Appendix to ``Deligne's integrality theorem in unequal characteristic   and rational points over finite fields'' by H\'el\`ene Esnault
  One extends P. Deligne's notion of integrality over a finite field for a $\ell$-adic sheaf on a scheme of finite type over a local field with finite residue field. One shows that this integrality notion is preserved by $Rf_!$, as it is over a finite field after P. Deligne. 
Pierre Deligne and H\'el\`ene Esnault