A new disposable electrode model for clinical routine fhr monitoring.

Abstract

A scalp electrode model for transcervical direct FECGand FHR-monitoring has to be judged for two aspects, first for its electric qualities and secondly for its qualities in practical application. Both aspects have been repeatedly discussed [2, 3, 5, 6, 7, 8, 9]. , Using silver-silver chloride coated electrodes [3] signal-to-noise ratio can be raised by minimising electric noise level and high quality FECGand FHR-records can be obtained. Meanwhile it has been stated that high grade steel electrodes which are cheaper to produce than silver-silver chloride electrodes, have a S/N ratio sufficiently high for clinical routine FHR-monitoring [8a], The need to make electrode application procedures easy and safe has lead to quite Solutions depending on the personal experience of the individual designers. Clip model (HON) and its derivative (KLOCK), needle model (SALING), cork-screw model (JUNGE) and its derivative (RUTTGERS), wire hook (CALDEYRO-BARCIA) and its derivative (BAUMGARTEN) all have a common feature: namely, that the different part of the electrode penetrates the skin; there, it is up to a certain depth in a hypodermic position, thus achieving good fixation and good S/N ratio. (The clip model in this respect is a border-line type because penetration of the skin is minimised.) The other, indifferent part of the electrode is usually a coil around the lead wire, thus placing it in the moist environment of the vagina. After the small supply of hand-made cork-screw electrodes had been used up in 1970, it was decided to design a new model, with the same aspects of practical application and clinical routine in mind. In addition it was thought especially important to construct a disposable model, i. e. a model simple in design and cheap to produce. Fig. l shows the new model. The different electrode is a straight steel needle with very small hooks for attachement in the skin. The indifferent electrode is a small steel plate soldered to the reverse side. Different and indifferent electrodes and their wires are wrapped in a small piece of isolating tube, the corpus. The lead wires leave the corpus at right angles, thus minimising the whole length of the non-