fig1 shows the assembled structure of self - adjusting headgear appliance 100 and fig2 shows an exploded view of appliance 100 . in this embodiment , the appliance comprises seven receptors : three frontal receptors 1 , two central receptors 2 and two mastoid receptors 3 ( one mastoid receptor being mounted behind each of the patient &# 39 ; s ears ). in the preferred embodiment , the receptors are positioned on the appliance so that , when secured on the patient &# 39 ; s head , the frontal receptors 1 are mounted at sites fp1 , fp2 , fpz &# 39 ;, the central receptors 2 are mounted at sites cz and pz , and the mastoid receptors 3 are mounted at sites a1 and a2 , where these alphanumeric designators correspond to predetermined anatomical positions defined by the international 10 - 20 system . in the preferred embodiment frontal receptors 1 and mastoid receptors 3 are gold - or silver - composition coated type receptors . central receptors 2 consisting of gold - or silver - composition coated type electrodes are possible , as shown in fig1 and 2 . however , in the preferred embodiment , the central receptors 2 are typically reservoir type electrodes , as described further below and shown in fig4 . in the preferred embodiment , each frontal receptor 1 , central receptor 2 , and mastoid receptor 3 is affixed to strap 9 . strap 9 comprises a central section 10 and two mastoid sections 11 , as shown in fig1 and 2 . strap may be comprised of polyethylene terephthalate (&# 34 ; pet &# 34 ;) in the preferred embodiment , although other polymer sheet stock capable of carrying circuitry may be utilized . as shown in fig1 and 2 , each frontal receptor 1 , central receptor 2 , and mastoid receptor 3 has a distinct electrical connection to quick - connect plug 4 . in the preferred embodiment , the distinct electrical connection between each receptor and quick - connect plug 4 is provided by a circuit 8 inked on strap 9 . alternatively , this electrical connection may be provided by metallic wire or ribbon ( not shown ) of a type and size compatible with the amount of electrical current flowing and the resistance inherent in the selected material . quick - connect plug 4 is a multi - pin connector that corresponds matingly with a quick - connect plug on the patient interface cable hooking to the monitoring console ( not shown ). in the preferred embodiment , frontal receptors 1 and mastoid receptors 3 are secured to the patient &# 39 ; s head using adhesive patches 12 , as shown in fig1 and 2 . the three frontal receptors 1 are held by a single adhesive foam patch 12 , as shown in fig1 and 2 , which simplifies the task of positioning frontal receptors 1 at the desired sites fp1 , fp2 , and fpz &# 39 ;. adhesive foam patches 12 securing mastoid receptors 3 are of a modified half - moon shape to assist the clinician or anesthesiologist in placing these receptors at sites a1 and a2 behind the patient &# 39 ; s ears . the preferred embodiment uses adhesive patches 12 made from adhesive foam to secure frontal receptors 1 and mastoid receptors 3 to the patient . alternatively , adhesive patches 12 may be constructed of any commonly - known flexible material and attached using any commonly - known biocompatible adhesive that allows adhesive patch 12 to mold to the contours of the patient &# 39 ; s head at the intended attachment sites but is of a sufficiently rigid form to maintain the receptor flat against the patient &# 39 ; s head in its corresponding anatomically - precise site for durations of up to eight hours while preventing twisting , creeping or separation . the sticky surface of each adhesive patch 12 is sealed with a release liner 13 which is removed before mounting the receptor at the appropriate site . in the preferred embodiment , adjustment of the appliance to accommodate different head shapes and sizes is provided by self - adjusting elastic coils 14 located on the mastoid sections 11 of strap 9 , as shown in fig1 and 2 . fig3 shows front and side views of a typical self - adjusting elastic coil 14 . self - adjusting elastic coils 14 are formed integrally on mastoid sections 11 of strap 9 . the self adjusting elastic coils 14 may be fabricated using thermoforming or cold forming manufacturing techniques . a portion of strap 9 is woundtightly to form this embodiment such that it acquires a permanent &# 34 ; set &# 34 ; in its coiled configuration . the mechanical properties of the material allow self adjusting strap 14 to behave in an elastic manner when a tension force is applied to pull the coil open . since self - adjusting elastic coil 14 is a continuous coil with no creases , an electrical circuit ( conductive circuit ) will maintain continuity through the coiled section . the elastic coil generates tension , takes up slack , and maintains excess material in a relatively small , confined area . the self - adjusting , constant tension characteristic of the coil ensures that the appliance will fit snugly on and nearly flush to the patient &# 39 ; s head . this reduces the possibility that anything will be caught on the appliance during a surgical procedure or during invasive procedures such as intubation . self - adjusting elastic coil 14 is integral with both the primary structural component of the appliance and the media used for current / signal transmission ( conductive circuit 3 ), and functions simultaneously as the elastic member in the appliance . alternatively , self - adjusting elastic performance may be achieved by attaching rubber bands ( not shown ) in notches ( also not shown ) formed in the sides of the strap 9 adjacent to the coil when rolled up . by forming self - adjusting elastic coils 14 integrally with strap 9 , the invention is simplified by reducing the number of components required to achieve the required functionality and performance . this simplicity reduces manufacturing costs and makes the appliance much easier for the clinician to use . other traditional means of adjusting the length of the mastoid sections 11 of strap 9 are possible , such as elastic inserts , but are much less desirable because wires or other means for carrying the electrical current or signal become separate components complicating manufacturing and use while increasing cost of the appliance . in the preferred embodiment , electrical contact with the patient is maintained by a conductive , electrolytic gel . as shown in fig2 gel 22 is retained in frontal receptor 1 and mastoid receptor 3 locations by an open - cell sponge 15 . fig1 and 2 show central receptor locations utilizing typically hemispherical reservoirs 16 with pressure openable slit flat surfaces on the side adjacent to the patient for holding gel 22 in the two scalp positions ( serviced by central receptors 2 ). pressing on the reservoir will deploy the gel to make contact with the patient &# 39 ; s skin . an embodiment employing braille tip electrodes 17 in fig4 is preferred because it may enhance performance of central receptors 2 which must operate in an environment where hair is typically present . braille tip electrodes 17 in fig4 use a conductive sensor element that has protuberances 18 molded into it . protuberances 18 enable braille tip electrodes 17 to reach the skin through the hair follicles . since protuberances 18 are conductive , braille tip electrodes 17 allow deployment of the sensor surface through the hair to the skin . braille tip electrodes 17 have perforations 20 that enable conductive gel to be deployed from attached reservoir 16 through the hair onto the skin . reservoir 16 holds a substantial volume of conductive gel 22 which allows braille tip electrode 17 to wet out the hair follicles and skin in the area between the skin and protuberances 18 , thereby ensuring adequate signal quality . adhesive patches 12 , open cell sponges 15 , and reservoirs 16 shown in fig2 and reservoirs 16 shown with braille tip electrodes 17 shown in fig4 are secured to strap 9 using adhesive 21 . the appliance is attached to the patient &# 39 ; s head quickly and easily . the clinician would first locate fpz &# 39 ; and mount frontal receptors 1 by removing release liner 13 from adhesive patch 12 . the clinician would next locate a1 and a2 and mount mastoid receptors 3 by removing release liners 13 from each moon - shaped adhesive patch 12 . central receptors 2 would be positioned automatically through action of the self - adjusting elastic coils 14 . the clinician would then press reservoirs 16 to eject connective gel onto the patient &# 39 ; s scalp . to complete the set up , electrical connection to the monitoring unit would be effected by snapping the patient interface cable into quick connect plug 4 .
this invention defines a system for monitoring the brain activity of a human patient in order to monitor a patient &# 39 ; s brain electrical activity . the system uses a plurality of receptors which are mounted in predetermined anatomical positions on the patient &# 39 ; s head . the receptors are secured by adhesive foam patches . the appliance fits snugly to the head with the aid of self - adjusting strap that carry imbedded electrical circuitry for the receptors . electrical connectivity in locations where scalp hair is most likely to be present is improved by the use of braille - tip electrodes fitted with large gel reservoirs .