This research involves the design of novel devices and development of new models to take advantage of a recently observed phenomenon capable of rapidly reducing body core temperatures. The research builds upon observations that arteriovenous anastomoses (AVAs) in glabrous skin become mechanically distended when a small negative pressure (about 40 mm Hg) is applied to the body. When negative pressure is utilized in conjunction with surface cooling of the skin, body core temperatures can be rapidly lowered due to increased blood flow rates between the skin and the body core.
Intellectual Merit: The intellectual focus of this project is to build a predictive model of heat transfer between the skin and body core via enhanced blood perfusion through distended AVAs. The model will be used to design devices and identify appropriate protocols for manipulation of human thermoregulatory function. Specifically, the complex AVA control mechanisms will be measured and characterized by way of human testing and the corresponding constitutive models will be incorporated into the Wissler thermoregulatory model.
Broader Impacts: The broader focus of the research is to develop a new technology that can rapidly reduce core temperature from hyperthermic (heat stress) states for industrial, military and athletic needs and from normothermia to hypothermic states for medical needs (therapeutic hypothermia). The research may also lead to new treatments of stroke, cardiac arrest and concussion. Outreach to local minority-serving high schools will be a key component of the activity. New educational materials will be developed in conjunction with the research and will be disseminated in the archival learning science and engineering education literature. Experimental and modeling outcomes of the research will also be incorporated into supplemental learning materials of a new biotransport text.
This project deals with the invention, development, and application of multiple new technologies for using body surface heat transfer to provide temperature-based therapies to patients. A theme common to all of the therapies is that they are safe and easy to administer, based on simple devices that operate via totally noninvasive processes, and that take advantage of novel advanced understandings of the physiological response to heat and cold that are a core outcome of this research. There are two classes of technologies, both of which incorporate the application of controlled heat transfer processes to the surface of the skin. One technology is used to regulate the core temperature of a human, either to lower it for patients who have suffered an event such as a stroke, heart attack, or concussion, that causes major organ ischemia, especially to the brain, or to raise it for patients who have become hypothermic during surgery. The second technology is used to apply cooling and/or heating to the surface of the skin to treat soft tissue injuries, while avoiding the potential negative side effects of exposure to deep levels of ischemia for a prolonged time. 1. Therapeutic core temperature management: This technology is based on a novel two step procedure that takes advantage of the body’s normal and powerful capability to selectively move heat between the surface and the core via high rates of circulation of blood from areas of glabrous skin (primarily palms of hands and soles of feet). Control of glabrous skin blood flow (GSBF) is critical to normal thermoregulatory function, especially for conditions of hot and cold thermal stress. GSBF embodies a much higher level of thermal performance than is available in other areas of the body’s surface, and our technology takes advantage of this phenomenon. The challenge is to drive GSBF to a high level when it is not already established by existing thermal stress so that heat exchangers may be applied to the palmar and plantar surfaces to extract or add heat to blood before it is circulated back to the core. Thus, the key first step to our technology is to trigger GSBF to a high level on demand. We may apply the trigger via various alternative stimulation methods applied to key control tissues that are responsive to thermal or electrical inputs and that can reduce vasoconstriction of GSBF. The second step is to apply a surface heat exchanger to palmar and plantar skin to alter the temperature of the GSBF before it returns to the core. Although the principle of this technology is mechanically modest, its successful utilization requires insightful coordination with physiological function, which turns out to be a challenging task. With support of this grant we have conducted hundreds of human trials to characterize the physiological trigger phenomenon and its domains of efficacy. We are setting up the initial clinical trials for this technology to evaluate both the trigger and heat exchange steps on a population of acutely ill patients under the supervision of our neurosurgical collaborator. Our first archival paper that presents the trigger data is now undergoing final revision for submission. We believe it will present physiological data and information that heretofore has not been available in the scientific literature. A second paper that presents data acquired for experiments that combine the trigger and heat transfer steps is in preparation. Six patent applications have been filed. 2. Surface cooling of injured soft tissue: The application of cold to the skin surface has been used for thousands of years to reduce pain, swelling, and inflammation associated with soft tissue injuries. In recent decades this therapeutic modality has been embodied into devices consisting primarily of an insulated chest filled with ice and water and with an immersion pump to deliver cold water through a flexible pad applied to an area of the body targeted for treatment. These devices are termed a cryotherapy unit (CTU). CTUs that are currently in use allow for extended application of cold that can issue in tissue necrosis and/or neuropathy. We have developed a new technology that retains the therapeutic benefits of cryotherapy while obviating the pathway to NFCI and providing additional benefit for the wound healing process. The operational principle of this technology is to control the time modulation of blood flow, and therefore the state of local ischemia, to tissue. Laboratory proof of concept trials have been conducted on more than two hundred subjects. We hope to begin initial clinical trials with this technology this year. Three patent applications for this technology have been filed. Our first two scientific papers are in review, and two additional papers are nearly ready for submission. Both technologies are incorporated into enquiry-based learning materials disseminated for use in high school engineering classes and incorporated into a new textbook being authored by the PI.
