Surgery – Diagnostic testing – Detecting brain electric signal
Reexamination Certificate
2001-10-15
2004-11-30
Jones, Mary Beth (Department: 3736)
Surgery
Diagnostic testing
Detecting brain electric signal
C600S300000, C600S509000, C600S544000, C600S546000, C600S557000
Reexamination Certificate
active
06826426
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The field of the present invention relates to medical diagnostic tools. More particularly, the field of the present invention relates to systems and methods relating to measuring and reporting a subject's pain.
2. Background
Pain is an unpleasant sensation, ranging from slight discomfort to intense suffering. But because to a great extent pain is a subjective phenomenon, it has frequently defied objective, quantitative measurement. Traditionally, physicians have had to assess a patient's pain by relying on the patient's own description of it. But self-description is not only subjective by definition, it is often inaccurate, in part because it is difficult for subjects to precisely articulate their pain while in the midst of a pain experience.
Moreover, objective assessment of pain is all but impossible in situations where the patient is not fully communicative, such as when the patient is an infant, the patient is not fully conscious or coherent, or the patient is a non-human.
Today, uni-dimensional scales are used to quantify pain. These scales frequently employ verbal (mild, moderate, severe) and numerical (0-10) ratings. Today's caregivers also use multidimensional scales along with complex, pain diagnosis questionnaires designed to extract as much subjective information as possible from the subject (e.g. sensory, emotional and cognitive).
These pain quantification methods are used in a number of settings. Most commonly, physicians and other health care professionals apply these methods to diagnose and/or treat a patient. Physicians may also use these methods to track the progress of a patient's illness over time or to determine an amount of pain medication to prescribe to a patient. In other settings, these methods are used to test the efficacy of certain pain-relieving drugs and to establish standard dosages for them. Nonetheless, these methods often lead to inaccurate conclusions because of the subjective nature of the assessment inherent in them.
Logically, pain assessment plays a vital role in determining the amount of pain medication to give a patient. As a result, hospital staff and other health care providers also use visual clues to assess the intensity of a patient's pain and determine the amount of pain medication to provide. Under this visual assessment method, the caregiver will commonly use a visual analog scale (VAS), usually scored from 1 to 10, to rate a patient's pain intensity. In a typical scenario, the caregiver will consider different clues to score the patient's pain intensity, such as facial expressions and cardio-respiratory function, in addition to patient statements of satisfaction.
Notwithstanding the healthcare providers' diligence, studies have shown that professional caregivers usually give too much or too little pain medication to patients evaluated with these visual scoring methods. Importantly, a caregiver's failure to give enough pain medication may not only reduce a patient's quality of life, but may compromise a patient's ability to fight disease, cause or complicate physiological disorders, and even hasten death. On the other hand, caregivers that overmedicate patients can also cause harmful side effects, including, in extreme cases, patient respiratory arrest.
Some patients also intentionally misrepresent the existence or extent of their pain. These misrepresentations may stem from financial or fiduciary incentives (including a desire for disability payments or insurance damage settlements), chemical dependencies on pain medications, or other patient-perceived secondary benefits to obtaining pain medication. Regardless of the motivation, patient misrepresentation accounts for a significant portion of the demand for pain medication prescriptions. Yet, without any reliable basis for denying such prescriptions, physicians generally must assume that the claims are truthful, even when they may suspect a lack of sincerity. Otherwise, the caregiver may be accused of inhumane treatment. Conversely, other patients may underreport their pain, again for a variety of reasons.
Despite these inaccurate representations, hospitals and other healthcare givers often provide patients with a class of devices known as Patient Controlled Analgesia (PCA) devices. PCA devices employ a type of analgesia system that enables the patient, often in a post-operative setting, to self-administer pain medicine.
Commercial PCA devices include devices such as the Atom PCA Pump 500, APII, Deltec CADD-PCA 5800, Sabratek 6060 and the Verifuse. In a common form of PCA, the patient is provided with a mechanical apparatus comprised of a reservoir and a patient-operable pump. On patient demand, the pump dispenses incremental doses of pain medicine from the resevoir into the patient's intravenous (IV) system. The device may also comprise a lock-out interval feature that prevents patient remedication for a period of time so as to ensure against over-medication.
While caregivers using VAS methods cannot consistently provide the right amount of pain medication to patients, studies have likewise shown that a patient's own assessment of satisfaction, even when used in connection with a PCA device, does not reliably indicate when to deliver pain medication. One study shows that although patients may feel satisfied by a regimen of self-administered pain therapy, the majority of those same patients are self-treated below their individual subjective pain thresholds. Forst et. al., Archives of Orthopaedic and Trauma Surgery (Germany), v. 119, p. 267-270, (1999). Moreover, the act of self-medication itself has been found to be unimportant to the issue of patient satisfaction when the patient has sufficient pain relief through medication. Chumbley, et al., Anesthesia (England), v. 54 (4), p. 386-9 (1999).
The present PCA methods and systems also have other drawbacks. For example, they cannot be readily used, if at all, for infants, toddlers, certain spinal cord patients, and others who cannot operate the device or are unable to understand the instructions for controlling the PCA. Also, current PCA devices do not normalize people's responses, thereby making the subjective nature of pain self-assessment a factor in the operation of the PCA. Even in honest attempts to be objective, patients may rate the same subjective experience of pain differently. For example, one person may rate a certain subjective sensation of pain a “10” on the VAS scale whereas another person may rate the same or a similar subjective sensation of pain a “5” depending on a variety of psychological factors and life experiences. Thus, without a means to normalize patient self-assessment, PCA devices rely on subjective psychological factors as much as on the type of illness to determine how much pain medicine to provide.
Moreover, self-assessment may lead to inconsistent treatment between different patient types. For example, children who use PCA devices have been reported to frequently experience nausea and vomiting as a result of overdoses, as compared with adults. PCA devices also do not typically reduce the burden on caregivers because, in many cases, the caregivers must repeatedly instruct patients on how to use the PCA devices and monitor their use.
In contrast, previous efforts in pain research have attempted to identify physiological phenomena related to the subjective sensation of pain. Heart-rate, blood pressure, perspiration and skin conductance are some of the physiological phenomena that have been found to be affected by pain. But these physiological phenomena have also been found to be non-specific to pain and, in fact, have been used in other applications, such as polygraphy. Furthermore, these physiological phenomena tend to habituate quickly. Consequently, they are inadequate for objectively assessing pain.
U.S. Pat. No. 6,018,675 issued to Apkarian et al. discloses a pain measurement system based on comparative functional magnetic resonance imaging (MRI) of the brain of a subj
Lange Daniel H.
Lewinsky Reuven
Algodyne, Ltd.
Jones Mary Beth
Jones Day
Mallari Patricia C
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