http://lungdiseases.about.com/b/2005/06/14/viagra-helps-children-suffering-from-pulmonary-hypertension.htm
I fond this and I hope it helps i just typed in Viagra and children. I would have copied the article but it was a few pages long.
good luck
michelle
I am sorry I can't answer that question, but my friends mother was told to use it also for this reason. after laughing at the doctor and realized he wasn't kidding, she said she would take it and it has helped her out.
good luck and I hope you can find answers. I will try to google too
michelle