skin tone | 3.1. Utilize the Beer-Lambert Law to measure within ±3% | 3.1. After measuring energy ratios, blood oxygen saturation is calculated using the Beer-Lambert Law. 3.2. FDA specifies that the ARMS=√(bias2+precision2) and it must not exceed 3%. |
Design Input 4
| Requirements | Specifications | Justification |
| 4. Must alert the user for blood saturation levels | 4.1. The mechanisms must alert the user when the saturation level reaches 95% or below. | 4.1. Low blood oxygen saturation levels indicate respiratory system malfunctioning such as ventilation-perfusion mismatch, reduced diffusion capacity, etc. |
Design Input 5
| Requirements | Specifications | Justification |
| 5. Must have a comfortable fit onto the appropriate body part used for measurement. | 5.1. The fingertip is the best location for oxygen saturation level of above 90%, which is the target level. 5.2. The device must fit finger diameters ranging from 0.390 inches to 0.956 inches. | 5.1. The user should be able to use the device with accuracy and without feeling too much discomfort to enhance the user experience. |
Design Input 6
| Requirements | Specifications | Justification |
| 6. Must have a user-friendly interface | 6.1. Use a minimum of 16 pt font size, adjust based on font style[7] 6.2. Contrast between text and background must be at least 3:1[7] | 6.1. These are the minimum requirements for ADA. i and ii would ensure those with the most need for a user friendly interface have this requirement met. |
Design Input 7
| Requirements | Specifications | Justification |
| 7. Must meet electrical safety standards | 7.1. Devices should follow guidelines specified by IEC 60601-1 | 7.1. Any medical electrical equipment coming into physical contact with the patient to perform its function should not apply any current to the patient or cause the patient any injury or harm. |
Design Input 8
| Requirements | Specifications | Justification |
| 8. Must have a power source | 8.1. Two 1.5 V AAA batteries – disposable[4] 8.2. 5 year battery life 8.3. Pulse oximeter only used about 1 minute at a time | 8.1. Optimal way to power pulse oximeter |