Beds – Invalid bed or surgical support – Tiltable along a longitudinal axis
Reexamination Certificate
1997-02-18
2001-09-04
Trettel, Michael F. (Department: 3628)
Beds
Invalid bed or surgical support
Tiltable along a longitudinal axis
C005S710000, C005S715000
Reexamination Certificate
active
06282737
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for alternating the air pressure of a low air loss patient support system. More particularly, it relates to a bed having a frame with two sets of air bags mounted thereto, a gas source which is mounted in the frame of the bed to supply a flow of gas to the two sets of air bags without the necessity for a separate unit having a blower and controls to supply the air bags, means on each of the air bags for moving a patient supported thereon toward one side of the frame and then back toward the other side of the frame when gas is supplied to the first set of air bags and then to the second set of air bags, and means on the air bags for retaining the patient on the air bags when the patient is moved toward the respective sides of the frames. Such a bed can be used to advantage for the prevention of bed sores and the collection of fluid in the lungs of bedridden patients. Other devices are known which are directed to the same object, but these devices suffer from several problems. In particular, U.S. Pat. No. 3,822,425 discloses an air mattress consisting of a number of cells or bags, each having a surface which supports the patient formed from a material which is gas permeable but is non-permeable to liquids and solids. It also discloses an air supply for inflating the cells to the required pressure and outlets or exhaust ports to allow the escape of air. The stated purpose of the outlets is to remove condensed vapor for the cells or bags. The outlets on that mattress may be fitted with valves to regulate the air pressure in the cells as opposed to regulating the air pressure in the cells by controlling the amount of air flowing into the cells. However, the air bed which is described in that patent and which is currently being marketed under that patent is believed to have certain disadvantages and limitations.
For example, that bed has a single air intake coupler, located directly and centrally underneath the air mattress, for connection of the source of air. Access to this connection is difficult since one must be on their back to reach it. The location of the connection underneath the mattress creates a limitation in the frame construction because the air hose must pass between the bed frame members. The source of air to which the air hose is connected is a blower or air pump mounted in a remote cabinet which, because it must be portable, is mounted on casters. There are many times in actual use when the cabinet must be moved in order to wheel other equipment, such as I.V. stands, around it or for access to the patient. However, relocation of this blower unit by any significant distance requires disconnection of the air hose from the frame (inconvenient because of the location up underneath the frame) or the pendent control in order to avoid wrapping the air hose around the bed frame members. Of course, disconnection of the air hose results in the loss of air pressure in the air mattress, which is even less desirable.
Another disadvantage with that type of bed relates to the monitoring of patient body weight. When charting fluid retention and other parameters, the patient's body weight is monitored continuously. When a patient is bedridden, the only way to monitor body weight is to weigh both bed and patient, then subtract the weight of the bed. But when a portion of the bed hangs off of the bed, as the air hose does, and when the changes in weight being monitored are measured in ounces, it is very difficult to accurately chart the changes in body weight when the patient is on such a bed.
Further, the bed disclosed by that patent is limited in that only a finite amount of air can be forced or pumped into the air mattress. By eliminating the outlets described in that patent entirely, the air pressure in the bags can at least be maintained at that point which represents the maximum output of the source of gas. In the case of the bed described in that patent, if it is necessary to further increase the pressure in the air bags while the outlets are being used for their stated purpose, the only way to do so is to install a larger capacity blower in the cabinet. High air pressures may be necessary, for instance, to support obese patients. A larger capacity blower generally requires more power consumption and a higher capacity circuit which may not be readily available. Also, the larger the blower, the more noise it creates which is not desirable.
The limitations and disadvantages which characterize other previous attempts to solve the problem of preventing bed sores in bedridden patients are well characterized in English Patent No. 1,474,018 and U.S. Pat. No. 4,425,676.
The prior art also discloses a number of devices which function to rock a patient back and forth by the use of air pressure. For instance, U.S. Pat. Nos. 3,477,071, 3,485,240, and 3,775,781 disclose hospital beds with an inflatable device for shifting or turning a patient lying on the bed by alternately inflating and deflating one or more inflatable cushions. U.K. Patent Application No. 2,026,315 discloses a pad, cushion, or mattress of similar construction. German Patent DE 28 16 642 discloses an air mattress for a bedridden person or hospital patient consisting of three longitudinal inflatable cells attached to a base sheet, the amount of air forced into each cell being varied so as to alternately rock the patient from one side of the mattress to the other. However, none of those mattresses or devices is designed for use in a low air loss patient support system. Further, the U.K. and German patents, and U.S. Pat. Nos. 3,477,071 and 3,775,781, disclose devices consisting of parallel air compartments which extend longitudinally along the bed and which are alternately inflated and deflated. Such a construction does not allow the use of the device on a bed having hinged sections corresponding to the parts of the patient's body lying on the bed so that the inclination and angle of the various portions of the bed can be adjusted for the patient's comfort.
U.S. Pat. No. 3,678,520 discloses an air cell for use in a pressure pad which is provided within a plurality of tubes which project from a header pipe such that the air cell assumes a comb-like conformation when inflated and viewed from above. Two such air cells are enclosed within the pressure pad with the projecting tubes interdigitating, and air is alternately provided and exhausted from one cell and then the other. That device is not suitable for use on a bed having hinged sections corresponding to the parts of the patient's body lying on the bed so that the angle of inclination of the various portions of the bed can be adjusted for the patients comfort, nor is it capable of functioning in the manner described if constructed in the low air loss conformation.
A number of patents, both U.S. and foreign, disclose air mattresses or cushions comprised of sets of cells which are alternately inflated and deflated to support a patient first on one group of air cells and then the other group. Those patents include U.S. Pat. Nos. 1,772,310, 2,245,909, 2,998,817, 3,390,674, 3,467,081, 3,587,568, 3,653,083, 4,068,334, 4,175,297, 4,193,149, 4,197,837, 4,225,989, 4,347,633, 4,391,009, and 4,472,847, and the following foreign patents: G.B. Patent No. 959,103, Australia Patent No. 401,767, and German Patent Nos. 24 46 935, 29 19 438 and 28 07 038. None of the devices disclosed in those patents rocks or alternately moves the patient supported thereon to further distribute the patient's body weight over additional air cushions or cells or to alternately relieve the pressure under portions of the patient's body.
There are also a number of patents which disclose an inflatable device other than an air mattress or cushion but which also involve alternately supplying air to a set of cells and then to another set of cells. Those patents include U.S. Pat. Nos. 1,147,560, 3,595,223, and 3,867,732, and G.B. Patent No. 1,405,333. Of those patents, only the British patent discloses t
Quirk William H.
Trettel Michael F.
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