I have mild ILD with Lupus and RA. I was diagnosed at National Jewish Hospital (NJH) in Denver, an excellent resource. Mayo Clinic is also an excellent resource for this. The response here from Sue is excellent. The tests for still needing oxygen is pulse oximetry (finger sensor), 6 minute walk test ( tests oxygen saturation levels during exercise) and I would recommend getting tested for sleep apnea ( causes low oxygen levels associated with breathing cessation during sleep). Sleep apnea is common in RA and can aggravate ILD and cause many other problems. It is treatable, usually with CPAP, and requires a sleep study for diagnosis or a nighttime pulse oximetry test (easy screening test for sleep apnea.)I hope this helps you and your wife.