Fetus scalp electrode instrument

Claim 1

A fetus scalp electrode instrument comprising: a flexible outer tube of sufficient length to reach a fetus scalp from outside the mother's body through her passages and having a first end serving as the insertion end thereof and a second end serving as the control end thereof; a flexible electrode drive tube telescoping within said outer tube, longer than said outer tube and having a first end serving as the insertion end thereof and a second end serving as the control end thereof, said second end of said electrode drive tube protruding from said second end of said outer tube; a collar on said second end of said drive tube for facilitating manipulation of said electrode drive tube within said outer tube; an electrode-carrier plug adjacent to said first end of said electrode drive tube and normally located within said outer tube and having a rear face facing the interior of the length of said drive tube and a front face facing in the opposite direction; a grasping electrode having a root portion embedded in said electrode-carrier plug, said grasping electrode being made of spring metal wire, protruding from said front face of said plug and having opposed arms diverging, from said root portion embedded in said plug, to a maximum width which, when said electrode is not constrained by said outer tube, substantially exceeds the outer diameter of said outer tube, said opposed arms being crossed on the side of their place of maximum divergence away from said plug and being hooked over beyond the crossing so that the ends of the arms are in a pincer configuration which is closed, when said electrode is unconstrained, to a degree necessary for grasping a bit of scalp and which is open when the opposed arms are constrained at their said places of maximum divergence by being confined in said outer tube; a reference electrode at least partly embedded in said plug, for increasing the stray field of the pair of electrodes constituted by said grasping and reference electrodes, and a pair of electrode leads running through said drive tube, each having one end respectively connected to each of said electrodes and having their other ends brought out of said drive tube as well as out of said outer tube, whereby the instrument may be inserted to approach closely the scalp of a fetus with the grasping electrode open at or near the end of the outer tube and the outer tube may then be retracted while keeping the electrode drive tube stationary or slightly advancing until the grasping electrode, which was previously confined in open position by the outer tube, is advanced relative to the outer tube to a point at which it is no longer confined and closes to grasp a portion of fetus scalp.