If my husbands oxygen level got down in the 50s after getting a chest tube, can he have some brain damage?

Good question. I am assuming when he had the chest tube put in he was monitored and had some sedation? Sometimes the pulse oximeter readings can be off (movement, poor contact)...Especially when procedures are being done. I would bring your concerns to the treating m.D's, but i suspect that the dip was only transient and did not cause any permanent damage.