I Was Injured In Car Accident Dec. 14 And Had

I was injured in car accident Dec. 14 and had ribs 2 and 3 fractured as well as 3 pelvic fractures. While hospitalized my oxygen sat levels were ok during the day, but at night they dropped sometimes below 90%. They did a pulse oximetry test overnight before releasing me and it showed I was below 90% for 331 minutes. I was sent home with oxygen. My doctor ran another overnight test last week and I was below 90% for only 85 minutes. I have never had these problems until this accident. With time, will this correct itself?