Do I need to put blood in a vacuum sealed bag to cook it sous vide in this type of appliance?
Looking at the photos in the webshop it's pretty clear to me that you're still supposed to bag whatever food goes in it. It will make clean up of the machine easier and you don't want blood residues on it for your next batch of food. 

Perhaps you don't need to vacuum seal it, just squeeze out as much air as possible with the vacuum displacement method and trap the edge of the bag between the pot and the lid.