Comprehensive pain assessment systems and methods

Abstract

Systems, devices, and methods are provided for simultaneous assessment of a subject's subjective and objective pain states. These include a dolorimeter arrangement for determining a subject's cutaneous pain tolerance level at any site on the body. In certain preferred embodiments, the dolorimeter is hand-held and utilizes a sonar distance-measuring device. In another aspect, the systems, devices, and methods of the current invention include platforms effective for implementing pain monitoring methods that include delivering pain questionnaires to patients over a period of time points. The platforms may harvest analgesic drug data from nurses attending the patients, and may provide simple statistical analysis of collected data useful both at the bedside and at central base-stations. The platforms may provide additional functions based on analysis of patient pain data. Preferred embodiments of the current invention combine the dolorimeter arrangement with the platforms for implementing pain monitoring methods.

Description

[0001] The invention described herein was funded, in part, by grant number R43NS34616 from the National Institutes of Health, under which the United States government has certain rights.TECHNICAL FIELD [0002] The present invention relates to neurological diagnostic tools including methods and devices for monitoring and managing patient pain. BACKGROUND ART [0003] Pain is the single most common symptom for which patients seek medical treatment and there is currently no objective method available for its measurement. Present methods of quantifying “pain” are little more than lexicons for its verbal description or biomechanical methods for measuring the restriction of a particular range of motion or activities of daily living associated with the pain. Some psychometric methods attempt to quantify the personality or cognitive distortions from which the pain patient suffers. In no case, however, do these methods reveal the covert and subjective sensory perception that is the pain experie...

AI Technical Summary

Benefits of technology

[0031] The present invention fulfills the need for a non-contact, radiant heat beam dolorimeter that provides a quantitative, objective measure of the pain tolerance level, is portable and allows for automatic data acquisition. These features of the present invention allow for its use as a cost-effective diagnostic tool in the general practitioner's office, thereby allowing for earlier assessment of neurological abnormalities than is possible with currently available pain measurement devices. The present invention allows for chronic pain diagnosis, the diagnosis of subtle sensory abnormalities, and pain measurement quality assurance. The present invention is currently alone in its ability to address both the clinical and commercial needs in quantitative pain measurement.

[0033] The present invention provides, as one embodiment of the invention, an improved dolorimeter which comprises a non-contact heat projector, set inside a housing assembly, for delivering a radiant heat stimulus, to cause pain in the subject; a targeting device, attached to the heat source housing assembly, for accurately positioning the heat projector for stimulus delivery; a thermopile, also attached to the heat source housing assembly, for detecting movement in response to the stimulus that indicates the subject has reached the pain tolerance level; and computer connections to the non-contact heat projector, the targeting device and the thermopile allow the computer to control the output of the heat projector and the targeting device, and also allow automatic data acquisition from the thermopile as to movement by the subject, thereby allowing the invention to be operated by a single person.

[0035] Additionally, in accordance with an embodiment of the present invention, the computer allows for interfacing between the computer and the subject, as well as between the computer and the computer operator, to allow for input by the subject and / or the operator. Moreover, in accordance with an embodiment of the present invention, the computer automatically acquires and records input from the interface between the subject and the computer, the interface between the computer and the computer operator, thereby facilitating the invention's operability by a single person.

[0039] a non-contact heat projector, set inside a housing assembly, for delivering a radiant heat stimulus, to cause pain in the subject; a targeting device, attached to the heat source housing assembly, for accurately positioning the heat projector for stimulus delivery; a thermopile, also attached to the heat source housing assembly, for detecting movement in response to the stimulus that indicates the subject has reached the pain tolerance level; and computer connections to the non-contact heat projector, the targeting device and the thermopile that allow the computer to control the output of the heat projector and the targeting device, and also allows automatic data acquisition from the thermopile as to movement by the subject, thereby allowing the apparatus to be operated by a single person. Additionally, in accordance with an embodiment of the present invention, the computer allows for interfacing between the computer and the subject, as well as between the computer and the computer operator, to allow for input by the subject and / or the operator. Moreover, in accordance with an embodiment of the present invention, the computer automatically acquires and records input from the interface between the subject and the computer, the interface between the computer and the computer operator, thereby facilitating the apparatus' operability by a single person.

[0046] In a preferred embodiment of this aspect of the invention, the distance sensor is a sonar ranging sensor. In another preferred embodiment, the automatic regulation of the projection of electromagnetic radiation provides a controlled effect at the target site when target-site distance changes within an effective control range. In another preferred embodiment, the electromagnetic radiation comprises infrared radiation and the distance sensor is a non-infrared laser.

[0056] In another aspect, the current invention provides methods and interface platforms effective for implementing pain monitoring methods for delivering pain questionnaires to patients at periodic, preferably regular (time settable), intervals. The methods and interface platforms may harvest analgesic drug data from nurses attending the patients, and may provide simple statistical analysis of collected data useful both at the bedside and at central base-stations. The methods and interface platforms may provide additional functions based on analysis of patient pain data. The devices and methods developed will greatly improve responsive pain therapy in pain-suffering patients and will additionally provide a centralized documentation method that will meet JCAHO guidelines.

Problems solved by technology

Pain is the single most common symptom for which patients seek medical treatment and there is currently no objective method available for its measurement.

The inappropriate desire for opiate drugs probably accounts for a significant fraction of pain therapy prescription drug demand.

Yet absent any objective method of establishing the existence of “pain”, the physician has no objective standards by which to prohibit such demand, and frequently feels ethically bound to take claims of pain at face value, or risk accusation of ineffective care and inhumane treatment.

For example, patient complaints of subjective numbness are often not detectable on clinical examination because present diagnostic methods are not sensitive enough to detect the early stage sensory impairments of such neurological disorders as nerve root entrapment or peripheral neuropathy.

As a result, patients with these types of neurological disorders cannot be diagnosed until the disorder progresses to a detectable level.

Basic psychophysical methods for the estimation of pain sensibility have a long history of questionable clinical relevance.

No studies have been able to demonstrate a relationship between pain threshold and the underlying pain state; in fact, pain threshold measurement procedures are unable to quantitatively demonstrate analgesic states engendered by clinically proven drugs as, for example, morphine (for review, see Chapman et al.

Furthermore, the method suffers from major disadvantages when transferred to the clinical situation where the test subject, who may suffer excruciating pain of endogenous pathological origin, is less able to attend to the minor sensory nuances of the pain threshold.

Tolerance methods using these techniques, unlike threshold methods, also evoke some not inconsiderable anxiety and apprehension on the part of the subject, which may resemble the anxiety of the pain-suffering patient.

However, studies have shown that tactile stimulation interferes with that aspect of cutaneous tolerance limit responsive to internal pain interference and thus methods that utilize a contact stimulus invalidate pain tolerance level results.

Therefore, this apparatus cannot be used to accurately measure pain tolerance.

However, most radiant heat pain stimulators have been designed to measure the pain threshold level and thus are prone to the disadvantages inherent in such measurement.

Thus, pain tolerance results obtained with the instrument are invalid.

The concept prototype was a nonportable, electromechanical device that did not allow for automatic data acquisition.

Unfortunately, available sensor response characteristics are largely inadequate to this task.

Thus, should a temperature sensor within the target be used to feedback control, for example, a motor-drive positioning mechanism on which a radiant heat projector (emitter) is mounted, whereby feedback from the sensor is used to control projector position, either toward or away from the target, it is found that accurate, rapid and responsive positioning of the emitter by the motor drive cannot be achieved because the sensor response time is invariably too slow, having too much inertia or resistance to change.

Verbal descriptor scales are commonly employed for pain assessment by asking the patient to rate their present pain on a numerical rating scale from one to one hundred or some other number: for instance, the NRS-101 asks the patient to scale their pain between one and a hundred and one but verbal enquiry has the serious disadvantage that the questioner (nurse or doctor) inevitably conveys expectation by voice, tone, facial expression, and demeanor, which will inevitably influence the patient's response.

However, when used to ask the patient to rate their present degree of pain without regard to any earlier response they may have made, this property of category scales proves somewhat of a disadvantage—since it is hoped in this situation that the patient's present response will be uninfluenced by prior responses.

These numbers are of course completely arbitrary in quantity though not in rank order, and hence parametric statistics cannot be used to compare scores.

The software driving this accessory is inherent to the thermode program and cannot in its present form be modified to stand alone as a patient assessment tool.

The Medoc device is hardware limited, in that it administers only one PQ test (the COPAS), and only in conjunction with the sensory testing protocol, and only by employing the ‘slide switch’ interface.

The BPM device is likewise by design and construction limited to its present purpose and takes several minutes to complete all the questionnaire forms.

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