Surgery – Isolation treatment chambers – Incubators
Reexamination Certificate
2001-10-23
2004-07-13
Lacyk, John P. (Department: 3736)
Surgery
Isolation treatment chambers
Incubators
Reexamination Certificate
active
06761682
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to a support for patients and particularly to a patient thermal support device that provides an elevated and protected support surface for a patient and that protects and minimizes the disruption of the environment immediately surrounding the patient. More particularly, the present invention relates to a support device that controls the environment immediately surrounding the patient to minimize convective and evaporative heat loss from the patient so that the patient's own body warmth can keep the patient warm. The present invention can additionally be configured to warm a patient if desired using both convective and radiant warming techniques.
Incubators and radiant warmers have both been used to maintain the appropriate body temperature of small or premature infants. An incubator provides a generally transparent enclosure within which heated air is circulated to minimize the heat loss of the patient. In addition, heat is transferred to the patient via convective heat transfer. Incubators are typically provided with a large access door to allow for placement or removal of the infant in the incubator as well as supplemental access ways such as hand ports or small entry doors to permit routine care of the infant while minimizing heat loss from the incubator and the infant.
Radiant warmers provide for continuous and open access to an infant to accommodate a high frequency of intervention by the caregiver. Radiant warmers transfer heat to the patient via radiant heat transfer, typically from infrared heaters which emit infrared energy that is absorbed by the patient. The infrared heater is typically mounted to a support which is suspended above the patient support surface of the radiant warmer. Radiant warmers typically include no canopies or other enclosures that are commonly available on infant support devices to minimize the evaporative water losses of infants because such canopies or enclosures might obstruct the caregiver's access to the infant.
Patients can suffer from conditions that render it desirable to minimize contact between the patient's skin and objects, even including objects such as blankets. In addition, it is occasionally necessary for caregivers to have constant and ready access to the patient in certain critical care situations. What is needed is a patient support device that provides for continuous and open access to a patient while warming the patient should such warming be desired and that can be configured to minimize the evaporative water losses and resultant evaporative heat losses from the patient so that the patient can be uncovered while supported by the device.
According to the present invention, a patient support and environmental control apparatus is provided. The apparatus comprises a frame and an upwardly-facing patient-support surface carried by the frame. In addition, an air curtain generator is mounted to the frame. The air curtain generator provides first and second curtains of air. The patient-support surface has a perimeter and the first and second curtains of air originate adjacent to the perimeter and converge at a point positioned to lie above the patient-support surface. The first and second curtains of air cooperate with the patient-support surface to define a patient space.
A patient can experience heat loss through any of the mechanisms of conductive, convective, and radiant heat transfer, as well as evaporative heat loss that results from the evaporation of moisture from the patient's body. Conductive heat loss accounts for a very low portion of the heat loss of a patient and radiant heat loss can be minimized by heating surfaces such as platforms and walls surrounding the patient. Evaporative and convective heat losses can be controlled by controlling the air near the patient. Factors that operate to influence the extent of evaporative and convective heat losses include the velocity of the air near the patient, the moisture content of the air near the patient, and the temperature of the air near the patient.
The air curtains cooperate with the patient-support surface to define a patient space that is protected from disturbances from outside of the patient space. The air curtains define an effective barrier to atmospheric influences outside of the patient space so that the patient space is generally unaffected by changes in the environment surrounding the patient thermal support device. At the same time, the patient thermal support device can be operated so that there are no physical barriers between the patient and the caregiver, providing the caregiver with continuous and open access to the patient even when the air curtains are in place.
In preferred embodiments, the patient thermal support device in accordance with the present invention uses air curtains to blanket the patient and to create a “thermo-neutral” environment that insulates the patient from heat loss and allows the warmth generated by the patient to keep the patient warm. This device provides caregivers with unobstructed access to patients supported on the platform without the need to cover or in any other manner contact the patient.
A “dry” object can be warmed by blowing dry warmed air onto the object to effect a convective heat transfer. Likewise, a wet object can be warmed by blowing warmed air onto the object. The warming of the wet object can be maximized when the blowing air has a sufficient moisture content that there is no net loss of moisture by the object. However, a patient is more moist than any air that can be delivered to the patient by currently known techniques. As a result, as the velocity of the air engaging the patient increases, the evaporative moisture loss from the patient increases and the evaporative heat loss suffered by the patient increases.
In other words, when warmed air is delivered to the patient there are competing heating effects including a negative heating effect due to evaporative heat losses and a positive heating effect due to the convective heat transfer. For example, when air at 38 degrees C. that is not supplemented by moisture is delivered to the patient at a velocity below approximately 0.15 meters per second (0.49 feet per second), the heating due to convective heat transfer is greater than the heat loss due to evaporative moisture loss so that a net positive heat transfer to the patient occurs. However, when the air delivered to the patient is above approximately 0.15 meters per second (0.49 feet per second), the evaporative heat losses start to work against the convective gains so that at some higher threshold air velocity, the evaporative heat losses withdraw heat from the patient at a faster rate than convection supplies heat to the patient, so that increasing air velocity above the threshold velocity causes a net withdrawal of heat from the patient.
Although the primary purpose of the air curtains is to minimize the disturbance of the cloak of air surrounding the patient, the apparatus provides some convective heating by directing air from at least one additional air curtain toward the patient. The presently preferred embodiment of the patient thermal support device thus includes two opposing air curtains along the sides of the patient-support surface directed upwardly to form an air curtain “tent” above the patient resisting the ingress of air from outside of the patient space through the air curtains and into the patient space. Also, two additional air curtains originating at ends of the patient-support platform directed toward the patient are provided for convective heating of the patient.
In addition, for patients requiring less intervention, the patient thermal support device can be operated in an enclosed mode in which a canopy over the patient-support surface is lowered to engage side walls to enclose the patient space. Moisture can be added to the air curtains to minimize the moisture gradient between the patient and the cloak of air surrounding the patient. Although there is typically a large moisture gradient between
Donnelly Michael M.
Goldberg Charles
Gutwillig Alan
Moll Robert G.
Newkirk David C.
Barnes & Thornburg
Hill-Rom Services Inc.
Lacyk John P.
LandOfFree
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