shortness of breath on Folfox and Avastin?

My husband has had 3 treatments - Folfox and Avastin. About a week after the third treatment he began having SOB, but his pulse OX is normal. Has anybody had this side effect? The SOB is really bad even just standing. His Chest x-ray didn't show anything wrong. He was diagnosed with adenoCA rectum May 2011, had radiation Xeloda by mouth - then A&P resection 8/11 with Colostomy. If anyone has had any experience with anything like this surely would appreciate some info.