Abstract:
A mouth supported tongue/hard palate pressure sensor allows pressures to be measured between the tongue and hard palate in an environment that closely approximates the configuration of the tongue and mouth during natural swallowing to provide diagnosis and therapy for swallowing disorders.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to a medical instrument for measuring the strength of the tongue, and in particular, to an instrument for measuring contact pressures between the tongue and the hard palate for the diagnosis and treatment of swallowing disorders. 
     Tongue strength decreases as a person ages. A sufficient loss of tongue strength can lead to swallowing disorders, which in turn can cause physical disease in the individual as well as deprive the individual of the pleasure of eating. Nevertheless, research has shown that exercise of the tongue by pressing it against the hard palate for a number of repetitions each day at a given force level may increase tongue strength and may help improve the swallowing function. 
     A number of methods exist to measure tongue strength. Qualitatively the clinicians may have a patient press against a tongue depressor with his or her tongue. 
     The Tongue Force Measurement Systems (TOMS) developed by S. N. Robinovich, et al., provides a more accurate alternative. The TOMS device employs a custom built, dental-putty mouthpiece to align a user&#39;s tongue with a cantilevered beam. Force on the beam is detected by strain gauges sensing beam deflection. The TOMS device requires that the patient&#39;s mouth be open at about 40% of its maximum limit. A substantial portion of the TOM&#39;s mechanism extends outside the patient&#39;s mouth and is supported by an adjustable arm. 
     The National Institutes of Heath also produces a device to measure tongue strength, termed the APLSILT system. This device, which is commercially available from ACW Research Incorporated of Chatham, N.J., uses disposable tongue depressor mounted on a load cell held by a mechanism on an adjustable table. Only the tongue depressor is placed within the patient&#39;s mouth with the remaining portions of the mechanism being outside of the patient&#39;s mouth and supported on the table. 
     A Lingual Force Transducer, described in the paper  Force Production of the Genioglossus as a Function of Muscle Length in Normal Humans , by B. F. Sha, et al. Journal of Applied Physiology, 88, (5), 1678-84, includes a compact housing that may be inserted into the patient&#39;s mouth and which exposes a balloon on its leading surface. The balloon is connected to a pressure transducer and the device measures the force exerted by the tip of the tongue pressing in a direction out of the mouth, on the balloon. 
     The Iowa Oral Performance Instrument (IOPI), described in the article  Swallowing And Tongue Function Following Treatment For Oral And Oropharyngeal Cancer , by Lazarus, et al. 2000, Journal of Speech, Language and Hearing Research 43, 1011, is an air filled bulb, freely moveable within the mouth and attached to a hose that may be connected to a pressure transducer outside of the mouth. The transducer provides a light emitting diode display that indicates pressure on the bulb as a proportion of a manually set maximum to provide visual feedback to motivate the patient in an exercise program. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a device that allows placement of thin pressure sensors adjacent to the hard palate to measure tongue strength in an environment that closely matches the environment of normal swallowing, particularly with respect to mouth opening and tongue placement. The present invention also provides an in-mouth system that aligns itself against other mouth structure for repeatable and accurate measurements over the course of a diagnosis or exercise program. Thus, the invention is usable both by patients and healthy individuals who can be helped by an exercise program (henceforth collectively: “clients”). 
     Specifically, then, the present invention provides an apparatus for measuring the pressure exerted by a client&#39;s tongue against the hard palate. The invention includes a sensor support surface sized to fit closely adjacent to the hard palate and a mouth registration means attached to the sensor support and engaging the mouth structure to reproducibly locate the sensor support within the client&#39;s mouth. At least one electronic pressure sensor is positioned on a lower surface of the sensor support wholly within the mouth and facing the tongue to be activated thereby; and, an electronic annunciator communicates with the electronic pressure sensor to provide an indication to the client of the pressure measured by the electronic pressure sensor upon pressure by the tongue. 
     Thus, it is one object of the invention to provide a sensor system that allows the tongue pressure to be measured with the tongue positioned adjacent to the hard palate as during swallowing and that further allows the mouth to be closed to better approximate the natural mouth position during swallowing. 
     It is another object of the invention to provide these benefits in a system that presents an indication to the client for encouragement and feedback during training exercises. 
     Two electronic pressure sensors may be positioned on the lower surface of the support displaced along a midsagittal plane. 
     Thus, it is another object of the invention to provide finer resolution of measurement to the pressures between the tongue and hard palate such as may provide better insight of the swallowing process for a particular client. 
     The mouth registration means may include at least one surface engaging the client&#39;s teeth, for example, like the structure of a dental retainer, or as an interdental plate fitting between the client&#39;s teeth to be clamped thereby, allowing substantially full closure of the client&#39;s mouth for swallowing. 
     Thus it is another object of the invention to provide a simple registration means for the pressure sensors, such as allows reproducible measurement of tongue/hard palate pressures without the need for extensive mechanisms that must be independently supported or that limit the positioning of the client&#39;s head. 
     The mouth registration means may include either additionally or alternatively at least one surface engaging the client&#39;s hard palate, for example, a conformal mold of the client&#39;s hard palate. 
     Thus, it is another object of the invention to provide a registration means that helps to support the forces of tongue/hard palate interaction and that promotes accurate registration at the points of pressure measurement. 
     When the mouth registration surface is an interdental plate, it may be C-shaped and the sensor support may be a cantilevered arm attached to a point centered on the C of the interdental plate to extend upward from a plane of the C in the direction of curvature of the C. 
     It is thus another object of the invention to provide a simple structure for the support of the pressure sensors that may be readily adapted to a variety of different mouth sizes. The interdental plate may be a standard heat moldable mouthguard adjustable to conform to the client&#39;s teeth and the cantilevered arm may be adjustable through either bending or replacement to provide the proper depth and height for the client&#39;s mouth. 
     The electronic annunciator may communicate via conductive cables with the electronic pressure sensor where the cables include a connector for releasably separating the conductive cables into two portions. As mentioned, the sensor support may be removable from the mouth registration means. 
     Thus, it is another object of the invention to provide a sensor system that may be disassembled for easy cleaning of the mouth contacting parts. 
     The annunciator may be selected from the group consisting of a lamp, a tone generator, and a digital display. The digital display may provide a display of peak pressure, average pressure, or percentage of a predetermined peak pressure. 
     Thus is therefore another object of the invention to provide flexibility in communication of the pressure data to the client or the clinician according to the demands of different applications. 
     The annunciator may provide an indication of a pressure exceeding a predetermined threshold. In one embodiment, the predetermined threshold may be increased according to a predetermined schedule. 
     Thus, it is one object of the invention to provide a pressure sensing apparatus suitable for use in therapy in which a client is encouraged to provide a given pressure to the apparatus and that pressure is regularly increased in a training regime. 
     The foregoing objects and advantages may not apply to all embodiments of the invention and are not intended to define the scope of the invention, for which purpose claims are provided. In the following description, reference is made to the accompanying drawings, which form a part hereof, and in which there is shown by way of illustration, a preferred embodiment of the invention. Such embodiment also does not define the scope of the invention and reference must be made therefore to the claims for this purpose. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the present invention including a mouth-supported portion as attached by cabling to an external annunciator unit; 
     FIG. 2 is a midsagittal cross-section of a mouth cavity showing positioning of a sensor support of the mouth-supported portion of FIG. 1 within a client&#39;s mouth; 
     FIG. 3 is a perspective view from below of the sensor support of FIG. 2 showing location of the sensors and the retaining collar that may releasably engage a mouth registration means; 
     FIG. 4 is an electrical schematic of the sensors of FIG. 3 as attached to circuitry of the external annunciator unit for providing audible and visual feedback to the client; 
     FIG. 5 is an alternative schematic showing the sensors attached to a microcontroller within the external annunciator unit; and 
     FIG. 6 is a flow chart of the program of the microcontroller such as may provide an exercise regime to a client for improving tongue strength. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, the tongue/hard palate pressure sensor  10  of the present invention includes a mouth-supported portion  12  connected by electrical cable  14  to an external annunciator unit  16 . The mouth supported portion  12  includes a mouth registration structure  18  and a sensor support strip  20  both which may fit within a client&#39;s mouth when the client&#39;s mouth is substantially closed. 
     The mouth registration structure  18  conforms to the shape of a double mouth guard of a type used for the protection of teeth during athletic activity. Specifically, the mouth registration structure  18  provides for an upwardly opening top channel  22  and downwardly opening bottom channel  24  sharing a C-shaped interdental plate  27 , the latter which may be clamped between the client&#39;s teeth so that the top channel  22  may engage the upper teeth of the client and the bottom channel  24  may engage the lower teeth of the client. When in use, the C-shaped interdental plate  27  lies within a plane defined by the interface between opposed upper and lower teeth and curves backward along, and symmetrically about, the client&#39;s midsagittal plane  28 . The mouth guard may be the type manufactured by Everlast Worldwide, Inc of New York, N.Y. under the trade name of Everlast Double Mouthguard. 
     Referring also to FIG. 2, through the apex or front most portion of the C-shaped interdental plate  27 , a rectangular slot  26  may pass, providing an opening extending between the channels  22  and  24 . The sensor support strip  20  may extend rearward along the midsagittal plane  28  through the rectangular slot  26  and affixed to the mouth registration structure  18  at the rectangular slot  26 . A shank portion  30  of the sensor support strip  20  may connect to the electrical cable  14  pass between the client&#39;s incisors when the client&#39;s mouth is closed. A spoon portion  32  of the sensor support strip  20  may continue rearward into the client&#39;s mouth and upward to closely conform to the client&#39;s hard palate  34 . The sensor support strip  20  is thus attached in cantilevered fashion to the mouth registration structure  18  to be independently adjustable. 
     Referring now to FIGS. 1 and 3, the upper surface of the sensor support strip  20  includes a molded structure  40  conforming to the hard palate  34  to be well supported by the hard palate  34  and to provide additional registration for the sensor support strip  20 . The molded structure  40  may be fashioned from a cold cure dental acrylic of a type well known in the art. 
     Underlying the molded structure  40  is a stainless steel strip  42 , which may be wrapped with polyolefin heat shrink tubing (not shown). The molded structure  40  may be attached to the polyolefin on the top of the stainless steel strip  42  and two pressure sensors  46  and  48  may be attached directly to the underside of the spoon portion  32  of the stainless steel strip  42  using a thin film of silicone rubber adhesive (not shown). The pressure sensors  48  and  46  may be displaced along the midsagittal plane  28  to provide two points of measurement of tongue pressure, one near the front of the hard palate  34  and one near its center. The connecting wires  50  of the sensors  46  and  48  may be run along the underside of the stainless steel strip  42  toward the shank portion  30  and the front of the mouth and are, with the sensors  46  and  48 , ultimately covered with the heat shrink tubing. 
     Referring to FIGS. 1 and 3, the sensor support strip  20  may be attached to the rectangular slot  26  by means of a cold cured dental acrylic. Alternatively, the shank portion  30  of the sensor support strip  20  may include a molded collar  54  having detent  56  that releasably engage with complementary detent structure in the rectangular slot  26  to allow removal of the sensor support strip  20  from the rectangular slot  26  and thus from the mouth registration structure  18 . This simplifies cleaning and repair of the device and further allows the mixing of different standard sizes of sensor support strips  20  and mouth registration structures  18  to match different clients. The collar  54  may be designed to work with off the shelf double mouth guards, thus lowering the total cost of the device. 
     For the purpose of cleaning and storage, the electrical cable  14  may be broken by electrical connector  15  allowing it to be disconnected from the annunciator unit  16 . This also allows one annunciator unit  16  to be shared with multiple mouth-supported portions  12 . 
     Referring now to FIGS. 1 and 4, each of the pressure sensors  46  and  48  may be conductive, thick-film polymer sensors of a type commercially available under the tradename: FSR® Model 400 from Interlink Electronics of Camarillo, Calif. providing a change in electrical resistance under pressure as detected by interdigitated electrodes on one or both surfaces of a flat polymer disk. Alternative pressure sensors including those based on strain gauges, piezoelectric materials or mechanical switches may also be used. 
     Pressure sensors  46  and  48  are connected within the annunciator unit  16  to provide the upper leg of two resistive ladders, with pressure sensor  46  being in series with resistor  60  and sensor  48  being in series with resistor  62 . Resistors  60  and  62  are selected to provide the maximum dynamic range of voltage change at the junction of the resistance and the sensor consistent with the desired power dissipation. The upper and lower terminals of the resistive ladders are connected across a source of DC power supplied from a nine-volt battery (not shown). 
     The junction of resistor  60  and pressure sensor  46  is attached to the non-inverting input of operational amplifier  64  and the junction of resistor  62  and sensor  48  is attached to the non-inverting input of operational amplifier  66 . The inverting inputs of operational amplifiers of  64  and  66  are attached to a center tap of a potentiometer  68  whose other terminals are attached across the local voltage source. The operational amplifiers  64  and  66  are operated in open loop configuration to provide voltage comparators whose comparison threshold is determined by the potentiometer  68 . The control of the potentiometer  68  may be accessible to the client or clinician so that it may be adjusted to set the threshold of pressure required for the outputs of the operational amplifiers  64  and  66  to provide a high state voltage. 
     The outputs of the operational amplifier  64  and  66  are connected through an OR-gate formed by two diodes  70  to an audio transducer  72  to provide an audible indication when the set threshold pressure has been achieved or exceeded at either of pressure sensors  46  and  48 . 
     Alternatively, but not shown, two audio transducers  72  may be used having slightly different tones and attached individually to the outputs of operational amplifiers  64  and  66  to provide an indication both that the pressure has been exceeded and the location of the pressure. 
     Alternatively, the audio transducers  72  may be replaced or supplemented with a visual transducer such as an LED or other visual system. 
     The junction of resistor  60  and pressure sensor  46  may also be attached to a variable gain amplifier  74  while the junction of resistor  62  and sensor  48  may also be attached to variable gain amplifier  76 , each of whose outputs go to a multiplexed digital display  78  which provide a quantitative output indicating actual pressure applied to the pressure sensors  46  and  48 . The variability of the variable gain amplifiers  74  and  76  allows calibration of the digital display  78  so as to read in convenient units of pressure or arbitrary normalized units suitable for this purpose. 
     Alternatively, but not shown, two displays  78  may be used, one connected to each of the outputs of variable gain amplifier  74  and  76 . Digital displays  78  of this type are readily available from a number of commercial sources and include internal analog to digital converter and the necessary character generation circuitry. 
     The digital display  78  may work in conjunction with the audio transducer  72  to provide setting of the potentiometer  68 . A series of exercises may be performed by the client pressing upward against the sensors  46  and  48  with the client or clinician observing the digital display  78 . The potentiometer  68  may then be set to a desired training level based on observation of the digital display  78 . 
     Referring now to FIG. 5, it will be understood to those of ordinary skill in the art that the circuitry of FIG. 4 may be implemented in a variety of different ways using techniques well known in the art. One such embodiment may include the use of a microcontroller  80  having analog inputs  83  communicating with internal analog to digital converters for connecting directly to the junctions of pressure sensors  46  and resistor  60  and sensor  48  and resistor  62 , respectively. The microcontroller  80  may directly control the digital display  78  through binary output lines as well as with the audio transducer  72 . Such microcontrollers  80  are manufactured by the Microchip company of Chandler, Ariz. 
     Referring to FIG. 6, the microcontroller  80  may be programmed to execute a program  82  providing additional functions to the above device. At a first process block  84  of the program  82 , the microcontroller  80  receives data from the pressure sensors  46  and  48  for a series of trials during which the client presses upward with the tongue, toward the hard palate  34  to exert a peak pressure. The peak pressure may be simultaneously shown on digital display  78 . 
     At process block  84 , the peak pressure for each of these trials is stored in the on-board memory of the microcontroller  80  and at process block  86 , a maximum one of these pressures is selected. 
     At process block  88 , the maximum pressure is reduced by a predetermined percentage, preferably 80%, to become a pressure amount for subsequent exercises by the client. 
     At process block  90 , during a subsequent exercise session by the client, the microcontroller  80  receives new pressure data from the pressure sensors  46  and  48  and at process block  92 , the microcontroller provides feedback in the form of an audio signal through audio transducer  72  to the client when the target amount has been exceeded. At the same time, the microcontroller  80  may display a percentage of the target amount that has been achieved. 
     Upon the conclusion of the training session, as indicated by process block  94 , the target pressure is increased slightly for the next training session. Over many training sessions, the target pressure is increased to the maximum pressure. 
     The arithmetic capabilities of the microcontroller  80  allow the display  78  to provide a variety of different modes including display of peak pressure over a predetermined window of time, average pressure over a predetermined window, or percentage of a target pressure as may be desired by process block  92 . In addition, the microcontroller  80  may store data for later clinician review. The display  78  may be used to cue the client as to which steps in the exercise program are to be undertaken. 
     It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but that modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments also be included as come within the scope of the following claims.