Looks like a pneumothorax but it aint. During/immediately after being turned in bed, ICU patients often drop their sats, and may have decr air entry on the new dependent side. This is probably due to lung secretions moving to the new dependent side.
Often just need suctioning and an increased FIO2 for a few minutes till they sort themselves out.
Occasionally need increased PEEP or hand-bagging to reinflate them.
Sometimes need a bronchoscopy to suck the snot out of the bronchi. These ones will have a lobe or lung whited out on CXR. d/w boss.
Pneumothoraces do happen but are rare (usually post trauma).
If in doubt get do bedside ultrasound for pneumothorax and urgent CXR.
Unlikely to need “stat” needle decompression in ICU - but tension pneumothoraces do happen. If you get the above picture + falling BP treat as tesnion penumothorax