Detecting devices for detecting the proximity of metallic objects relative to a selected position are well known and various devices have been heretofore suggested and/or utilized. Examples of such devices can be found in U.S. Pat. Nos. 3,350,660, 3,744,044, 3,889,249, 3,935,542, 4,004,234 and 4,502,042.
Implantable injection cites for receipt or withdrawal of fluids within the human body through a needle are also known and such devices have heretofore been suggested and/or utilized for allowing body cavity access over relatively long terms without unduly limiting the activities and/or movement of a patient (see, for example, U.S. Pat. Nos. 4,160,454 and 4,543,088).
Various sensing devices have also been heretofore suggested and/or utilized in association with stabbing or puncturing medical devices for sensing various parameters of patient penetration by an implement, for example depth of penetration and completion of cavity wall puncture. Examples of such devices are shown in U.S. Pat. Nos. 4,299,230 and 4,535,773.
While such devices now known have been found to be acceptable for some uses, such devices have not been heretofore suggested and/or have not been found to be fully suitable for assuring placement of, and maintenance of, a medical instrument at a desired location to dependably enable a fluid to be inserted into or withdrawn from a predetermined location, and improvements in such devices are deemed to be still useful and/or needed for such application.