There are 2 different sized attachments for mouth & nose and only for the nose (not tried).
Our son (otherwise rather fidgety) it enjoys under the mask! He remains 10 minutes sitting quietly, easily distracted and good breathing deeply through the open mouth and nose. It seems to do well to him. Even the "noisy" hum seems rather calm. I personally think it's not annoying. It's more of a "booming" much quieter than the hair dryer. The hose is long enough (chair just behind the door then) you could place the device in a different room.
This small mouthpiece could be smaller for a baby, but it comes anyway to enough if one invests above in the nose (rubber).
For a complete success: mucus running out, coughing could be prevented at the first sign. The only thing that has really helped against the cold (much better than nasal sprays Oderabsaugen and no nagging.) Recommended !!
Tip: to order solution that is not there. Saline we have used has this been going on very young ...