Anyone got tips for helping a dog with severe bronchitis?

Our german shephard is in real bad shape, apparently he has an extreme case of bronchitis. We've got him on antibiotics and a kind of mucinex-type-thing to get the nasty stuff out of his body, but I'm wondering if anyone has any other tips for stuff we can do with him since he seems like he's really struggling, and the vet was very concerned. He's become pretty lethargic in the last week or so and we're trying not to push him since apparently excitement is not a good idea right now.

I'm feeding him high-quality canned food to keep him eating and give him strength, and we've also been kinda steaming him in the bathroom with a hot shower running for a little bit once a day, which seems to help a lot with getting the goop out of him.