While it is possible to use Nitrogen in place of carbon dioxide, it is not ideal. Carbon dioxide has a critical point that is just above above room temperature (305K). Nitrogen on the other hand, has a critical point of 126K. An easier replacement for CO2 would be probably be ethane. Ethane, like CO2, becomes supercritical just above room temperature (305K), but unlike CO2 only requires 48 atms (versus 73 atms) of pressure.