Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
1999-06-18
2001-06-12
Cohen, Lee (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C607S108000, C607S109000
Reexamination Certificate
active
06245094
ABSTRACT:
BACKGROUND OF THE INVENTION
Adjusting and maintaining a person's body temperature using external means has proven to be a difficult task in many instances. One means of adjusting and maintaining body temperatures is to submerge the patient into a bath of water. The water temperature in the bath is chosen to properly adjust the patient's temperature. Although this technique has proven to be quite useful in many applications it is not particularly appropriate in many instances.
For example, this approach often does not fare well with hypothermia patients. In such cases, the patient is typically submerged in a very warm bath to raise the body temperature of the patient. The use of a water bath is, however, frequently impractical, for it requires the use of a bath tub of sufficient size to completely submerge a patient, and it also requires close regulation of water temperature. Furthermore, this approach is time consuming because time must be spent preparing the warm bath. In cases such as at sea when a person has fallen overboard, these impracticalities can prove to be quite costly.
Another situation where the use of a water bath is impractical for regulating body temperature is in a clinical environment, including a surgical environment. Operating rooms are most often maintained at fairly cold temperatures to aid in the comfort of the surgical personnel. Unfortunately, it is not typically desirable for the patient to be exposed to such cool temperatures. In colder temperatures, patients tend to bleed more profusely and many patients may become uncomfortably chilled by the cold.
Patient warming approaches which have been used in clinical environments, but which are not usually practical in surgery, include warm air blanket systems and water blankets. Blankets filled with warm water suffer poor overall heat transfer in view of a failure to contact low points in the body contours. Further, due to compression of the water blanket against heated areas, blood flow from those heated areas may be limited and local tissue damage may result. With warm air systems, warm air flows through holes from an inflated blanket toward the patient. With the air flowing directly against the patient, uniform heat distribution to the patient's skin is assured. However, the warm air presents a relatively low heat transfer coefficient.
With the poor heat transfer of the air and water blankets and with the requirement that temperature be held sufficiently low to prevent tissue damage, it is necessary that the blankets cover large surface areas. As a result, they become cumbersome and expensive. Further, by warming such a large surface area of the skin, vasodilation in that large area can result in a significant and undesirable redistribution of the blood flow in the body.
SUMMARY OF THE INVENTION
The present invention presents a system for safely and quickly regulating a patient's body temperature. A heating member heats a portion of the patient's body. By assuring a high heat transfer coefficient, only a small area of the patient need be heated. Less than 5% of a patient's total surface area, and even just the patient's forehead, need be heated.
In a preferred embodiment, a portion of the patient's body is appropriately enclosed. Heated vapor is mixed with air to produce a saturated mixture. This mixture is delivered into the isolated environment created by the enclosure. The vapor surrounds the portion of the patient's body that lies within the enclosure. Since the patient's body is cooler than the heated vapor, the vapor condenses causing heat carried by the vapor to be transferred to the patient's body. The net result is that the patient's body temperature is quickly, efficiently and safely regulated.
The system preferably also includes a temperature monitor for monitoring the patient's body temperature as the vapor and air mixture are being generated. An ear monitor which senses thermal radiation from the ear is ideal for the temperature monitor. The ear temperature monitor may monitor tympanic temperature or the temperature of the ear canal at the outer ear. The latter is preferably ambient temperature compensated to approximate tympanic temperature. The monitored temperatures are preferably fed back to a control means that regulates the operation of the vapor generator. As soon as a desired body temperature is achieved, the vapor generation may be significantly reduced or halted. Moreover, if a given body temperature must be maintained, a constant monitoring capability is provided.
The vapor produced by the vapor generator is preferably a saturated mixture of water vapor and air. Water vapor is an ideal candidate because of the magnitude of heat transfer that occurs when it condenses and secondly, because of its great availability. The vapor and air mixture should be heated to a dew point temperature no greater than about 43° C. (110° F.) and certainly no higher than 47° C. to avoid tissue damage. At 43° C., the water vapor achieves a significant level of heat transfer without causing any harmful tissue damage. The critical parameter for minimizing tissue damage is the difference in temperature between the vapor and the patient. Since a small temperature difference is maintained by the present invention, tissue damage is unlikely. The high heat transfer coefficient obtained by using condensing vapor plays a critical role in maintaining this small temperature differential. To obtain that condensation, the dew point temperature of the vapor must be greater than the blood temperature and, more specifically, greater than tympanic temperature. Normal body temperature is about 37° C., but for lower skin temperatures dew point temperature of 30° C. may be appropriate. Overall, the preferred temperature range is 40° C. to 43° C.
There are two approaches of the invention that are of particular interest. In the first approach, the portion of the patient below the head is enclosed within the enclosure. To provide such an enclosure a body bag device may be utilized. The device is preferably non-porous so that the vapor is kept entirely within the enclosure. In addition to the features previously described, this embodiment also includes a recycling means for collecting condensation and air from within the enclosure. Since the condensation and returning air are already heated, they require less heating when recycled than was initially required. This particular embodiment is ideal for a quick and easy treatment of hypothermia patients.
The other and most preferred approach is well suited for surgical applications as well as hypothermia patients. Instead of enclosing the entire body as in the previous embodiment, this additional embodiment encloses only a small portion of the body such as the patient's forehead. The water vapor surrounds an area of the patient's head and heats blood flowing through the patient's head. The heated blood then travels throughout the patient's body warming the rest of the patient's body. As a result, the entire body temperature of a patient may be regulated merely by heating the patient's head.
Because this embodiment is designed for use in a surgical environment it is best that condensation and air not be recirculated. The condensation and air become contaminated when exposed to the patient and, therefore, should not be recycled in a sanitary surgical environment. An absorbent serves as a condensation gathering means to remove excess condensation. In addition, vents are provided to allow excess vapor to escape.
In the preferred embodiment, the enclosure is a manifold having a perforated surface contoured to follow the shape of a forehead and spaced from the forehead. Vapor is vented from beneath the manifold, and condensation is collected by absorbent material to either side of the manifold.
All of these embodiments offer quick and efficient means of regulating a patient's body temperature. The hardware necessary for such embodiments is limited and cost effective. Furthermore, these em
Cohen Lee
Exergen Corporation
Hamilton Brook Smith & Reynolds P.C.
Ram Jocelyn
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