Surgery – Diagnostic testing – Touch or pain response of skin
Reexamination Certificate
2002-03-28
2003-12-09
Marmor, II, Charles A. (Department: 3736)
Surgery
Diagnostic testing
Touch or pain response of skin
C600S549000, C600S555000
Reexamination Certificate
active
06659964
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to devices that use sonar to automatically control the delivery of electromagnetic radiation, including heat and light, to a target. In a preferred embodiment, the invention relates to sonar control of the delivery of radiant heat to the skin for the measurement of pain tolerance limits.
In applications where electromagnetic radiation (EMR) projected from an emitter is directed at a target, under conditions where distance may undesirably change between emitter and target, there is a need for automatic control processes that regulate the delivery rate of the EMR received at the target by adjusting the output of the emitter mechanism, the projector of heat or light or other EMR.
A true feedback mechanism would use a sensor, positioned at or within the target, to feedback-control either the power output or position—the emitter-target distance—of the emitter, thus ensuring that these characteristics of the emitter are rapidly and automatically adjusted to maintain target (and sensor) irradiation within set limits.
Unfortunately, available sensor response characteristics are largely inadequate to this task. Thus, should a temperature sensor within the target be used to feedback control a motor-drive positioning mechanism (for instance) on which a radiant heat projector (emitter) is mounted, and the feedback from the sensor be 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. The same is true of light and other forms of EMR.
When the emitter is employed as a sensory stimulator for testing human cutaneous sensibility, it is essential that the energy delivered to the skin be precisely controlled. Since delivered energy is a proportional function of the power of the emitter and the distance of the emitter to the skin target, both must be held constant to achieve adequate stimulus control. An earlier form of the computerized Heatbeam Dolorimeter (HBD) achieved this control by means of a precisely regulated power supply to the emitter, an infra-red (or heat or light) emitter, coupled with an articulated arm which allowed accurate positioning and an arrangement of intersecting visible lasers for guiding the precise positioning of the device at the correct emitter-target distance (Lipman J., U.S. Pat. No. 5,941,833).
Cutaneous sensory testing devices are employed in evaluating the state and the health of both the peripheral nervous system and the central nervous system and the central pain perceptual processes of the brain. Such testing devices employ some type of stimulus, either mechanical (tactile, pressure, vibration) thermal, electrical or of other modality, and assess the subject's ability to detect and respond to the stimulus. Of particular relevance to the present invention is the sensory examination of the human pain continuum by means of sensory testing devices. The cutaneous range of pain sensation of the skin, called the ‘pain sensibility range’ which is modality-specific, is bounded at the lower end of the stimulus intensity spectrum by the pain threshold, defined in terms of the stimulus intensity that is perceived as just noticeably painful by the subject. At the upper end of the pain sensibility range lies the pain tolerance limit, defined as the maximum possible pain stimulus intensity that the subject can tolerate. The pain tolerance limit has also been called the ‘reaction limit’ or ‘reaction threshold’ by some authors (Hardy J D, Wolff H G, Goodell H (1952).
Pain Sensations and Reactions
, Williams and Wilkins Co, Baltimore, 1952), because it is accompanied by reflexive aversive withdrawal of the subject from the stimulus.
Tactile methods, such as that described in Horch et al. (U.S. Pat. No. 5,022,407 Apparatus for Automated Tactile Testing), apply stimulator elements or electrodes held in close physical contact with the skin, which transmit vibration or pressure or pin prick stimuli. Thermal methods, of which a preferred embodiment of the present invention is a particular variation, transmit heat to the skin either through a peltier-type heating electrode in contact with the skin (see: Lautenbacher S & Rollman G B (1991)
Sex differences in responsiveness to painful and non-painful stimuli are dependent upon the stimulation method. Pain
53:255-264) or by radiant heat means using infra-red (see: Hardy J D, Wolff H G, Goodell H (1952),
Pain Sensations and Reactions
, Williams and Wilkins Co, Baltimore, 1952; and see: Lipman J J, Blumenkopf B & Parris W C V (1987)
Chronic pain assessment using heatbeam dolorimetry. Pain
30:59-67) or laser irradiation (Svensson et al., (1991) “
Comparison of four laser types for experimental pain stimulation on oral mucosa and hairy skin,” Lasers in Surgery and Medicine
11:313-324). Radiant heal methods of generating the stimulus to be used in pain threshold measurement may themselves be of either contact or non-contact application. Thus, one skin-contacting method proposed as suitable for forearm testing uses a horizontal glass plate on which the user rests their arm and through which a radiant beam of heat is directed (see Hargreaves et al., U.S. Pat. No. 5,025,796, Apparatus and Methods for determining in vivo response to thermal stimulation in an unrestrained subject). Likewise, a non-contact method (Hardy et al, ibid) has been used in pain threshold measurement at various body sites.
For measurement of the thresholds of cutaneous sensory pain-evoking modalities, of pressure, of mechanoceptive tactile sensibility, of heat pain and of electrical pain, the skin-contacting types of devices (here called “contact devices”) are both convenient to use and adequate in interpretation. In measurement of pain tolerance limits, however, devices which stimulate more than one modality (touch and heat, for instance) interfere with the sensory perception of each discrete sensory mode. Thus, pain tolerance to a heat (thermal) stimulus is altered by mechanoceptor (touch) stimulation. In measuring thermal pain tolerance, a skin-contacting method of heat delivery cannot be used, therefore and a pure unimodal non-contact stimulus is absolutely necessary. Prior inventions have addressed the problem of pressure (touch stimulation) interference on thermal pain sensibility by attempting to control and standardize the degree of pressure applied by the heat-delivering element (see Guillemin, U.S. Pat. No. 2,728,337) but the ideal solution to the problem of sensory interference is to be found in completely obviating the confounding non-thermal stimulus entirely.
The HBD device and method was developed to take advantage of this non-contact sensory requirement of pain tolerance measurement—the device stimulating the subject's skin by means of radiant heat and light without interfering mechanoceptor (touch sensation) stimulation. An earlier version has been described in which a radiant beam of heat and light, carefully calibrated and of constant power output and hence stimulus energy characteristics, employs two focused visible lasers to position the device at the correct distance from the skin, yet which may be carefully hand-held, and which employs a remote-sensing thermocouple to measure skin temperature during stimulus application (Lipman, U.S. Pat. No. 5,941,833 Heatbeam Dolorimeter for Pain and Sensory Evaluation). This Basic HBD device is mounted on a spring-loaded articulated support arm and is manually positioned by the operator at the appropriate distance from the various test sites around the body of the subject.
There remains a need however, fulfilled by the present invention, for an improved hand-held form of the above-described “basic Heatbeam Dolorimeter” device that can be conveniently employed in situations where examination room space is limited and an articulated positioning arm inconvenient. The ideal improvement would render the HBD capabl
Fitch Even Tabin & Flannery
Marmor, II Charles A.
Neuroscience Tool Works, Inc.
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