•	To find out if the patient stops breathing at any point during the night and may have sleep apnea.
	Light measurement must be unhindered so nail polish or press on nails may affect the reading.
	Taking a reading in extreme low temperature or when hands are very cold should be avoided as that effects blood circulation.
	Avoid taking readings in extremely bright light as that may render the reading inaccurate.
	If you've recently had interveneous dye injected this may affect results.
	Skin with darker pigmentation my not render accurate readings. The doctor may have to test saturation with a blood draw and compare it to pulse ox readings so establish a new baseline. Try to choose an area where skin is lightest.
Pulse oximetry is a painless and non-invasive method for measuring oxygen saturation in the blood.