An implantable catheter defining a plurality of fluid exits responsive to a first range of pressure on a fluid agent for delivering substantially the same flow rate of the agent through each of the exits into spaced infusion sites and responsive to a second range of pressure less than a threshold ...http://www.google.com.au/patents/US5752930?utm_source=gb-gplus-sharePatent US5752930 - Implantable techniques for infusing equal volumes of agents to spaced sites 
