Nebulizer or other treament for extreme cough?

FirstTimePregnancy

My head cold has now moved into my chest and my doctor prescribed an inhaler.  After two days of using the inhaler, it is not working.  One of my friends suggested a nebulizer as a possible treatment but I have never used one of these and am not sure if it would be safe during pregnancy.  Has anyone here used a nebulizer while pregnant or been prescribed something else that helped with a constant cough (from the chest, not due to scratchy throat)?  I'm very sleep deprived and any insight would be greatly appreciated!  Thanks!