An
oxygen saturation of 65 to 70 is abnormal under any circumstance; awake, asleep, resting or with exercise. The cause could be respiratory, such as obstructive or central sleep apnea, or cardiac, such as cyanotic congenital heart disease. It could also be that your oximeter is giving erroneous results. If these low levels are confirmed or validated, you should begin with a sleep study, in a sleep laboratory.