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Measurement of autonomic functionRelated Patent Categories: Surgery, Diagnostic Testing, Structure Of Body-contacting Electrode Or Electrode Inserted In Body, Means For Attaching Electrode To Body, AdhesiveMeasurement of autonomic function description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20080091098, Measurement of autonomic function. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATION [0001] This application is based on provisional application Ser. No. 60/837,658 filed Aug. 15, 2006. FIELD OF THE INVENTION [0002] The invention relates to methods of detecting and quantifying nociception and pain, and devices and components related thereto. BACKGROUND OF THE INVENTION [0003] The autonomic nervous system (ANS) governs the functioning of numerous organs in the body of humans and other mammals. Yet there exists no quick, simple, inexpensive, or reliable test to measure the full range of autonomic function in an individual, nor its current state. [0004] The two major components of the ANS are the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS). Nerves from both usually innervate the organs they control. Thus organ performance is the result of the interplay of both PNS and SNS. A measure of either SNS or PNS is not very useful in assessing the condition of the subject. For example, a subject may have high PNS tone without being relaxed because its effects are being offset by high SNS tone. Heart rate, for example, is determined by interplay between PNS and SNS. Both nerves innervate and affect our hearts. When a subject's PNS vagal nerves to the heart are cut, its heart rate rises and remains elevated. [0005] A novel method is described herein to measure the moment-to-moment relative dominance of PNS tone (sometimes also referred to as vagal tone) and SNS tone. The method is inexpensive, easily understood, consistent, reliable, as well as simple and quick to administer. It is completely passive and requires no voltage to be administered to the subject, thus eliminating the possibility of side effects from the resultant current. It works well on both humans and animals. [0006] The method gives a distinctive, "signature" reading for subjects experiencing any moderate to severe pain that has lasted for more than a few minutes, both in humans and other mammals. Therefore, it provides a previously non-existent, objective description of pain. Currently, all pain is now measured by asking the subject questions about their pain (i.e., "On a scale of 0-10, how would you rate your pain?"). This is clearly subjective. Non-verbal patients cannot be evaluated by these methods. Thus health care providers are at a loss to measure pain in young children, advanced dementia adults, some stroke victims and intubated patients, as well as the rest of the animal kingdom. Prey species of animals (including horses and sheep) pose a particular challenge because they are genetically programmed to mask their pain so as not to become the primary target of a predator. Even expensive thoroughbred racehorses are often the subject of vigorous debate by their caretakers regarding their pain status. Furthermore, a reliable and consistent objective measure of pain would prove useful to doctors who suspect the patient is exaggerating or imagining his or her pain, as well as to insurers who suspect malingering. [0007] The method described herein works by recording a measurable physiological correlate of ANS changes, namely the difference in electrical potential between two sensors placed on the skin. Similar to the Tarchinoff voltage measure of electrophysiology, it differs by sensing between sites of similar instead of high to low sweat gland densities. Skin is innervated by nerves from both the SNS and PNS, which, respectively, increase and decrease physiological rates in tissue and organs throughout the body. These nerves are distributed relatively symmetrically throughout the body but are not always activated in a symmetrical manner. With pain, for example, persistent pain from anywhere in the body of moderate to severe intensity begins to raise blood pressure (BP). This activates the baroreceptors in the carotid sinus artery. They trigger an increase in PNS (vagal) tone in an attempt to stop the BP increase and restore homeostasis. In addition, this process triggers the release of endorphins, the body's own, natural opioids which provide partial pain relief. This process is part of what is known as Descending Nociceptive Inhibitory Control, or DNIC. This response is mediated primarily by the right cardiac vagal (PNS) nerve, not the left one. This nerve branches off and innervates other tissue along the way. The result is slightly slower physiology on the right side of the body. It has now been found that this includes the two-skin-site voltage difference effect. Accordingly, the voltage sensed on the right side of the body, with respect to the left, drops as PNS tone rises through increased activation of the right cardiac vagal nerve. PRIOR ART [0008] Most Galvanic Skin Reflex measurement has been done by sensing the Fere effect, so named after its discoverer. This is the change in the skin's ability to conduct electrical current due to sweat gland activity. The reason for this method has been due partly to the relative ease, reliability, and consistency of measurements. This is due to the relatively large applied voltages used to measure the Fere effect, in contrast to the small, natural, body voltages of the Tarchinoff aspect of the GSR. In the case of the present invention, the magnitude of the voltage difference between the right and left sites on the body, is often smaller than the offset voltages of sensors which have been standard in the industry. Data gathered with high offset sensors would lead to inconsistent measurements and the conclusion that there was no useful information to be obtained this way. The invention described herein overcomes these deficiencies of the prior art methods. [0009] Two posters have been presented at medical conferences showing anecdotal reports of such ANS shifts reflected in skin potential. (Ngeow, et al, Aug. 21-26, 2005), (D'Angelo, May 2006). This previous work did not use sensors which had been selected for their low offset potentials. The practitioners presenting these posters had been unaware of the role of offset potentials in these types of measurements, and it was not discussed in their posters. The form of sensor used to obtain the data presented in the posters has produced a wide and changing variety of offset potentials due to a combination of factors. One was a lack of consistency in manufacture. Still another was a lack of consistency in use. These sensors were of a cup style which required the examiner to fill the cups above the Ag/AgCl coated sensor surface to the brim of the cup with conductive gel. If the examiner fails to place the adhesive collar with its hole directly above the cup, part of the collar will cover some of the electrode gel, blocking its area of contact with the skin. This may produce a smaller signal coupled to the system load resistor. In addition, if the examiner fails to fill one of the cups completely to the brim, this may introduce a difference between the area of contact of the two recording electrodes that also may produce a smaller coupled signal. Occasionally, good readings can be taken, such as those selected for the posters, but they cannot be obtained consistently with the type of sensor methodolgy shown in the posters even with trained personnel in the time conscious environment of a clinical setting. The proposed method solves that by using pre-applied gel that has been spread evenly on each electrode during manufacture, producing much more consistent readings. [0010] The present low offset voltage sensors invention can be used to track the progress of an individual during a series of treatments or during healing, due to consistent readings obtained by minute and consistent offset potentials. This cannot be said of most other types of electrodes. [0011] Most prior work involving the use of measuring sensors on the skin in order to chart autonomic changes has been Galvanic Skin Resistance Work. This also uses electrodes on the hands, but the purpose and approach is of an entirely different type. In GSRes an external voltage is applied to the subject's skin through a pair of sensors and the OSRes unit measures the current. [0012] Levengood and Gedye in U.S. Pat. No. 6,347,238 utilize some of the same hardware as the disclosed invention but their method has great limitations. Levengood teaches electrodes against which the hand must be pressed neither of which is self-adhesive and both of which must be pressed against the hand or body by the physical force of tester or subject. Since the magnitude of the coupled resistance loaded signal is affected by the area of contact, even very slight variations in pressure produce artifacts, namely variations in the recording. If skin surface contact resistances of the sensor pair, in some manner, tap into a bulk, internal, electrical field gradient, a voltage polarity reversal may even be brought about by a difference in physical force being applied to the left versus right sensor. The self-adhesive sensor employed in the present invention eliminates this deficiency. Levengood's method is further limited by its use of solid metals. Virtually all solid metals form a "half-cell" potential when they are in contact with a saline solution such as the subject's perspiration. This well known electrochemical effect need not be further elucidated. The absolute and imbalance magnitudes of the half-cells for aluminum, the metal specified in Levengood, are amongst the largest for solid metals. This artifact can overshadow the small signals being sought in the two-sensor site voltage measure. At a minimum, it will affect the numeric reading of the site to site voltage. AgCl coated Ag sensors of the type employed in the present invention minimize this effect. Such low offset sensors are not taught by Levengood. [0013] Unlike prior art that deals primarily with the Fere effect and involves active addition of extraneous electrical current to the skin, the present invention, like Levengood, measures only the two site voltage measure. Leavengood does not teach the involvement of the ANS. Accordingly, the occasional false positive cannot be spotted. Occasionally a subject produces a positive reading despite being in moderate to severe pain. If ANS indictors such as Heart Rate and Diastolic Blood Pressure are over 95, the examiner can take into account that SNS tone is obviously extremely high at the moment and therefore the reading is unreliable. A chronic pain patient with pain of 7 on the 0-10 VAS scale could still produce a positive reading under these conditions. Thus the other cited prior art does not teach the disclosed method. None of the cited prior art deals with offset potentials of the sensors used. Without consideration of offset potentials, the weak two site voltage difference cannot be measured accurately. Even some commercial Ag/AgCl sensors possess offset potentials sufficient to seriously affect the voltage readings of the present method. However, by utilizing low offset potential electrodes (i.e. below 1.0 mV as in the disclosed system, (and the lower the offset potential the better) as described in more detail herein below, the voltage difference can be measured with consistent accuracy. Selected low offset potential sensors were not taught in the prior art. SUMMARY OF THE INVENTION [0014] The present invention is an article of manufacture and method for using same, comprising at least two electrodes or "sensors" having an offset potential of below about +/-1.0 mV; and a data gathering device connected to the sensors capable of measuring the voltage differential between the electrodes. The sensors preferably are AgCl coated Silver. [0015] It is an object of the invention to teach a device capable of measuring pain in a subject. [0016] It is also an object of the invention to detect changes in the ANS. [0017] It is a further object of the invention to teach a device capable of measuring pain that uses low offset potential sensors. [0018] It is another object of the invention to teach a device that senses voltage and does not pass a significant, exploratory current through the subject. [0019] It is yet another object of the invention to teach a pain measuring device that utilizes AgCl coated Ag sensors. Continue reading about Measurement of autonomic function... Full patent description for Measurement of autonomic function Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Measurement of autonomic function patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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