Patient Support System

Abstract

In a bed for supporting and treating a hospital patient, a lamination of low and medium density plastic foam is enclosed in a pressurized container. An open pore foam layer on top of the container produces a flow of air from the top of the foam layer for patient ventilation. Control of the volume of air varies the degree of ventilation. The container is divided into airtight zones which can be independently pressurized to control the relative firmness of the support in different zones. The pressurizing air for the container is controlled to vary the relative firmness of support.

Description

BACKGROUND OF THE INVENTION

This invention relates to a hospital bed and more particularly to a plastic foam bed having a flow of ventilating air from the top thereof.

The comfort of a hospital patient is greatly enhanced by a bed which provides uniform support for the patient's body. Uniform support also helps prevent decubitus ulcers. Decubitus ulcers result from a loss of blood circulation caused by pressure on the skin, particularly pressure over a bony protuberance. If the pressure on areas of support exceeds the mean capillary blood pressure, these areas are vulnerable to decubitus ulcers. Other factors which contribute to decubitus ulcers are lack of proper ventilation, skin sheer, moisture and diet, but pressure is the most important and primary cause. These and other considerations are discussed in "Etiology of Decubitus Ulcers: An Experimental Study," Archives of Physical Medicine and Rehabilitation, Nov., 1961.

Attempts to equalize pressure on the patient's body have included the provision of liquid-filled mattresses, such as that shown in U.S. Pat. No. 3,108,293. Liquid-filled mattresses must have a cover to keep the patient out of contact with the liquid. This cover acts as a hammock and itself distributes pressure unevenly over the patient's body. Both conventional and liquid-filled mattresses prevent air from circulating freely over areas of the patient's body resting on the mattress.

A great advance in patient supporting beds was a fluidized granular bed shown in Hargest et al. U.S. Pat. No. 3,428,973. This bed includes a mass of granular material which is fluidized by air blowing upwardly through the mass. A patient resting on a pliable sheet on top of the mass of granular material is supported uniformly over all parts of his body. The use of beds of this type has been particularly successful in the treatment of burn victims, the prevention of decubitus ulcers and, in general, obviating the adverse effects of confinement to a hospital bed on patient recovery. The beneficial use of such beds is described in "Patients Float in Bed of Beads," Hospital Practice, May, 1969, Vol. 4, No. 5, page 91, and in "Bead Bed Floats Away Sores," Medical World News, May 16, 1969.

Unfortunately, it is not practical to provide fluidized granular type beds for all hospital patients because of expense and weight considerations.

Soft plastic foam has some characteristics of uniform support which make it attractive for possible use in a hospital bed. The use of plastic foam instead of fluidized granules would also be attractive from the cost standpoint. Employing low-density foam to support a patient provides a low-pressure uniform support by allowing the patient to sink down into the foam. Since the foam is a good insulator, heat and perspiration on the supporting areas becomes a problem. Attempts have been made to ventilate a foam mattress. For example, in the Figman U.S. Pat. No. 3,266,064, regularly spaced openings in the foam convey ventilating air to the patient.

SUMMARY OF THE INVENTION

In accordance with an important aspect of the present invention, the patient support includes a pressurized plastic foam filled container covered by an open pore foam sheet which serves as a plenum for the distribution of ventilating air to the supporting areas of the patient's skin.

In accordance with another aspect of the invention, the pressurized container encloses a lamination of layers of plastic foam of differing density.

In accordance with another aspect of the present invention, the pressurization of the container is controlled to vary the relative firmness of the support.

In this system, the softest support is that provided by the layers of low-density foam with no air pressure. As air pressure is increased, less and less of the patient's weight is supported by the foam. When maximum pressure is obtained, nearly all of the patient's weight is carried by the pressurized container.

In accordance with still another aspect of the invention, the pressurized container is divided into airtight zones which are independently pressurized to control the relative firmness provided different parts of a patient.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross section of the polyfoam and pneumatic support system of the invention;

FIG. 2 is a cross section of the pressurized container enclosing the lamination of soft and medium density foam layers;

FIG. 3 shows details of the pressurized container; and

FIG. 4 shows the support system in place in a conventional hospital bed.

DESCRIPTION OF A PARTICULAR EMBODIMENT

Referring to FIG. 1, the pressurized container 1 encloses a lamination of low and medium density plastic foams. The container is covered with an open pore foam layer 2 which acts as a plenum for a supply of ventilating air. This air is supplied from an air compressor 3 through the connecting hose 4. The use of an open pore foam as an air plenum has significant advantages in a support system of this type. For example, the distribution of air from the open pore foam is more uniform than the distribution from a box perforated on its top surface and placed beneath a foam mattress, as described in Science and Medicine, April-May, 1969, page 19. It is also more uniform than the flow of air through foam with openings extending all the way through the foam such as is shown in the aforementioned Figman U.S. Pat. No. 3,266,064.

Typically, the foam layer 2 may be a 2-inch thick open pore foam which is rigid enough that patient loading does not pinch off air flow through the pores, but soft enough to conform to the shape of the patient's body. One particular foam suitable for use in an open pore (reticulated) polyurethane foam available from Scott Industrial Foam Division of the Scott Paper Company, Chester, Pennsylvania, having 60- 30 p.p.i. (pores per inch). A uniform air flow of between 0.5 to 1.5 feet per minute can be obtained from the top surface of the foam layer 2.

In some applications, it will be desirable to include a top foam sheet 5 above the open pore foam 2. The top foam sheet 5 should be a low-density, semiclosed cell (not reticulated) foam. One foam suitable for use is the polyether urethane flexible foam available from Napco Chemical Company, Plainfield, New Jersey, having a nominal density of 1.10-1.35 pounds per cubic foot.

The pressurized container 1, open pore foam layer 2, and top foam sheet 5 are all enclosed in a fabric cover 6. The top of this cover particularly must be made of a material which will stretch, but which does not support the patient by a hammocking effect. The typical material suitable for use is a nylon stretch-type material sold under the trade name of Banlon.

The ventilating air supplied to the hose 4, and the pressurizing air supplied through the hose 4a, are supplied from the air compressor 3. The air compressor unit includes a flow control knob 7 and an airflow indicator 8. The ventilating air may be heated and humidified as required. The air compressor also includes a pressure control 9 and an air pressure indicator 10. The unit should be capable of pressurizing the container 1 up to a pressure of 2 p.s.i. The ability to change the firmness of support supplied by the pressurized container is quite desirable. It allows selecting the firmness particularly suited to the needs and desires of the individual patient. It is also desirable for an individual patient to vary the relative firmness of support from time to time to relieve monotony. One compressor suitable for use is the vane-type air compressor.

Referring to FIG. 2, the pressurized container 1 encloses a lamination of foams, the layers 11-14 being shown. The laminations are of increasing density. That is, in most applications it will be desired to have more dense foam at the bottom. Typically, the layer 11 may be a low-density semiclosed cell polyether urethane foam having an indentation load deflection (ILD) of 25 percent at 9 pounds. Layer 12 typically may have an ILD of 25 percent at 12 pounds; layer 13 an ILD of 25 percent at 15 to 20 pounds and layer 14 an ILD of 25 percent at 30 to 40 pounds.

The foam layers are enclosed in the fabric container 1 having an excess of fabric at the top to allow deflection uninfluenced by a hammocking effect. An air fitting 15 supplies the pressurizing air to the container. The container is divided into 4-inch square cells by tensile cords which are fastened to the top of fabric container 1 and to a board 16 in the bottom of the container. Of course, the cells may be larger or smaller than 4 square inches.

The attachment of the tensile cords between the board 16 and the top fabric is shown in FIG. 3. Note that the foam is compressed at the tie down at the corner of each convex pocket. Typical cords 17-20 divide the foam into 4-inch square cells. There is a dome of top fabric between each group of four cords. This allows depression of a particular cell without affecting other cells. The rows of cells along the edges may be pressurized separately from the other cells to allow a firm support along the edges of the bed. This provides firm support so that the edges of the container do not bulge out. This also provides a firm support at the edge when a person is getting into or out of the bed. As shown in FIG. 3, a separate piece of fabric 21 is used along the edge and is folded under to be attached to the baseboard along the line 22. This piece of fabric separates the enclosed cells from the remainder of the cells. This technique is also used to divide the rest of the sealed container into zones which can be separately pressurized.

As shown in FIG. 4, the container is divided into three separate control zones. Ducts 23, 24, and 25 supply separate sources of pressurizing air to the three zones. Zone control of firmness is desirable, for example, to allow the patient to sit on a relatively firm support while his back remains on a soft support. Also, zone control of firmness facilitates handling of a patient in a supine position on a bedpan. The capability of softening a zone under the buttocks while maintaining the remainder of the support firm allows sliding the bedpan under the patient instead of lifting the patient.

FIG. 4 shows the support system in place on a conventional hospital bed. The board 16 (not shown in FIG. 4) is hinged at appropriate places to allow bending along lines at the points 26, 27 and 28 so that the normal raising and lowering functions of a hospital bed can be accommodated. Auxiliary orthopedic support members, such as the contoured heel pad 29, can be inserted in the foam at the appropriate places.

The advantages of the patient support system of the present invention over a conventional hospital bed can be appreciated by the results of a simple pressure test. This test was conducted by inserting a pressure measuring sensor into different places on a conventional mattress and on a polyfoam support system of the present invention. The sensor included an air cell with opposed electrical contacts which closed when the pressure in the air cell was reduced to a measured level. This test is summarized by the following comparison of supporting pressures for a conventional mattress and a polyfoam support.

Position Conventional mattress Polyfoam __________________________________________________________________________ Lying Down under heel 165 mm. Hg. 65 mm. Hg. buttocks 39 14 4 inches above waist 5.8 7.5 Sitting Up With Upper Torso at 50.degree. Angle With Horizontal buttocks 33.6 24.6 midthigh 6.5 3 4 inches above waist 1.5 2 Sitting on Edge of Bed buttocks 72 39 midthigh 32 22.4 __________________________________________________________________________

The above comparison demonstrates the advantages of the polyfoam support in more nearly equalizing the distribution of pressure on the supporting areas of the patient. Note, for example, that midcapillary pressure on an average probably runs between 20 and 30 mm. of Hg. Note, also, for example, that the pressure measurements at 4 inches above waist are greater for the polyfoam support than for a conventional mattress. This indicates that the polyfoam support extends up into the small of the back to provide support in that area and to lessen the pressure on the other areas.

While a particular embodiment of the invention has been shown and described, it will be understood that various modifications may be made without departing from the true spirit and scope of the invention. The appended claims are, therefore, intended to cover any such modifications.

Claims

What is claimed is:

1. A system for uniformly supporting a patient comprising:

a lamination of layers of low- and medium-density plastic foam,

an airtight container enclosing said lamination,

means for pressurizing said container so that said layers of foam are pressurized to the desired degree of firmness,

tensile cords between the top and bottom of said container dividing said lamination of foam into pressurized cells,

an open pore reticulated uniform foam layer on top of said pressurized container,

an outer covering enclosing said pressurized container and said reticulated foam layer, and

a source of ventilating air connected to said open pore reticulated foam layer producing a flow of air from the top of said foam layer for patient ventilation.

2. The system of claim 1, and an air compressor supplying pressurized air to said container and supplying ventilating air to said open pore foam layer.

3. The system recited in claim 1 wherein said lamination has layers of foam of increasing density from the top to the bottom of said container.

4. The combination recited in claim 2 wherein said air compressor has controls for varying the pressurization of said container so that different degrees of relative firmness of said mattress can be obtained.

5. A system for uniformly supporting a patient comprising:

a lamination of layers of low- and medium-density plastic foam,

an airtight container enclosing said lamination,

means for pressurizing said container so that said layers of foam are pressurized to the desired degree of firmness,

said pressurized container having separately pressurized cells around the periphery thereof, the cells around the periphery being supplied with air at a higher pressure than the remaining portion of said container to provide firmer support at the edges of said container,

an open pore uniform foam layer on top of said pressurized container, and

a source of ventilating air connected to said open pore foam layer producing a flow of air from the top of said foam layer for patient ventilation.