Neutropenia is a condition characterized by really low blood levels of infection-fighting neutrophils, a specific kind of white blood cell. Mark's white blood cell count has now tanked sufficiently that he is neutropenic. He has been neutropenic before during chemo (several times 2 years ago, and last year) which was a big red flag to put in place barriers to bacteria, like staying away from people, fresh fruits, and raw vegetables, and taking prophylactic drugs to prevent infections. However, this time all those precautions are already in place! This is, as they say, "planned neutropenia", - a reaction to the mega-dose of chemotherapy he got last week.
So basically Mark has major fatigue and nausea, and just has to wait it out. His counts will continue to go down for a few days before the new stem cells "engraft" and start creating new white and red blood cells. This is the part of the process that takes patience and fortitude, - and Mark has plenty of both.
He has also had some visitors today and some walks around the floor (11 laps around the floor equals one mile) and some music and reading. It's a beautiful sunny day to be looking out over the city and Mt. Hood.