Cable for connecting an electrocardiograph to limb electrodes and chest electrodes

Abstract: The connecting cable uses a multiple-core, multiple-screen strap (1) which is provided at one end with a terminal (6) within which are dischargers (12) for protection against excess voltages and with a connector (13) for removable connection to the electrocardiograph. At two intermediate points, with a suitable distance between them, the strap (1) is provided with clamps (7,8) from which are branched the separate leads (C₁,C₂,C₉,C₁₀;C₃...C₈) for the peripheral and precordial branches. The leads (C₁...C₁₀) are provided at their free ends with plugs (9) for connection to the measuring electrodes, and electrical resistors for protection against excess voltages are preferably housed in the bodies of said plugs (9).

Description: The present invention relates to a cable for connecting an electrocardiograph instrument to limbs electrodes and chest electrodes placed on the body of a patient, comprising a multiple core strap formed by a number of single core leads which are flexible and each being provided with a screen and arranged in a coplanar way adjacent to each other in substantial mutual contact and interconnected by at least one longitudinal continuous web of the same plastic material as that forming an external insulating sheath of the leads, this strap being provided at one end with a terminal with a connector in a housing for removable connection to the corresponding socket of the electrocardiograph, means of protection of the instrument, such as voltage dischargers, being incorporated in the housing of the connector, while at the other end of the strap the individual leads are branched off from the strap and - having been previously cut to the required length - are provided at their free ends with means for rapid and removable connection with the electrodes, each lead being associated with an electric resistance for protection against excess voltages. A cable of this type is known from the document US-A- 4 353372. In this known cable, the individual leads are branched off one after the other from the strap or all together from the end of the strap, without reinforcing the branching points, and the means provided at the free ends of the branched off individual leads for connection with the electrodes are formed as pads. Document DE-A-3 346 866 discloses an ECG-multilead cable where clamps are used in branching off points for the leads but with quite different electrical connections proximally and distally and unscreened leads The invention aims to provide a connecting cable of the aforesaid type which is more economical, easier to use and more reliable than the known type of cable. The cable according to the invention is characterized by the combination of the following features: a) at an intermediate point the strap is incorporated in a first clamp, after which the individual leads for the limbs electrodes are branched off, b) at an end point of the remaining strap, this strap is incorporated in a second clamp, after which the individual leads for the chest electrodes are branched off, c) the means provided at the free ends of the individual leads for connection with the electrodes, are constituted of plugs, each provided with an incorporated electrical resistor. The characteristics of the improved cable in question, and the advantages derived from it, will be evident from the following description which refers to the figures on the single attached sheet of drawings, in which: Figure 1 is schematic plan view of the new connecting cable; Figure 2 shows a magnified partial view in transverse section along the line II-II in figure 1 of the multiple-core and multiple-screen strap forming the new connecting cable; and Figure 3 shows the terminal for connecting the new cable to the electrocardiograph, in longitudinal section along the line III-III in figure 1. With reference to figures 1 and 2 initially, it will be noted that the new connecting cable is provided with a number of electrical conductors which are adjacent, flexible, parallel, and normally equidistant from each other 2, each of which is provided with at least one first flexible insulating sheath 3, then a flexible screening braid 4 and at least one flexible outer covering 5. The conductors, the screening and the insulating sheaths are made from any suitable materials having high technological reliability, such that they impart to the leads a considerable degree of flexibility and considerable resistance to mechanical stresses and to chemical and physical attack in general. The external sheaths 5 of the various leads are spaced a short distance apart, substantially in mutual contact, and are interconnected in a coplanar way by continuous webs 105 of suitable thickness, of the same material as that of the said sheaths, such as to form a multiple-core strap 1, containing the desired number of individually screened leads. The strap 1, formed in this way, may be constructed by known methods of extrusion of the plastic material forming the sheaths 5 and the connections 105. The new cable uses a section of multiple-core strap 1 of predetermined length, comprising for example 10 individually screened leads, which is provided at one end with a connector 6 described subsequently, for removable connection to the electrocardiograph. At the point at which the branch connections to the electrodes for the upper and lower limbs of the patient are to branch off, said strap is enclosed in a small flat body 7, having the function of a clamp, formed for example by injection of a suitable plastic material, preferably of the same type as that forming the sheaths 5. The leads for connection to the limbs are adjacent to each other and may be located on the same side of the strap or, as in the present example, on both sides of said strap. The leads for connection to the limbs branching from the clamp 7, indicated by C1-C2 and C9-C10, are mutually separated by breaking the web 105 connecting them together and to the other six leads from C3 to C8 which form the section of strap 1' which leaves the clamp 7 and remain interconnected. At the point at which the individual connections for the precordial branches are to be taken off from the last section 1' of the strap, in other words for connection to the electrodes placed on the patient's chest, the strap is enclosed in a small flat body 8, having the function of a clamp, also formed by injection of suitable plastic material. Leads C3 to C8 which are branched from the clamp 8 are separated from each other by breaking the interconnecting web 105, whose consistency is such that no substantial trace of the web remains, also to give maximum free sliding of the external sheath 5 of the individual leads. The individual leads branched from the clamps 7 and 8 are cut to the necessary length and their free ends are connected to the plugs 9 for rapid and removable connection to the measurement electrodes attached to the patient's body. The connection to the plugs 9 shall be such that the necessary metallic continuity of the conductor 2 and of the screen 4 of each lead is ensured, and includes the connection of an electrical resistor of suitable value in series with each conductor, to limit the risk of excess voltages in the direction of the electrocardiograph, for example in combined use with pacemakers, defibrillators or other electrical medical equipment. The body 109 of each plug 9, which covers the electrical connections to the lead and the aforesaid electrical resistor, is preferably formed by injection of a suitable plastic material, the same as in the clamps 7 and 8, to prevent tampering with the plugs and to ensure a sealed connection between the sheath of the lead and the metal terminals of the plug. The composition of the terminal 6 for connection to the electrocardiograph will now be described, with reference to the detail in figure 3. This figure shows that this component comprises a printed-circuit base 10, provided at one end with points 11 for selective connection to the electrical conductors of the strap 1 and with one or more points 111 close to the points 11 and preferably external, for connection to the screening 4 of the leads constituting the strap, which have previously been bundled together. The voltage dischargers 12 are mounted on the intermediate part of the base 10, and the multiple-core connector 13 to be inserted into the electrocardiograph socket is connected electrically and mechanically to the other end of the said base. The base 10, together with the components 12, and already connected to the strap 1 and to the connector 13, is then placed in a small mould into which is injected epoxy resin 14 which rapidly solidifies and incorporates the parts described, including an end section of the strap 1 and part of the body of the connector 13 which is thus securely fixed to the base. This may make it possible to carry out only the electrical connection of the connector to the base 10 beforehand. The resin body 14 is then housed in another mould into which is injected the same plastic material as that which forms the clamps 7 and 8, to provide the terminal in question with a coating 15 of more suitable material which ensures a sealed connection between the metal part of the connector 13 and the sheaths 5 of the leads forming the strap 1. Like the plugs 9, the terminal 6 cannot be tampered with. It is to be understood that the terminal 6, with the connector 13, may have a plan different from the T shape illustrated in figure 1, and that the connector may be formed and oriented differently depending on the type of connection used in the electrocardiograph. The simplicity of construction, the considerable economy and the considerable technological reliability of the connecting cable described are evident at this point, and are due to the continuity of the screening of the individual leads forming the strap used, permitting the elimination of the complex and expensive junction box used in known types of connecting cable. If appropriate terminals 9 and 13 are used, the new connecting cable is also completely sealed, a condition not present in known connecting cables, partly due to the internal accessibility of said junction box.

Claims: Cable for connecting an electrocardiograph instrument to limbs electrodes and chest electrodes placed on the body of a patient, comprising a multiple core strap (1) formed by a number of single core leads (C1-C10) which are flexible and each being provided with a screen (4) and arranged in a coplanar way adjacent to each other in substantial mutual contact and interconnected by at least one longitudinal continuous web (105) of the same plastic material as that forming an external insulating sheath (5) of the leads, this strap (1) being provided at one end with a terminal (6) with a connector (13) in a housing for removable connection to the corresponding socket of the electrocardiograph, means of protection of the instrument, such as voltage dischargers (12), being incorporated in the housing (15) of the connector (13), while at the other end of the strap (1) the individual leads (C1-C10) are branched off from the strap (1) and - having been previously cut to the required length - are provided at their free ends with means for rapid and removable connection with the electrodes, each lead (C1-C10) being associated with an electric resistance for protection against excess voltages, characterized by the combination of the following features: a) at an intermediate point the strap (1) is incorporated in a first clamp (7), after which the individual leads (C1, C2, C9, C10) for the limbs electrodes are branched off, b) at an end point of the remaining strap (1'), this strap (1') is incorporated in a second clamp (8), after which the individual leads (C3-C8) for the chest electrodes are branched off, c) the means provided at the free ends of the individual leads (C1-C10) for connection with the electrodes, are constituted of plugs (9), each provided with an incorporated electrical resistor. Cable according to claim 1, characterized in that the individual leads (C1, C2, C9, C10) for the limbs electrodes are branched off for one half on one side and for the other half on the other side of the strap (1). Cable according to claim 1, characterized in that all the individual leads (C1, C2, C9, C10) for the limbs electrodes are branched off on the same side of the strap (1). Cable according to claim 1, characterized in that both clamps (7, 8) are formed by injection of the same type of plastic material as that forming the external insulating sheath (5) of the leads. Cable according to claim 1, characterized in that the bodies (109) of the plugs (9) at the free ends of the individual leads are formed by injection of the same type of plastic material as that forming the external insulating sheath (5) of the leads.

Inventors: ZINI ROBERTO, ZINI, ROBERTO
Applicants: MORTARA RANGONI EUROP S R L, MORTARA RANGONI EUROPE S.R.L.
Application year: 1991
Main classification: A61B5
IPC codes: H01B7, A61B5, H01B11