Abstract:
An apparatus and corresponding method are provided for treating or preventing at least one of brain, brain-stem and associated nervous tissue injuries in a mammal suffering from decreased or compromised blood flow to the brain. The apparatus includes a helmet configured to rest unsupported on the head of a mammal. The helmet includes outer and inner shells with at least one cavity intermediate the outer and inner shells for holding a coolant fluid within the at least one cavity, and a coolant source in communication with the helmet, the coolant source instantaneously providing a coolant fluid chilled to a temperature sufficient to slow the metabolism of the brain. When the coolant source is activated, the helmet becomes instantly chilled rapidly cooling the brain to a temperature sufficient to slow the metabolism of the brain a sufficient amount so that the mammal remains neurologically intact while efforts are made to restore regular blood flow to the brain of the mammal.

Description:
This application is a continuation in part of U.S. patent application Ser. No. 08/910,156, filed on Aug. 13, 1997 now abandoned, which is a continuation in part of U.S. patent application Ser. No. 08/580,841 now abandoned, filed on Dec. 29, 1995, and of U.S. patent application Ser. No. 08/447,812 filed May 23, 1995, U.S. Pat. No. 5,913,885 which is a continuation of U.S. patent application Ser. No. 08/117,417 filed Sep. 7, 1993, now abandoned, which is a continuation of U.S. patent application Ser. No. 07/704,038 filed May 22, 1991, now U.S. Pat. No. 5,261,399. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The invention relates generally to treating ischemic and anoxic brain injuries. More particularly, the invention provides an apparatus and method for cooling of the brain and maintaining it at a temperature below normal body temperature during trauma or other periods of decreased or compromised blood flow due to, for example, stroke. With the invention, the brain and associated neurologic tissues survive the anoxic or ischemic trauma intact. The victim recovers with increased chances of survival and less chance of pennanent brain damage. 
     2. Description of Related Art 
     When an ischemic or anoxic injury occurs, the brain is deprived of freshly oxygenated blood. For example, this situation typically occurs during cardiac arrest, respiratory arrest, stroke and other cerebrovascular trauma, suffocation, drowning, strangulation, electrocution, toxic poisoning (carbon monoxide, cyanide, etc.), metabolic insults or other similar trauma. Without a steady supply of freshly oxygenated blood, the brain ceases to function and after resuscitation, most patients will suffer some damage to the brain and associated neurologic tissues. 
     For example, among cardiac arrest victims overall less than 10% survive neurologically intact and without significant brain damage. The other approximately 90% either die or sustain some neurologic injury from ischemia (i.e., lack of blood flow to the brain), or anoxia (i.e., lack of oxygen to the brain). Such frequency of neurologic injury occurs because after a cardiac arrest, basic cardiopulmonary resuscitation and advanced life support techniques, such as CPR, closed heart cardiac chest massage, and electroshock treatments, typically require fifteen to twenty minutes to regain circulation from a failed heart. Reversible neurologic damage begins as early as four minutes and irreversible neurologic damage begins as early as six minutes after circulation stops. To combat this potential neurologic injury, initial resuscitation efforts need to be directed toward reviving the brain in addition to resuscitating the heart. 
     As indicated above, anoxic and ischemic brain injuries from cardiac arrest, stroke or the like result in damage to the brain and associated neurologic tissues after about four minutes. In contrast, the heart can survive intact up to four hours after cardiac arrest, stroke or the like. The short viability of brain tissue upon deprivation of oxygenated blood is a result of the requirement of high amounts of nutrients for tissue maintenance. Brain tissue uses almost all of the nutrients supplied by the circulating blood for maintenance and stores only a small amount of nutrients. Absent blood flow to the brain, the small amount of stored nutrients is rapidly exhausted. Once exhausted, brain oxygen content is rapidly depleted. This oxygen depletion is traumatic and causes a series of reactions in the oxygen starved brain tissue cells. These reactions are believed to produce free radical ions, primarily consisting of the superoxide radical O 2 — − . These free radicals complex with proteins in the brain and associated neurologic tissues, altering respiration, energy transfer and other vital cellular functions, and irreversibly damage these tissues. 
     Efforts should be directed toward resuscitating the brain to attempt to extend the period of time the brain can function without oxygen while the patient remains neurologically intact. The medical literature is replete with examples of humans surviving extended periods of time (greater than 5 minutes) without oxygen being delivered to the brain. 
     Hypothermic therapy is one method of keeping the brain alive absent oxygen. It involves cooling the brain to a temperature where its metabolic activity is decreased. When the brain&#39;s metabolic activity is decreased, it uses much less oxygen and stored nutrients are exhausted slowly, while production of irreversibly damaging O 2 — −  free radicals is slowed and almost completely ceased. Thus, upon resuscitating the body from trauma, the patient emerges neurologically intact. For example, children revived after hours of submersion in very cold water have fully recovered with little if any neurologic damage. 
     Cooling for hypothermic therapy is presently achieved by cold room technology involving a heat exchanger in a heart-lung bypass. The surgery involved with the cold room technology takes place in a room the size of a meat locker or large commercial freezer. Cooling is also achieved by traditional devices such as natural or synthetic ice packs. Both of these devices and methods have several drawbacks. 
     A major drawback with the cold room technology is that it is invasive and quite expensive. It involves a team of highly trained, skilled medical personnel to operate and supervise a standard heart-lung bypass machine. This technology is not portable as it is restricted to a surgical operating room setting. Also, cooling is progressive, not instantaneous. Natural or synthetic ice packs, although portable and non-invasive, are disadvantageous because they are messy and do not rapidly achieve the low temperatures required to hypothermically shock the brain. Additionally, ice packs are ineffective in extremely hot environments such as deserts because they melt rapidly. 
     Previous inventions, such as those described in U.S. Patents Nos. 5,149,321 to Klatz et al. (&#39;321), U.S. Pat. No. 5,234,405 to Klatz et al. (&#39;405) and U.S. Pat. No. 5,261,399 to Klatz et al. (&#39;399), address the need to direct resuscitation efforts toward the brain, such that the victim can survive ischemic or anoxic trauma neurologically intact. Specifically, the &#39;321 and &#39;405 patents discuss devices and methods for resuscitating the brain such that its metabolism is slowed in order that the victim survive these metabolic insults neurologically intact. The &#39;399 patent discloses a device and method for externally cooling the brain and associated tissues. 
     Along with brain cooling, it can be advantageous to cool internal organs in the body such that their metabolism is slowed in order that they survive these metabolic insults fully intact. Typical current methods for cooling organs include ice packs or large scale machinery, such as that disclosed in U.S.S.R. Patent No. 1138152A (&#39;152). However, these methods and devices both have drawbacks. Ice packs are typically small in area, and when applied to a person, do not provide the rapid cooling necessary to slow the metabolism of internal organs. The device disclosed in the U.S.S.R. &#39;152 patent exhibits the drawback of providing cryogenic cooling that is too extreme for organ resuscitation during metabolic insults. This device is not suited for field use, as it is a large structure restricted to clinical facilities capable of handling dangerous fluids such as liquid nitrogen. Moreover, it must be used by a skilled surgical team and maintained by skilled technicians. 
     OBJECTS OF THE INVENTION 
     It is an object of this invention to non-invasively treat ischemic and anoxic brain injuries promptly upon cardiac arrest, stroke or the like whereby resuscitation efforts are applied in time for a patient to survive neurologically intact. By directing resuscitation efforts to treat the brain promptly, the invention allows medical personnel substantial additional time (beyond the critical four minute window) to regain the failed heart&#39;s circulation without the patient suffering permanent neurologic damage. 
     It is also an object of this invention to provide a method for treating anoxic or ischemic injuries to the brain whereby the patient survives neurologically intact. 
     It is also an object of the invention to provide a method of treating ischemic and anoxic brain injuries so as to inhibit free radical chemical species from complexing with proteins in the brain and neurologic tissue to avoid permanent irreversible damage. 
     It is also an object of the invention to non-invasively treat ischemic and anoxic brain injuries. 
     It is a further object of the invention to provide an apparatus which can substantially instantaneously cool the brain to a temperature where brain metabolism is slowed. 
     It is a further object of the invention to provide a portable apparatus for noninvasively treating anoxic and ischemic brain injuries which can substantially instantaneously cool the brain and associated neurologic tissue. 
     It is a further object of the invention to provide an apparatus for treating the aforementioned injuries by instantaneously cooling the brain, associated neurologic tissues and the upper spinal column. 
     It is a further an object of the invention to provide an apparatus for treating the aforementioned injuries, which is suited for field as well as clinical use and that can be operated by a single person with minimal medical training and experience. 
     It is a still further object to provide apparatus for cooling the brain which has very few parts, and is economical to manufacture and easy to use. 
     Other objects and advantages of the invention will be apparent to those skilled in the art from the following description and the appended claims. 
     SUMMARY OF THE INVENTION 
     The invention focuses on initial resuscitation efforts toward resuscitating the brain, due to its short viability, rather than the heart. The invention includes a noninvasive method which inhibits neurologic damage and resulting ischemic and anoxic injury on decreased or compromised blood flow, e.g., due to cardiac arrest, stroke or the like. The method includes placing and adjusting a scalp-enveloping helmet provided with means therein for circulation of a coolant fluid and circulating within said helmet a coolant fluid so as to lower the temperature of the patient&#39;s brain. In embodiments, substantially simultaneously with the circulation of coolant fluid through the scalp-enveloping helmet a neck supporting back plate shaped to correspond with the natural curvature of the neck is put in place to support the patient&#39;s neck in an upward position. The coolant fluid may also circulate through the back plate. 
     The invention also provides novel apparatus for alleviating ischemic and anoxic brain injuries in a mammal suffering from cardiac arrest, stroke or the like. The apparatus of the invention provides a helmet-like scalp-enveloping element provided with means therein for circulation of a coolant fluid. The scalp-enveloping element may be provided with inlet means for receiving a coolant fluid from a coolant fluid source to which it is operatively connected. The coolant source may include a portable coolant tank containing compressed liquid, the portable coolant tank being in fluid communication with at least one cavity of the scalp-enveloping element via a tube. Outlets may be provided in the scalp-enveloping element to permit the discharge therefrom of coolant fluid after circulation through the element. 
     Further, the coolant source may be a charging mechanism disposed on an outer surface of the outer shell of the scalp-enveloping element which upon activation produces the chilled coolant fluid. Alternatively, the coolant source may be disposed within the at least one cavity. For example, it may include a packet containing chemicals which are activated upon mixing to produce the chilled coolant fluid. Also, the coolant source may be a chemical disposed within the at least one cavity which produces the chilled coolant fluid when activated, e.g., by water. 
     Embodiments of the apparatus also include a neck supporting back plate shaped to correspond with the natural curvature of the patient&#39;s neck. The neck supporting back plate may also be provided with means therein to permit passage of coolant fluid therethrough. Means may be provided to allow for fluid communication between the scalp-enveloping element and the neck supporting back plate so that coolant fluid can be circulated through both pieces in series. 
     Inner and outer shells of the scalp-enveloping element may be formed of a soft, flexible material. Further, padding may be disposed on a surface of the inner shell of the scalp-enveloping element, the padding being of a material which allows the chill to quickly reach the brain. Additionally, the apparatus may be configured to be disposable and may include a flexible adjusting mechanism for maintaining the scalp-enveloping element on the head of a mammal. 
     Additionally, the scalp-enveloping element may include at least one coolant distributing system and may further include an inflatable bladder for pressing the scalp-enveloping element against the head of a mammal, whereby the head of the mammal is rapidly cooled. 
     Further, the scalp-enveloping element may include at least one temperature sensor for sensing a temperature of the chilled coolant fluid within the scalp-enveloping element. 
     Moreover, a layer of gel may be disposed on an inner surface of the inner shell and portions of the scalp-enveloping element may extend to cover the forehead and cheeks of the head of a mammal and a portion that extends to cover the eyes of a mammal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described with reference to the accompanying drawings, wherein like reference numerals identify corresponding or like components. 
     In the drawings: 
     FIG. 1 is a side view of a brain cooling apparatus according to the invention; 
     FIG. 2 is a cross-sectional view of a brain cooling apparatus according to the invention; 
     FIG. 3 is a cross-sectional view of the interface of the front and rear helmet pieces taken along line  3 — 3  of FIG. 1; 
     FIG. 4 is a cross-sectional view of the interface between the rear helmet and back plate pieces taken along line  4 — 4  of FIG. 1; 
     FIGS. 5A and 5B are side and top partial sectional views of the helmet adjustment mechanism; 
     FIG. 6 is a side view of another embodiment of a brain cooling according to the invention; 
     FIG. 7 is a cross-sectional view of the embodiment of the brain cooling apparatus shown in FIG. 6; 
     FIG. 8 is a cross-sectional view of the back plate of the embodiment of the brain cooling apparatus shown in FIG. 6; 
     FIG. 9 is a side view of a brain cooling apparatus of the invention where the coolant source is a charging mechanism; 
     FIG. 10 is a cross-sectional view of a brain cooling apparatus according to the invention where the coolant source is a chemical pack; 
     FIG. 11 is a perspective view of another embodiment of a brain cooling apparatus according to the invention; 
     FIG. 12 is a side cross-sectional view of the brain cooling apparatus of FIG. 11; 
     FIG. 12A is a side cross-sectional view of another embodiment of the brain cooling apparatus of FIG. 11; 
     FIG. 12B is a side cross-sectional view of another embodiment of the brain cooling device of FIG. 11; 
     FIG. 12C is a side cross-sectional view of another embodiment of the brain cooling apparatus of FIG. 11; 
     FIG. 13 is a side cross-sectional view of the chambers in the brain cooling apparatus of FIG. 11; 
     FIG. 14 is a top cross-sectional view of the chambers in the brain cooling apparatus of FIG. 11; and 
     FIG. 15 shows the brain cooling apparatus of FIG. 11 extended to provide total body cooling. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to FIG. 1, this embodiment of the brain cooling device  20  includes an adjustable multiple piece scalp-enveloping element or helmet  30 , a back plate  50  and a coolant source  62 . All of these components are designed to cooperatingly fit together. These components are lightweight and portable. They can be easily and quickly assembled together immediately prior to use at the site of the trauma. Detachment is also simple and quick. 
     The scalp-enveloping element or helmet  30  is of a universal size to insure conformity to all head sizes. While a two piece constriction is preferred, one-piece or multiple piece helmets are also possible. Each helmet piece  32 ,  34  has a hollow cavity  32   a ,  34   a  between the inner shell  36  and the outer shell  38  (FIG.  2 ). The helmet  30  includes flexible adjustment mechanisms  70  on both sides with cooperating coupling elements on each piece (or segment with one-piece helmets) enabling conformity to all head sizes. The front piece  32  of the helmet  30  has at least one outwardly extending nipple  40  to receive coolant, which enters this front piece  32  into the hollow cavity  32   a , whereby coolant circulates throughout all of the hollow cavities  32   a ,  34   a ,  52  (see FIG. 2) in each helmet piece  32 ,  34  and in the back plate  50 , cooling the inner shell  36  (FIG. 2) of the helmet  30 . The chill penetrates the inner shell  36  (FIG. 2) to contact the patient&#39;s head  42  at a temperature sufficiently low to quickly slow the brain&#39;s metabolism and inhibit potential neurologic damage. 
     The back plate  50  is preferably a one piece unit, although multiple piece construction is also permissible. Like the helmet pieces  32 ,  34 , the back plate  50  has a large hollow cavity  52  between the inner shell  56  and the outer shell  58  (FIG.  2 ). Back plate  50  supports the neck and permits additional cooling of the brain stem and upper spinal column. The back plate  50  can be maintained in fluid connection with the helmet  30  by body weight alone in an abutment relationship. However, fastening means such as buckles, straps, tape, snaps, rods, snap-together molding or other suitable fasteners can be used. Preferably, back plate  50  is saddle shaped at its upper portion  60  to accommodate and exaggerate the natural curvature of the neck, hyperextending it, while positioning it upwards. In this position, the carotid arteries or other large neck vessels are exposed and easily accessible for catherization involved with other resuscitation methods. 
     The coolant source  62  is preferably a compressed liquid such as carbon dioxide, which upon decompression becomes a cold gas. Prior to activation, these cold compressed liquids are preferably stored in portable containers such as tanks. Other suitable compressed liquids include freon or nitrogen. Alternatively, very cold liquids such as supercooled water, self freezing gel, packed liquid, ice water, or other such chemicals may be passed into the helmet through a tube  64  operatively connected to the nipple  40 . 
     An additional alternative coolant involves materials within the hollow cavities of the helmet, the back plate, or both, which chill upon activation when use is desired. For example, the helmet, back plate, or both could be prefilled with ammonium nitrate or equivalent thereof, which reacts endothermically when activated by water to chill these pieces. Alternatively, they could be provided with a charging mechanism  200  filled with compressed carbon dioxide or another compressed gas disposed on the outer surface of the helmet to provide instant cooling, as shown in FIG.  9 . FIG. 10 shows an example of a chemical packet  240  disposed within the inner cavity which activates when the membrane  270  between two separate chemical compartments  250 ,  260  is broken to mix the two chemicals, providing instant cooling. However, such a helmet would not be reusable unless configured so that the chemical packet  240  can be replaced. 
     FIG. 2 is a cross-sectional view of the helmet and back plate pieces of the first embodiment of the invention shown in FIG.  1 . This view shows the coolant&#39;s circulation between these components in detail. A specific circulation path is shown by arrows. 
     Coolant fluid, consisting of gas and/or very cold liquid, moves by expansion from the coolant source  62  through a tube  64  to the nipple  40  on the front piece  32  of the helmet  30 . This nipple  40  is preferably located on the front piece  32  of the helmet  30  since its angular orientation away from the body provides easy tube accessibility. However, single or multiple nipples can be placed on any of the helmet  32 ,  34  or back plate  50 . Coolant then enters the hollow cavity  32   a  in the front piece  32  of the helmet  30 , and circulates throughout the hollow cavities  34   a ,  52  of the rear helmet  34  and back plate  50  pieces. 
     Coolant may circulate throughout the helmet  32 ,  34  and back plate  50  through cooperatively aligned circulation ports  66   a ,  66   b ,  67   a ,  67   b  located on the respective ends of each helmet  32 ,  34  and back plate  50  piece. FIG. 3 shows these cooperatingly aligned circulation ports  66   a ,  66   b  at the interface of the front  32  and rear  34  helmet pieces respectively, while FIG. 4 shows these cooperatingly aligned circulation ports  67   a ,  67   b  at the interface of the rear helmet  34  and the back plate  50  pieces. The outer and inner shells between the hollow cavities in these helmet and back plate pieces is shown in phantom. While the illustrated port arrangement is preferred, any alternate arrangement is also permissible provided this arrangement permits chilled fluid to circulate throughout the helmet  30  and the back plate  50 . 
     Coolant exits the system through exhaust ports  68 , in the lower portion  69  of the back plate  50 . Additional exhaust ports may also be located on the helmet pieces to accommodate possible increased pressure. These exhaust ports would aid in eliminating any potential pressure build up in the hollow chambers which might damage the helmet  32 ,  34  or the back plate  50  pieces. 
     Preferred helmet  32 ,  34  and back plate  50  pieces may be made of a polymeric material such as blow molded plastics, nylon, fiberglass or rubber; metal or the like. This material is able to withstand contraction from rapid cooling and subsequent expansion upon warming without cracking. The inner helmet shell  36  is thin enough to conduct the chill from the hollow cavities  32   a ,  34   a ,  52  to the brain at a temperature sufficiently low to quickly slow brain metabolism, and inhibit potential neurologic damage. The inner helmet shell  36  is also thick and tough enough to support the patient&#39;s head  42  without deforming when the helmet is adjusted and placed on the patient&#39;s head  42 . However, soft shell or cloth-like helmets or helmet segments are also permissible provided they have a hollow cavity which can sufficiently receive and circulate coolant fluid. 
     Padding (not shown) may also be included on the inner helmet shell  36  and back plate inner shell  56  for additional comfort. However, this padding should be of a material such as sponge or the like which allows the chill to quickly reach the brain. 
     FIGS. 5A and 5B show adjustment and attachment mechanisms  70  for the helmet pieces  32 ,  34 . Exemplary elements include flexible tension straps  72  permanently mounted in a first anchor  74 , affixed to the outer helmet shell  38  and mounted in freely moving latch handles  76 . These flexible tension straps  72  are elastic enough to allow for adjustment to various head sizes, yet resilient enough to maintain the helmet&#39;s compression fit on the patient&#39;s head  42 . A first anchor  74  is permanently affixed to the outer shell  38  of the rear helmet piece  34  while the latch handle  76  is free and mounts at a point forward of a second anchor  78 . This second anchor  78  is permanently affixed to the outer shell  38  on the front piece  32  of the helmet  30 , and accommodates the flexible tension strap  72  through its center as the latch handle  76  abuts the second anchor  78  upon securement. While this arrangement between the latch handle  76  and anchors  74 ,  78  is preferred, the opposite arrangement of a permanently affixed anchor to the front helmet piece, including the permanently mounted flexible tension strap and a permanently affixed anchor to the rear helmet piece, is also permissible. Alternately, the helmet pieces can be held together by straps, buckles, tape, manual compression, or other similar attachment devices. 
     While this first embodiment is preferably a three piece unit (two helmet pieces and a back plate piece) the brain cooling device is also effective with only a front helmet piece which is activated with coolant and is manually pressed against the head. This is also true for the other helmet piece(s) and the back plate or pieces thereof, which can also function separately if equipped with nipples or other suitable means and provided with coolant sources. 
     This embodiment of the brain cooling device is relatively small. It is portable, can be fitted into a suitcase-like carrying case, and is suitable for field use, such as in ambulances, battlefields, athletic fields, aircraft, marine vehicles, spacecraft, emergency treatment facilities, and the like. It is lightweight and can be carried directly to the patient. In one example, the brain cooling device fits in a suitable carrying case and weighs approximately thirteen pounds or less. 
     FIG. 6 depicts a second embodiment of the brain cooling device  100 . This embodiment is made of two pieces: a one piece helmet  110  with front and rear segments  112 ,  114  in combination with a back plate  130 . Both the helmet  110  and the back plate  130  may be operatively connected to coolant sources (not shown). The coolant sources  112  employed with this embodiment are similar to those disclosed above in relation to the first embodiment. Like the first embodiment, these components are preferably lightweight and portable. They can be easily and quickly assembled together immediately prior to use at the site of the trauma. Detachment is simple and quick. Although these components are designed to operate as a unit, either the helmet  110  or the back plate  130  can be used separately should it be necessitated or desired. 
     The preferred helmet  110  is of a universal size to insure conformity to all head sizes. The helmet has inner  116  and outer  118  shells with a cavity  120  therebetween (FIG.  7 ). The two helmet segments  112 ,  114  are separated by a side-to-side baffled connector  122 . This baffled connector  122  is preferably of an elastomeric or other suitable flexible material with several folds on both shells. This baffled connector  122  allows the helmet  110  to be adjusted to various head sizes. While a side-to-side connection is preferred, a front to rear connection is also permissible. While baffled or folded connectors are preferred, other flexible, resilient, elastomeric connectors are also suitable. Also, while two helmet segments  112 ,  114  are preferred, additional segments are also permissible provided these segments are separated by baffled or other suitable connectors. Flexible adjustment mechanisms  124 , preferably on both sides of the helmet  110 , provide further adjustability. These adjustment mechanisms may be identical to those disclosed for the preferred embodiment as illustrated in FIG.  5 . 
     The front helmet segment  112  has at least one outwardly extending nipple  125  to receive coolant from a tube  126 . The nipple  125  in the front helmet segment  112  extends into the hollow cavity  120  for circulating coolant throughout the entire hollow cavity  120  (see FIG.  7 ), cooling the inner shell  116  of the helmet  110 . The chill penetrates the inner shell  116  to contact the patient&#39;s head  127  at a temperature sufficiently low to quickly slow the brain&#39;s metabolism and inhibit potential neurologic damage. The helmet  110  also includes exhaust ports  128  at its lower end to allow coolant to leave the helmet  110  and equalize pressure, whereby the helmet  110  does not crack or sustain other damage. 
     The back plate  130  provides additional cooling for the brain stem and upper spinal column. It is preferably a one piece unit, although multiple piece construction is permissible. Like the helmet  110 , the back plate  130  has a large hollow cavity  132  between the inner shell  134  and outer shell  136  (FIG.  8 ). The back plate  130  is separate from the helmet  110  during use. The back plate  130  includes a centrally positioned nipple  140  to receive coolant. Single or multiple nipples placed at other locations on this back plate or any pieces thereof are also permissible. The back plate  130  includes exhaust ports  142  along the perimeter  144  of the back plate&#39;s lower portion  146  to allow coolant to leave, equalizing pressure in the cavity  132  to prevent damage to the back plate  130 , such as cracking. Additional or substitute exhaust ports can be placed anywhere on the back plate. 
     Like the preferred embodiment, this back plate  130  supports the neck. It has a saddle shaped upper portion  148  to accommodate and exaggerate the natural curvature of the neck, hyperextending it, while positioning it upwards. In this position, the carotid arteries or other large neck vessels are exposed and easily accessible for catherization involved with other resuscitation methods. 
     FIG. 7 is a cross-sectional view of a helmet of this second embodiment. This view shows the coolant&#39;s circulation between the helmet segments  112 ,  114  in detail. The specific circulation path is shown by arrows. 
     Coolant fluid, comprised of gas at a low temperature or very cold liquid, moves by expansion from the coolant source (not shown) through a tube  126  operatively connected to the nipple  125  on the front segment  112  of the helmet  110 . This nipple  125  is preferably located on the front segment  112  of the helmet  110  since its angular orientation away from the body provides easy tube accessibility. However, single or multiple nipples can be placed on any of the helmet segments  112 ,  114 . Coolant then enters the hollow cavity  120  in front helmet segment  112 , and circulates through the baffled connector  122  to the rear helmet segment  114 . Coolant exits the system through exhaust ports  128 , preferably located on the lower portion of the rear helmet segment  114 . Additional or substitute exhaust ports may also be located anywhere on any of the helmet segments to accommodate possible increased pressure. 
     FIG. 8 is a cross-sectional view of a back plate  130  of this second embodiment. This view shows the coolant&#39;s circulation within this back plate&#39;s hollow cavity  132  between the inner and outer shells  116 ,  118  in detail. The circulation path is shown by arrows. 
     Similar to the helmet  110 , the coolant fluid, comprised of very cold gas or liquid, moves by expansion from the coolant source (not shown) through a tube  149  to the nipple  140  on the bottom side  152  of the back plate  130 . This nipple  140  is preferably centrally located on the curved upper portion  148  to provide easy tube accessibility. Coolant then enters the hollow cavity  132  and circulates throughout the entire back plate  130 . Coolant exits the back plate  130  through the exhaust ports  142 , preferably located on the perimeter  144  of the lower portion  146 . Additional or substitute exhaust ports may also be located anywhere on this back plate  130  to accommodate possible increased pressure. 
     Similar to the first preferred embodiment, the helmet  110  and back plate  130  of the embodiment may be made of a polymeric material such as blow molded plastics, nylon, fiberglass, or rubber; metal; or the like. This material is able to withstand contraction from rapid cooling and subsequent expansion upon warming without cracking. The inner helmet shell  116  is thin enough to conduct the chill from the hollow cavity  120  to the brain at a temperature sufficiently low to quickly slow brain metabolism and inhibit potential neurologic damage. The inner helmet shell  116  is also thick and tough enough to support the head without deforming when the helmet  110  is adjusted and placed on the patient&#39;s head  127 . However, soft shell or cloth-like helmets are also permissible provided they have a hollow cavity which can sufficiently receive and circulate coolant fluid. 
     Padding (not shown) may also be included on the helmet  116  and back plate  134  inner shells for additional comfort. However, this padding should be of a material such as sponge or the like which allows the chill to quickly reach the brain. 
     While these two preferred embodiments described in detail herein are portable devices particularly suited for field use, they are also suited for stationary, clinical use. Should a clinical device be desired, these two portable embodiments could be made larger and modified accordingly for such use. 
     In operation, the brain cooling apparatus of the invention sufficiently chills the brain to slow its metabolism, allowing for continued resuscitation efforts. As previously stated, the invention comprises a method of treating anoxic and ischemic injuries suffered as a result of cardiac arrest, respiratory arrest, stroke or other cerebrovascular trauma, suffocation, drowning, electrocution, toxic poisoning (carbon monoxide, cyanide, etc.) metabolic insults or other similar trauma. 
     Specifically, operation of the apparatus involves merely placing the patient on the back plate (if a back plate is present), attaching the helmet pieces (if using a multiple piece helmet), adjusting the helmet on the patient&#39;s head, attaching the helmet to the back plate, attaching a tube from the nipple(s) to the coolant source(s) and activating the coolant source(s). This process is quite simple and can be performed at the trauma site by a person with minimal, if any, medical training. 
     FIG. 11 shows another embodiment of the brain cooling apparatus according to the invention. The brain cooling apparatus  330  includes an outer shell  338  connected to an inner shell  336  that when attached form a cavity  325  therebetween (see FIG.  12 ). The apparatus  330  is designed to move coolant fluid (liquid or gas) from a coolant source  362  and circulate it through cavity  325  to cool the head  342 . Inflow and outflow lines  364 ,  364  for delivering and returning coolant fluid from and to the coolant source  362  are attached to outer shell  338 . 
     Alternatively, a chemical pack  260 A, such as that shown in FIG. 10, can be disposed within cavity  325 , as shown in FIG. 12C, which activates when the membrane  270 A between two separate chemical compartments  250 A,  260 A is broken to mix the two chemicals, providing instant cooling. In such a case, the helmet can be configured to be reusable so that the chemical packet  240 A can be replaced. 
     An inflatable bladder  382  is positioned along the exterior face of the outer shell  338 . The bladder  382  upon inflation and subsequent filling with gas (e.g. air) from a gas source  380 , the gas supplied through lines  381 ,  381 , press the inner and outer shells  336 ,  338  (now cooled) against the head  342 . This contact permits a greater heat transfer between the brain cooling apparatus and the head  342  and therefore more rapid body cooling. 
     The inner and outer shells  336  and  338  are joined with outer bladder layer  384  at their peripheral edges (not shown) to form an airtight seal by any one of several conventional bonding constructions such as ultrasonic welding, vibration welding, radio frequency welding, heat welding, electromagnetic welding, and induction welding, as well as thermal sealing and adhesive bonding techniques. The preferred method of joining the inner and outer shells  336 ,  338  and the outer bladder layer  384  is heat sealing. 
     Coolant channels  386 , shown in detail in FIGS. 13 and 14, are formed between inner and outer shells  336 ,  338  and are preferably pentagonal in shape, although other shapes (e.g. hexagonal, triangular, circular, elliptical) are also permissible. The channels  386  include opening  387  in their walls  388 , and protrusions  389  at their center. These structures provide turbulent flow for the coolant for effectively cooling. Alternatively, the coolant channels  386  may include the protrusions alone absent the walls. 
     Alternatively, as shown in FIGS. 12A and 12B, the spaces between the inner and outer shells  336 ,  338 , and/or between the outer shell  338  and the outer bladder layer  384  can define lumens  385  for coolant circulation systems, or gas circulation systems, respectively. The coolant circulation systems, or gas circulation systems would include linear joints (not shown), preferably of a length in the range of approximately 0.2 cm to 10.0 cm, formed by heat sealing portions between the inner and outer shells  336 ,  338 , and/or between the outer shell  338  and the outer bladder layer  384 . These linear joints, which may be uniform in size and may be formed in various patterns, such as in a series of side-by-side, parallel rows, or staggered in diagonal or lightening bolts patterns, create a pathway for coolant fluid, or gas to circulate. Such an arrangement permits high fluid flow rates while preventing ballooning, which reduces skin contact, of the apparatus layers. 
     Tubes (not shown) also may be employed, in a serpentine or similar pattern to maximize cooled surface area, located between the inner and outer shells  336 ,  338 . The tubes may have cross-sectional shapes that are circular, rectangular, square, oval, triangular, diamond, or any other shape suitable to accommodate coolant flow through the tube. The tube or tubes may be attached to either the inner shell  336 , the outer shell  338 , both or not attached to either. 
     A preferred coolant source  364  is a refrigeration unit capable of generating cooled fluid (liquid and/or gas) at temperatures as low as −60 degrees Fahrenheit and at pressures as great as 60 psig, and preferably at temperatures approximately—10 degrees Fahrenheit or below and pressures approximately 10 psig or above. Multiple coolant sources are also permissible. Coolant fluid may be any fluid, liquid or gaseous, including chilled water and slushed ice, capable of imparting the desired cooling effect. 
     Additives may be included to lower the freezing point of the coolant fluid, such as propylene glycol. Propylene glycol exhibits low corrosiveness and low volatility. A bacteriostatic agent may also be added to prevent the growth of bacteria and other organisms. 
     Additional coolant fluids include R-134A (Forane, 1,1,1,2-tetrafluoroethane), which is considered to be one of the most environmentally safe refrigerants available. R-134A is nonflammable, does not contain known reproductive toxins, is insoluble in water, has a freezing point below (−)101° C., and is generally stable at low temperatures. Furthermore, R-134A is non-irritating upon contact with the skin, other than by potential excessive cooling. R-134A does not contain components listed by NTP, IARC, or OSHA as being carcinogens. R-134A has a low acute inhalation toxicity (4 hour CCSO in the rat &gt;500,000 ppm). 
     The coolant inflow and outflow lines  364 ,  364  supply coolant fluid from and return the coolant fluid to the coolant source as part of a coolant circuit. These coolant inflow and outflow lines  364 ,  364  are preferably directly connected to the coolant source and the outer shell  338 , as shown in FIG. 11, via airtight ports (not shown). Alternatively, the coolant outflow line need not be connected back to the coolant source if a coolant circuit is not desired. Multiple coolant inflow and outflow lines (not shown) are also permissible with this apparatus. The multiple inflow and outflow lines may be directly connected to the coolant source or may be branched and connected to main coolant inflow and outflow lines. Further, the coolant inflow and outflow lines  364 ,  364 , supplying the brain cooling apparatus  330  could include valves anywhere along their length. These valves may be controlled manually, pneumatically, hydraulically, magnetically, or electronically. Thermistor temperature sensors and microprocessors may be used to control the brain cooling apparatus and allow zone cooling, or to enhance coolant control. 
     As previously described, the outer bladder layer  384  defines the inflatable bladder  382  or alternatively multiple bladders (if partitioned accordingly) that is designed to be inflated with liquid, or gases, to press the inner and outer shells  336 ,  338  into contact with the head  342 . Alternatively, the bladder(s) may be attached to the outer shell  338 . The bladder(s) may be inflated with gas from a source  380 , the source  380  including pressurized air tanks, portable or solid state air compressors, manually or automatically driven air pumps, or vapor generating chemical reactions. The gas used to inflate the bladder(s) may include any suitable non-toxic gas, including air, nitrogen, helium, oxygen, and carbon dioxide. 
     Alternatively, the gas source may include several valves for attaching to multiple gas lines. Each valve may be under microprocessor control or each valve may be part of a series of automatically cycling valves. This allows each valve to control the supply of inflation gas to a single bladder (in multiple bladder devices) to create wave-like inflation of the bladders. 
     Another alternative gas supply may provide gas in repeating inflation and deflation modes, in response to preset or regulated pressures, or time, or flow. The gas source would include a supply of any of the inflation gases disclosed above, and would also include specialized pumps, pressure sensors and valves, electronically connected, and preferably under microprocessor control (with a manual override) that serve to inflate the bladder(s) and then deflate them when a preset pressure is reached. Once deflation reaches a preset pressure, the bladder(s) is/are inflated. This can continue for as long as desired, as is controlled by the user. 
     The bladder  382  is connected and supplied inflation gas thereto, from the gas source  380  by lines  381 ,  381  or multiple lines (not shown) from the gas source  380 . Multiple gas sources are also permissible. The lines  381 ,  381  may be permanently attached but are preferably removably connected. The lines  381 ,  381  connect to the outer bladder layer  384  via airtight ports (not shown). The ports preferably include valves (not shown), such as a check valve or stop cock to prevent escape of gas from the bladder  382 , once the lines  381 ,  381  are disconnected, or to permit the input or discharge of gas as desired. The ports may be located anywhere along the outer bladder layer  382 . 
     The inner and outer shells  336 ,  338  and the outer bladder layer  384  are preferably made of a material impervious to liquid and gas. Thermoplastic elastomers (TPEs) which can be made into film or sheeting by extrusion casting, calendering, or other manufacturing processes are appropriate. Included among these TPEs are polyurethane, copolyesters, styrene copolymers, olefins, and elastomeric alloys. Preferred TPEs will have good elongation and tear strength, good resistance to flex fatigue at both low and high temperatures, good dynamic properties, resist water, alcohols, and dilute bases and acids, and exhibit good thermal conduction properties to permit the rapid transfer of heat from the person or cadaver. The materials for the inner and outer shells may also comprise TEFLON® TYVEK® or Gore-tex® type materials or the like. 
     The material of the inner shell may include microscopic pores. These microscopic pores permit small quantities of coolant to enter the cavity (on the side of the inner layer contacting the body) and moisten the skin. This skin moistening destroys the insulative air layer that exists on the skin and allows direct contact with the cooled inner layer for maximum heat transfer to the head. 
     The inner shell may also be coated with gel, with gels such as any commercially available EKG electrode gel or ultrasound gel. The gel could be retained under paper, wax-based or TYVEK® type sheets, that peel off when use of the apparatus is desired. 
     The material for the outer bladder layer may also comprise TEFLON®, TYVEC® Gore-tex®, nylon, rubber or any non-porous flexible material. 
     Alternatively, the outer bladder layer may be eliminated and the inner and outer shells may be pressed against the head by a formfitting stretchable cap that fits snugly on the head. Also, the inner and outer shells may extend down around the eyes to provide cooling to the eyes. Further, the gas source may be replaced by a vacuum source for creating a vacuum in the cavity formed between the head of a patient and the inner shell. Also, the brain cooling device can extend down the back, e.g., to provide total body cooling, preferably in sections, as shown, by example, in FIG.  15 . 
     Similar to the other embodiments, operation of the apparatus involves merely placing and securing the brain cooling apparatus on the patient&#39;s head; attaching the coolant inflow and outflow lines to the outer shell and the coolant source(s); attaching the gas inflow and outflow lines to the outer bladder layer and the gas source(s); and activating the coolant source(s) and the gas source(s). This process is quite simple and can be performed at the trauma site by a person with minimal, if any, medical training. 
     These embodiments of the apparatus are portable and suitable for field use, such as in ambulances, battlefields, athletic fields, aircraft, marine vehicles, spacecraft, emergency treatment facilities, and the like. They are lightweight and can be carried directly to the patient. These embodiments can also be modified for clinical (hospital type) settings. While the apparatus of the present invention is preferably designed for the treatment of humans, it can also be used in treating other mammals such as dogs, horses or the like, and sized accordingly. 
     While particular embodiments of the invention have been shown, it will be understood, of course, that the invention is not limited thereto, since modifications may be made by those skilled in the art, particularly in light of the foregoing teachings. It is therefore, contemplated by the appended claims to cover any such modifications as incorporate those features which constitute the essential features within the true spirit and scope of the invention.