O2 stats, abnormal or dangerously abnormal?

Normally doctors would want your O2 stats above 92. So 88 is pretty low. It would be normal for a 75 year old man with COPD. But considering what you've been threw it may take you awhile to get back to normal. It all depends on what your stats have been since you've been back at home. If they have been higher than 88 I would definately be concerns. But if 88 has been about the average since returning home I wouldn't worry if I were you.