If my blood oxygen level falls to 88 while sleeping, do I need oxygen at night?

Home oxygen. The following CMS guidelines would help: https://www.cms.gov/Outreach-and-Education/Medicare-Learning-Network-MLN/MLNProducts/Downloads/Home-Oxygen-Therapy-Text-Only.pdf
One of the criteria is oxygen saturation less than 88% while at rest.
Hope that helps.
.