Thank you LadyJane.
Today we brought Chibi to the emergency vet. The poor thing only had 92% oxygenation. (They tested him with a pulse oximeter.) They said that they like to see 98-100%. Good thing we didn't wait!
They will give him supplemental oxygen and a bronchodilator and keep him overnight. They will be doing more diagnostics. Probably will take another X-ray and schedule a fluoroscopy.