Patient temperature response control system and method

This application claims priority to U.S. Patent Provisional Application Ser. No. 60/988,706, filed Nov. 16, 2007, entitled “PATIENT TEMPERATURE RESPONSE CONTROL SYSTEM AND METHOD”, the entirety of which is hereby incorporated by reference.

The present invention relates to the field of induced hypothermia, and in particular, to a system and method that facilitates the control of patient shivering discomfort associated with induced hypothermia therapy.

Hypothermia is a condition in which body temperature is at a level lower than normal body temperature. Therapeutic induced mild-moderate hypothermia can be beneficial for people suffering stroke, myocardial infarction, cardiac arrest serious head trauma and other conditions involving reduced blood supply. One method for lowering body temperature is to insert a cooling device into an artery of the patient and to internally cool the patient\'s body by introducing a cooling fluid into the device. A non-invasive technique for lowering body temperature is to externally cool the exterior surface of the patient\'s body. Such exterior surface cooling could be achieved, for example, by direct contact with a cooling fluid, such as by immersing the patient\'s body in the cooling fluid or by directing the flow of the cooling fluid around the patient\'s body. The cooling fluid could be, for example, cool water or cool air. Another technique for external surface cooling is to apply a contact-cooling pad to the exterior surface of the patient and to circulate a cooling fluid, such as water or an aqueous solution, through the contact pad to cool the patient.

For therapeutic purposes, it is often desirable for the mild-moderate hypothermia to be induced very quickly. With endovascular cooling, heat is removed directly from blood flowing through blood vessels. Blood with reduced temperature moves through blood vessels to cool other parts of the body. With exterior surface cooling, heat is removed across the patient\'s skin. Cooling of the skin increases conduction of heat from deeper within the body, thereby cooling internal body tissue. Blood moving through blood vessels in a cooled portion of the body is also cooled, and distribution of that cooled blood to other parts of the body thereby contributes to cooling other parts of the body.

Quick inducement of hypothermia requires that the patient\'s body temperature be rapidly reduced to the desired level, and involves a high rate of transfer of heat from the body. Impediments to inducing hypothermia include the patient\'s thermoregulatory responses to cooling. Shivering is a common thermoregulatory response that, in some cases, can increase body heat production to as much as 600% above basal levels. Anti-shivering drugs, and particularly meperidine, have been administered prior to or during active cooling to help suppress the shivering response. Such pharmacological treatment to suppress shivering is often successful, resulting in more rapid lowering of the patient\'s body temperature to more quickly induce a desired degree of hypothermia, reducing patient tiring attendant to shivering, and also reducing patient discomfort associated with shivering.

In view of the foregoing, one objective of the present invention is to facilitate control over, and thereby reduce, patient shivering (e.g. in response to induced hypothermia).

A related objective of the present invention is to facilitate a reduction in patient shivering, and attendant patient heat production, patient tiring and patient discomfort(e.g. in induced hypothermia procedures) via a system and method that provide an output to facilitate anti-shivering response by medical personnel and that otherwise exhibit user-friendly functionalities.

Yet another objective is to facilitate a reduction in patient shivering (e.g. during induced hypothermia procedures) in a manner that enhances the efficiency of medical personnel in the performance of thermotherapy related activities.

One or more of the above objectives and additional advantages may be realized in a medical apparatus that includes a monitoring device for monitoring patient shivering or at least one physiological response of a patient to a change in the temperature of the patient and to provide a monitoring signal responsive thereto. The inventive apparatus may further include an output device for providing an output to a user responsive to the monitoring signal. In this regard, the output may be indicative of at least one measure of a physiological response, such as a magnitude, degree or progressive stage of shivering and/or information regarding potential response treatment option(s). By way of example, a visual and/or auditory output may be provided to a user that indicates that a predetermined level or stage of shivering has been detected and/or other information that may be useful in addressing a detected patient shivering condition.

In one aspect, the medical apparatus may further comprise at least one of an energy storage device and a wireless energy conversion device, interconnected to the monitoring device, for powering the monitoring device. In one approach, a wireless signal receiver and rectifier arrangement may be employed for receiving a wireless signal and transducing electrical energy therefrom to power the monitoring device. In conjunction with such approach, a wireless signal transmitter may be employed for transmitting a wireless signal corresponding with the monitoring signal. Alternatively, a transceiver may be employed for both receiving a wireless signal and transmitting a wireless signal corresponding with the monitoring signal.

In another approach, a battery may be employed as an energy storage device for powering the monitoring device. In conjunction with such approach, the battery may be interconnected with a transmitter for transmission of a wireless signal corresponding with the monitoring signal. Further, when a rechargeable battery is employed, a wireless signal receiver and rectifier may be included to transduce electrical energy from a wireless charging signal for recharging the rechargeable battery.

In conjunction with either of the above-noted approaches, an energy storage device and/or wireless energy conversion device may be interconnected to a monitoring device for co-movement therewith. More particularly, such components may be directly connected or interconnected to a common support member for co-movement, free from hardwire or other physical interconnections with a power source.

In a related aspect, the monitoring device may be non-invasive. In turn, use of the monitoring device may be initiated without compounding patient anxiety, patient tiring or patient discomfort otherwise attendant to the use of invasive devices.

In a further related aspect, the monitoring device may be provided to be selectively interconnectable to and disconnectable from a patient. When connected, the monitoring device may be maintainable in fixed relation to a given location on a patient. By way of example, the monitoring device may be interconnectable to a patient via a hook and loop fastener arrangement, a peel and stick adhesive surface arrangement or other like techniques.

In one approach, the monitoring device may comprise at least one motion sensor, e.g. an accelerometer selectively interconnectable/disconnectable to a patient, e.g. adhesively connectable to a patient\'s jaw (e.g. the masseter region). Such accelerometer(s) may be provided to measure acceleration in one and/or a plurality of orthogonal axes (e.g. one, two or three orthogonal axes).

In conjunction with such approach, a plurality of accelerometers may be interconnected to a patient at different locations to provide separate monitoring signals that may be employed together to facilitate the provision of an output indicative of a magnitude, degree or stage of patient shivering. For example, accelerometers may be separately interconnected to a patient\'s jaw (e.g. the masseter region), to a patient\'s chest (e.g. the pectoral region), to a patient\'s arm (e.g. the bicep region) and/or to a patient\'s leg (e.g. the quadriceps region), wherein corresponding monitoring signals from such accelerometers may be utilized to monitor a degree and for progressive stage of shivering. In this regard, each of the monitoring signals may comprise pre-determined signal portions (e.g. corresponding with a predetermined motion frequency range or ranges) whose presence and/or magnitude may be identified and utilized to generate a user output.

In another approach, the monitoring device may comprise a vasoconstriction measurement device for measuring blood flow at two to offset locations, e.g. at a fingertip and at corresponding forearm. In an additional approach, the monitoring device may comprise one or more electromyography (EMG) surface sensors for monitoring muscular electrical activity. In another approach, the monitoring device may comprise a pulse oximeter sensor for monitoring blood oxygen saturation levels of a patient. In yet a further approach, the monitoring device may comprise one or more capnography input sensors for concentration and/or partial pressure of carbon dioxide in patient respiratory gases.