The Doctor of Nursing Practice (DNP) degree is currently being devised. It is not necessarily higher than an Registered Nurse of a holder of a Master of Science in Nursing degree. Though it is billed as a "doctor" degree it not of the PhD level. A DNP is done after obtaining a bachelor's degree. The problem occurs with the fact that since the DNP is a PhD level degree the nurses with DNP degrees will be introducing themselves as doctors. Though in reality they are not exactly medical degree holding doctors of the type that you think of.
A DNP holder will complete 1,000 hours of practical experience after completing a bachelor's. A physican completes far more hours on a usual basis. Furthermore, having a nurse bill herself as a doctor is going to be misleading for the patients, many of whom won't really understand the difference. Overall, I think the DNP degree is a good idea, but they may want to change the name. The DNP is being pushed by Columbia University School of Nursing.