Diffusion of oxygen at the tissue level is affected in all the following poisoning except :
Curare is non-depolarizing (competitive) blocker, acts peripherally by causing muscle relaxation (and does not affect O2 diffusion).
Phosgene is an irritant gas causes lower respiratory tract damage.
Carbon monoxide and cyanide are chemical asphyxiants, i.e. prevent O2 from reaching tissue or the tissue from using it.
Carbon monoxide
Curare
Phosgene
Cyanides