Yes as Irene said "glad you posted this question".
I myself also have white, foamy, bubbly with Nebulizing. I have a good amount each time I nebulize and as well during the day. I have to stop every fiftth breath and clear it out into the Solo Cup I keep close by to place it in. I have shown it to at least three pulmonologists and they say they don't know what it is. I think I read, hopefully others may know if this is so, nebulizing brings moisture into the lungs. That doesn't seem right but an infectious disease doctor referred to what I showed him as moisture when I showed him it via the picture I took of the solo cup with the white, foamy, bubbly susbtance in it. I have a hiatal hernia and it is my understanding that we should follow the acid reflux diet etc. with a Hiatal Hernia. I believe it is the silent reflux they speak of. Acid relux can cause a back flow of substances and the constant clearing of the throat. It is so hard to tell what the real source is or if it is multiple problems....including drainage into the throat???? It is also worse after eating. I read on another forum a person speak of the constant 24/7 mucus and they had either acid reflux or the hiatal hernia. I was taken liquid guaifenesin until the other day when I read that it should not be taken with having GERD and probably therefore with a hiatal hernia. I am testing how I do without the guaifenesin along with doing my best efforts with airway clearance. As yet I have only been on the 7% saline solution without any doctor prescribed medications....I feel fine but I am beginning to have soreness at what appears to be the area just above my waist. Probably from trying to release all in my throat and airways and maybe not doing the huff coughing just right? For me I'm not the best at the huff coughing technique as yet. Hope we can keep this question going to see what those of us who have the white , foamy, bubbly and constant need of clearing of the throat have in common as medical problems. My definitive diagnosis is Bronchiectasis, Hiatal Hernia and a supposed small amount of MAI. No antibiotics prescribed as yet.

The white foamy type might be due to something else and not Pseudo but would not hurt to test. I also have the white foamy but along with it plenty of brownish colored plugs. The brownish colored is typical of Pseudo, But the white foamy is not typical. I have read of one other person who mentions it as well. Internet mentions causes to be COPD or Heart or GERD. My pulmo just dismisses it as air getting in during the nebulizing process or some such thing. But I think he is just not sure. The other person who mentioned having this said her Dr was not sure of the cause either. With so much volume you might at least get your heart checked and or gastro Dr.