How long does it take a baby to recover from RSV?

My baby is a little over two weeks old and has RSV. He has not had a fever, is gaining weight, perfect on every account except for RSV. The thing that is bothering him is he is unable to keep up a good oxygen level. He is on the lowest oxygen level that they have. His lungs are cleared up, he is just congested. When he sleeps, his oxygen level goes down a bit to about 89 percent. Im wondering if when we sleep, if we breathe less. When he was awake earlier, his oxygen level was about 95, and has gone down when he started sleeping. Any advise or tips?