it can be normal or it can be severe or bad. A lot of time some atelectasis is normal if you've been in bed all day and not getting around. That's why you need the pt to take a deep breath a couple times before you do the pulse ox. If they've been in bed all day, have them take a couple of breaths to clear out atelectasis. Atelectasis has nothing to do smoking. It's usually due to pt staying in bed all day.