| Patient factors | Device factors | Environmental factors |
|---|---|---|
| Chronic respiratory disease |
Battery level/charge | Extremes of temperature |
| Nail thickness and nail paint or polish | Device condition such as being dusty, dirty, or damaged | Movement or vibration such as transportation |
| Heart rhythm and cardiac output | Size and orientation of light and sensor | Moisture and humidity |
| Skin thickness, perfusion, pigmentation, and temperature |
Device accuracy and calibration (FDA categories):
|
Interference from direct external light sources, including sunlight |
|
FDA indicates US Food and Drug Administration |
||