Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
2000-10-11
2003-01-21
Fox, John (Department: 3753)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C165S046000
Reexamination Certificate
active
06508831
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns a system and method for thermoregulations of a living body. The system and method of the invention may be applied to both humans and animals.
BACKGROUND OF THE INVENTION AND PRIOR ART
A living body can maintain a normal body temperature, which in humans is about 36.5-37° C., under normal conditions. However, when subjected to extreme temperature conditions or to a variety of medical treatments, the body may not be able to properly regulate the body temperature. This is the case, for example: in individuals exposed to extreme temperatures; and in a variety of physiological disorders and medical conditions (e.g. general anesthesia) where the body loses its ability to properly regulate the body temperature.
Hypothermia is a reduction in body temperature which may result from exposure to a cold environment. Mild hypothermia in which body's core temperature (namely the temperature of internal organs and tissue within the body) is reduced by about 2° C. below the normal temperature, commonly occurs during and following surgery that is conducted under general anesthesia, as patients tend to lose body heat due to lowered metabolism and as a result of exposure of internal body organs or tissue, e.g. in an abdominal or thoracic cavity, to ambient air.
Hypothermia is experienced by more than 60% of patients after surgery. and in some surgical procedures, e.g. open heart surgery, hypothermia is experienced by more than 90% of adult patients.
Hypothermia can cause various severe physiological problems including cardiac morbidity, coagulopathy, impaired immune function, impaired wound healing, shivering, altered pharmaconnected properties of drugs, etc.
Hyperthermia, namely increase in body temperature above normal levels, may also cause various physiological disorders and if extreme, may be life threatening.
The clinical need to provide means for body temperature control has long been recognized.
MicroClimate Systems Inc., Stanford, Mich., U.S.A. markets a series of portable personal cooling systems (sold under the trademarks KOOLVEST, KOOLJACKET, KOOLBAND, KOOLPAID and others) which are intended for use by healthy persons who perform a physical activity in a hot environment (see Internet http://www.microclimate.com/prodline.html or http://www.microclimate.com/work.html). The system consists of a garment (it may be a vest, jacket, skull cap, a cervical collar, etc.) with tubing embedded therein in which water flows propelled by a battery-powered pump. Water passes through ice or through a cooling device before entering the tubing within the garment. The user can control the pump rate, the temperature, etc. A similar product line is also provided by Mallinckrodt Inc., St. Louis, Mo., U.S.A. (see the Internet at http://www/mallinckrodt.com/ccd) and others.
A similar system is disclosed in U.S. Pat. No. 4,807,447 (Macdonald et al). The unique feature of this system is that the person's breathing is used to operate the refrigerant compressor.
Various systems making use of garments, pads or blankets with heat transfer elements, e.g. conduits embedded therein, are disclosed in U.S. Pat. Nos. 3,738,367, 4,094,357, 4,094,367, 4,149,541, 4,844,072, 5,184,612 and 5,269,369. However, due to various physiological reasons, realized only in accordance with the present invention and which will be specified further below, none of the above systems provides adequate control of body temperature of the individuals in general, and of patients following surgery before undertaking general anesthesia in particular.
There is also a need for control of body temperature in veterinary medicine, particularly the control of body temperature during surgery under general anesthesia. Animals, and particularly small animals, occasionally die following surgery, owing to uncontrolled changes in body temperature.
GENERAL DESCRIPTION OF THE INVENTION
In the following, the term “core temperature” will be used to denote the temperature within the body, namely that of the internal organs and tissue. Core temperature is typically measured through the rectum (“rectal temperature measurement”) but may also he measured by inserting probes through a variety of other body cavities, e.g. mouth, nasal or ear temperature probes. The term “surface temperature” will be used to denote the temperature of the external body surface, (which may be that of the skin or, where the skin has been removed, e.g. in a bun injury, that of the most external layers). It should be noted that surface temperature may vary between different body portions. The surface temperature may be measured by a variety of temperature probes including, for example, an infrared sensor measuring infrared emission from a specific skin portion, probes attached to the skin such as a thermo-couple devices, thermistor, etc.
In accordance with the present invention, it has been realized that a major deficiency of prior art thermoregulatory devices is that these do not sufficiently reconcile the fact that the body is not a passive heat conductor but rather employs intrinsic dynamic physiological thermoregulation mechanisms which can change the heat transfer properties between the body's core and the periphery. For example, when exposed to a low temperature, there is a vasoconstriction of peripheral blood vessels, thus reducing blood flow to the periphery and thereby reducing heat transfer between the periphery and the body's core. In other situations there is vasodilatation resulting in increased blood flow to the periphery above normal levels thus bringing an increase in heat transfer rate between the body's core and the periphery.
In accordance with the invention, a system and method for the control of body temperature is provided. The system and method of the invention allows controlled cooling of body temperature, controlled heating, as well as regulating an individual's body temperature to remain at a desired set temperature. It is a unique feature of the invention that it takes into consideration the complexity of the heat transfer regiment from the skin to the body's core. This complexity is manifested by dynamic heat transfer properties, namely physiological changes which can alter the rate in which heat can be transferred between the skin and the body's core. Such heat transfer dynamics (HTD) may be determined by a variety of means, as will be illustrated further below.
In accordance with the invention there is provided a system for controlling an individual's body core temperature (BCT) comprising:
a heat exchanger for transferring heat to or removing heat from portions of the individual's body surface;
at least one BCT-sensing device for measuring the individual's actual BCT (aBCT) and emitting an aBCT data signal;
at least one sensing device for measuring a parameter indicative of the heat transfer dynamics (HTD) between the body surface and the body's core, and emitting an HTD data signal; and
a control module for receiving data signals from measuring devices. comprising the aBCT data signal and the HTD data signal, and for emitting a control signal for controlling heat exchange properties of said heat exchanger as a function of the data signals and the desired body core temperature (dBCT).
The heat exchange may either be provided with an internal heat or cold producing capability, e.g. including a Peltier effects modules, or the heat exchanger may be linked to at least one source of cold and/or hot fluid, which fluid then circulates between such source and the heat exchanges to transfer heat/cold between the exchanger and said source.
By another aspect, the present invention provides a method for controlling internal body temperature of an individual, comprising the following steps:
(a) defining a desired body core temperature (dBCT);
(b) providing a heat exchanger and bringing it into contact with at least a portion of the individual's external body surface, for heat transfer to or heat removal from the body portion;
(c) continuously measuring para
Fox John
Juneau Todd L.
M.T.R.E. Advanced Technology Ltd.
Nath Gary M.
Nath & Associates PLLC
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