There could be many reasons behind the drop in oxygen saturation levels in the blood. The medical professionals will need to diagnose the root cause of such a decline and start suitable treatment. Usually, oxygen is given to the patient via a face mask to regularise the level of oxygen saturation levels. If the drop in oxygen saturation level is significant, the patient may be put on artificial respiration using a ventilator. You should never ignore the declining oxygen levels and consult your doctor immediately.