My Co-worker Gets Dizzy And Lightheaded When Moving. He Has

My co-worker gets dizzy and lightheaded when moving. He has been smoking for about 6 years. We applied 15L of 02 via NRB mask. We've taken base line vitals 3 separate times and they show regular. We also gave him water, laid him down and elevated his feet. Now he is sitting with his head down on the table and states the dizziness has improved a little. Is there anything else we can do for him? Thank you.