PATIENT SUPPORT APPARATUS

Abstract: A hospital bed for severly injured e.g. burned patients has a frame (120) receiving a fluid-inflatable support (140) for a patient to lie on, a fluid supply source (150) including a compressor (152) is in communication with the fluid support (140) and a detector (170) associated with the fluid support (140) monitors the degree of inflation thereof. Control devices such as valves, switches or the like are operatively associated with the fluid supply (150) and detector (170) to actuate the compressor (152) in response to a predetermined input from the detector (170), to keep the support (140) inflated to a degree providing adequate support for the patient.

Description: This invention relates to a fluid support device as disclosed in the US-A-3 866 606. Historically, hospital beds for patients have in general been conventional where, though adjustable as to height and attitude, a mattress-springs arrangement has been provided for receiving the patient thereon covered, of course, with appropriate bed clothing. Particular problems have developed in use of the conventional hospital beds where the patients, due to prolonged contact with the support surface in generally immobile conditions, have developed decubitus ulcers or bed sores, as a result of pressure points between the support surface and certain portions of the patient's body. Additionally, in the case of burn patients where the severity of the injury or wound was such that the patient was affected over a significant portion of his body, the conventional bed presented problems not only with the healing process due to contact between raw areas of the human body and the support, but also due to fluids exuding from the patient's body. In like fashion, other types of injuries and reasons for confinement have presented problems with the conventional hospital bed. In order to obviate some of the problems inherent with the conventional hospital bed, fluidized patient support structures have been developed as exemplified in US-A-3,428,973 in which a tank is provided, partially filled with a mass of granular material which is received atop a diffuser surface and is covered with a loose fitting flexible patient contact sheet or surface. Fluid, such as air, is provided in a plenum chamber beneath the diffuser surface and is forced through the diffuser surface for fluidization of the granular material, preferably ceramic spheres, with adequate force that a patient received on the flexible sheet is suspended on the fluidized bed. In this fashion, very gentle forces are imparted to the affected body portions of the patient, whereby the incidence of development of decubitus ulcers is reduced and whereby an individual experiencing trauma, such as produced by severe burns may rest comfortably. In similar fashion, a further fluidized patient support structure is disclosed in US-A-3,866,606 which structure has the same basic elements of that mentioned above with the addition of control means to cyclically fluidize the granular material, also preferably ceramic spheres. In a non-fluidized state, the patient settles into the mass of granular materials which becomes a rigid, body contoured, structure against which the patient's body may be placed in traction. In like fashion, the cyclic effect of fluidizing-rigidifying the mass of granular material permits variation in patient attitude, again towards variance of constant pressures on affected body portions and thus reduction of the incidence of development of decubitus ulcers. In both of the fluidized patient support systems described above, there is, for an adult patient, generally a minimum depth of about 12 inches (30 cm) of fluidized granular material located above a diffuser board to preclude any contact between the body of the patient and the diffuser board when the patient is in a sitting position on the bed. In other support systems, fluid support means may be provided as exemplified by air filled structures. Such fluid filled support structures may be an improvement over the conventional mattress supports, but are not considered to be as effective as the fluidized support systems noted above, though they are generally much less expensive, and thus more available for general use. In all of the structures mentioned above, it is important from a standpoint of comfort and effectiveness of support, that the patient have adequate support beneath the body to hold the body above an underside of the support structure. In other words, it is highly desirable that the patient not "bottom out" against an underlying rigid surface of the support system. One such air-filled support is disclosed in GB-A-1,398,544 which discloses a plural-compartment inflatable patient support means or mattress, no doubt in practice placed in or atop a support frame of some sort, and means for supplying fluid to the support means or mattress for inflating the same. By means of control valves, the different compartments of the support means are selectively and cyclically inflated and deflated, in order to impart a slow and smooth, continuous rocking movement on the patient. In any fluid supported system, and this includes the arrangement disclosed in GB-A-1,398,544, a number of problems may evolve resulting in inadequate fluid support of a patient. Such problems can result from inadequate fluid supply, leakage of fluid from the structure and the like. The support system embodying the present invention aims to provide an arrangement for sensing inadequate patient support and, depending on the fault, corrects it or alerts attending personnel to the problem which is not simply correctable by introduction of further fluid, reinflation or the like. It is an object of the present invention to provide an improved fluid patient support device which, for example, includes provision for ensuring adequate fluid for proper patient support. A fluid patient support device according to the present invention is provided with means to detect inadequate patient support and to initiate correction of same. A fluid patient support device embodying the present invention can have means to sense a patient settling too deeply into the support and means to vary the supply of further fluid thereto adequate to return the patient to a properly supported position. Starting from US-A-3 866 606 and according to the present invention, there is provided a fluid support device for a patient, comprising a support frame, an inflatable patient support means supported by the frame, and means for supplying fluid to the inflatable support means for support of a patient in a supine position thereon, characterised by sensor means associated with the inflatable support means for determining inadequate inflation of the support means when a patient is residing thereon, and control means operatively associated with the fluid supply means and the sensor means for receiving input from the sensor means that the support means is inadequately inflated, and for admitting further fluid to the support means responsive to the said input, to restore adequate inflation to the support means. Generally speaking therefore, the patient support device embodying the present invention comprises a support frame; a fluid patient support means supported by said frame; means for supplying fluid to said fluid support means for support of a patient in a supine position thereon; sensor means associated with said fluid support means for determining inadequate support of a patient residing thereon; and control means operatively associated with said fluid supply means and said sensor means for receiving input from said sensor means that support of the patient is inadequate and initiating further fluid supply to said support means responsive to said input for at least a predetermined period of time. More specifically, in a preferred arrangement, the sensor means is a pressure sensitive device, whereby should a patient settle into the fluid support means adequate to directly or indirectly apply a predetermined pressure on the detector means, the fluid supply means will be actuated by the control means to supply further fluid to the support means. In a fluid envelope environment, the sensor means may simply be located therebeneath. An air compressor can serve as a fluid supply means, when the sensor means can be operatively associated with a control means for the compressor to actuate or deactuate same. The compressor control means may take many forms, but preferably is operative in conjunction with the sensor means to continue to supply air to the support until the patient is properly supported whereby the sensor means is deactuated. Simultaneously, timer means may also be employed therewith, preset to actuate an alarm after a predetermined period of compressor operation, and/or set to operate for a predetermined period of time after deactuation of the sensor means, or the like. The preset time for actuation of an alarm would be greater than that normally required for reinflation or refluidization, and would be indicative of malfunction of the support means. The invention will be more readily understood from a reading of the following specification which is given by way of example only, and by reference to the accompanying drawings, wherein an embodiment of the invention is shown. In the drawings: Figure 1 is a schematic illustration of a preferred embodiment of a patient support system according to the present invention demonstrating proper patient support; Figure 2 is a schematic illustration of the embodiment of Figure 1 demonstrating improper patient support; Figure 3 is an electrical schematic diagram of a control system for a patient support system according to the present invention; and Figure 4 is a schematic illustration of a timing chart for the control arrangement as illustrated in Figure 3. As illustrated in Figures 1 and 2, a preferred embodiment of the support device for a supine patient is shown to be an air inflatable support means in the form of an inflatable mattress 140, with mattress 140 being manufactured of a flexible material such that upon inadequate inflation of same the weight of a patient residing thereon will collapse the mattress structure. Mattress 140 as illustrated in Figures 1 and 2, rests on a suitable base or frame 120, and is in operative association via a tubular conduit 144 with a fluid supply system 150, which preferably includes an air compressor 152. In general, according to the embodiment shown in Figures 1 and 2, once mattress 140 is inflated, air compressor 152 is deactuated and the degree of inflation may be maintained by appropriate valving, not shown. Additionally, in certain embodiments, mattress 140 could be provided with a plurality of small vent openings which could dictate continuous operation of air compressor 152. Should, however, adequate deflation of mattress 140 result, removing the necessary patient support, the patient will settle into mattress 140 and defeat the purpose of the system (see Figure 2). In order to monitor such an occurrence, a sensor means 170 is located beneath or within mattress 140 and is operatively connected to fluid supply means 150. Sensor means 170 may be pressure sensitive, or any other type sensing means that would indicate the inadequacy of inflation of mattress 140 as represented by proximity of a patient thereto. Hence, should the patient settle into mattress 140 adequately to actuate sensor 170, sensor 170 will provide input to a control means 180 associated with fluid supply means 150 in an arrangement as, for example, is illustrated in Figures 3 and 4, to cause actuation of compressor 152 adequate to return mattress 140 to a proper degree of inflation. In a most preferred embodiment, as schematically illustrated in Figure 3 a timer means 185 is associated with sensor means 170 and control means 180 to permit air compressor 152 to continue to operate for a predetermined period of time after removal of actuation pressure from sensor means 170. A full return to proper fluidization would thus be achieved. A further timer means 175 may also be employed in conjunction with sensor means 170 to become actuated simultaneously with control means 1 80 such that should air compressor 152 continue to operate for the full preset time of the timer means, such would indicate serious malfunction of the system and actuate an alarm 190 operatively associated with time 175. Attending personnel would then become alerted to a malfunction of the system requiring corrective action beyond normal refluidization. Figures 3 and 4, illustrate one preferred arrangement for an overall control system according to the present invention. Once sensor 170 is actuated e.g.by pressure above a present threshold value, output from same to a sample and hold circuit 172 causes circuit 172 to move to a higher value to provide output to a control valve 180 for actuation of same. Sample and hold circuit 172 thereafter continues to sample input from sensor 170, and so long as input is detected, circuit 172 holds at the higher value. Hold circuit 172 may further include a variable holding period feature which maintains the high value for a predetermined period of time after deactuation of sensor 170. Such time allows continued fluidization adequate to return to a normal support state and would be utilized in lieu of a timer 185 as mentioned above. Such variable time is indicated on line B of the timing chart of Figure 4. Simultaneously with actuation of control valve 180, the present timer means 175 if provided is actuated. Timer means 175 is operatively associated with alarm means 190 which may be visual and/or aural, and if the preset time lapses before resetting of timer means 175, such will indicate abnormal malfunction of the system and alarm 190 will be actuated to signal attending personnel. Timer means 175 is indicated on line E of the timing chart of Figure 4. In an embodiment as mentioned above where vent openings are included in the inflatable support, control means 180 may not be an off-on valve or switch means since fluid may be required continuously to replenish that escaping through the vent openings. Instead, control means 180 in the form of a valve would be located between compressor 152 and mattress 140 (shown in phantom in Figure 3), and would be further opened to permit greater fluid flow therethrough as required. Alternatively control means 180, though not shown, could be a potentiometer that increases or decreases the voltage applied to a motor associated with air compressor 152. In the embodiment shown in Figures 1 and 2, control means 180 would preferably be an on-off control means since under normal operations once the envelope is inflated, no further fluid would be admitted unless deflation occurs. In Figure 4, a suitable timing chart is illustrated. Line A represents sensor means 170, line B represents sample and hold circuit 172, line C represents a switching amplifier 173, line D represents the control means 180, line E represents the timer means 175 and line F the alarm 190. At level 0, each of the elements is in a deactivated state while at level 1 each is in an excited or actuated state. Hence as can be seen, once sensor 170 is actuated, all of the elements in the system are activated with the exception of alarm 190. Circuit 172 then remains at level 1 so long as sensor 170 is actuated and for a predetermined holding period thereafter, adequate to continue fluid supply for support of the patient well above sensor 170. Switching amplifier 173 remains on coincident with hold circuit 172 for amplification of the output signal therefrom. Control means 180 remains actuated (open, further open, higher fan speed, etc.) during the period of output from amplifier 173. As mentioned hereinabove, timer 175 is preset for a period of time that should be more than adequate for the system to return the support means to a proper supporting function, wherefore, should the time set on timer 175 lapse, such would indicate a more serious malfunction in the system. Alarm 190 would then be actuated to alert attending personnel. While mattress 140 is schematically illustrated as a single element, a plurality of individual air bags may be utilized as now appear in certain commercial systems and as illustrated in phantom as 140′, 140″, 140"' in Figure 1. In such systems, a number of air bags 10 to 15 for example may be employed along the length of a bed or frame. Also, pressures maintained in the plurality of bags may be the same in all bags or may vary along the length of the overall unit depending upon the anatomical body section in contact therewith. With the plural bag arrangement, one or more sensors 170 may be employed.

Claims: A fluid support device for a patient, comprising a support frame (120), an inflatable patient support means (140) supported by the frame, and means (150) for supplying fluid to the inflatable support means (140) for support of a patient in a supine position thereon, characterised by sensor means (170) associated with the inflatable support means (140) for determining inadequate inflation of the support means when a patient is residing thereon, and control means (180) operatively associated with the fluid supply means (150) and the sensor means (170) for receiving input from the sensor means that the support means (140) is inadequately inflated, and for admitting further fluid to the support means responsive to the said input, to restore adequate inflation to the support means (140). A fluid support device according to claim 1, wherein the inflatable patient support means (140) is an inflatable envelope. A fluid support device according to claim 1 or claim 2, wherein the sensor means (170) is a pressure sensitive device. A fluid support device according to claim 1, 2 or 3, further comprising timer means (175) operatively associated with the sensor means (170) and alarm means (190) operatively associated with the timer means for the timer means to be actuated simultaneously with the sensor means and to be deactuated upon cessation of operation of the fluid supply means (150), the timer means being operable to actuate the alarm means (190) after a predetermined period of operation of the fluid supply means. A fluid support device according to any of claims 1 to 4, wherein the inflatable patient support means (140) comprises a plurality of juxtaposed inflatable air bags (140', 140", 140"' etc.). A fluid support device according to claim 5, wherein respective sensor means is associated with each air bag (140', 140", 140"') and the control means is adapted to maintain the pressures the same in all the bags or to vary the pressures along the support means. A fluid support according to any of claims 1 to 6, wherein the control means (180) is operable to maintain the supply means (150) in a state of actuation so long as the sensor means (170) remains actuated. A fluid support according to any of claims 1 to 7, further comprising timer means (185) operatively associated with the sensor means (170) and the control means (180), the timer means being adapted to cause continued actuation of the fluid supply means (150) for a predetermined period of time following deactuation of the sensor means. A fluid support according to any of claims 1 to 3, further comprising alarm means (190) operatively associated with the control means (180), the alarm means being actuable after a predetermined period of time.

Inventors: PAUL, PATRICK R.D., PRICE, JAMES H.
Applicants: SSI MEDICAL SERVICES, INC.
Application year: 1986
Main classification: A61G7
IPC codes: A61G7, G05D16