I have never tried the “vacuum pump”. It seems like something I wouldn’t like — but according to the medical literature, they are quite effective.
Here is an article which suggests that they work the same way as Viagra does – via the nitric oxide system. Worth a try?
Here’s the article: LINK HERE.
Or, to see the article, put this in your browser: http://www.ncbi.nlm.nih.gov/pubmed/20457493