Control of hospital bed chair egress configuration based on patient physiology

A patient support apparatus includes a frame having a patient support deck that is movable between a horizontal position to support a patient in a lying position and a chair egress position to support the patient in a sitting position. Depending upon a height of the patient, a lift system is operated to support the patient support deck relative to an underlying floor at different heights when the patient support deck is moved to the chair egress position. Depending upon a weight of the patient, at least one bladder of a mattress is either deflated or further inflated when the patient support deck is moved to the chair egress position and the patient is in the process of egressing from the patient support apparatus.

BACKGROUND

The present disclosure relates to patient support apparatuses, such as hospital beds. More particularly, the present disclosure relates to patient support apparatuses having mattress support decks that are movable between horizontal and chair egress positions.

Patient support apparatuses, such as hospital beds, that have articulated decks which move between horizontal and chair egress positions are known. The TOTALCARE® bed marketed by Hill-Rom Company, Inc. is one such bed. Beds are moved to the chair egress position to facilitate a patient's ability to egress from the bed and stand up in a manner similar to standing up from a chair. However, some patients may still have difficulty standing up from beds even when the beds are in the chair egress position. One reason for the difficulty, in some instances, is that the seating surface of the bed in the chair egress position may be too high or too low for the particular patient. In other instances, the difficulty may be created due to a seat region of a mattress being too soft such that the patient's immersion into the seat region presents an egress impediment. Accordingly, a need persists in improving bed features and functions that further facilitate patient egress from beds that have mattress support decks which are movable between horizontal positions and chair egress positions.

SUMMARY

A patient support apparatus, such as a hospital bed, has one or more of the features recited in the appended claims and/or the following features which, alone or in any combination, may comprise patentable subject matter:

A patient support apparatus may include a frame which may have a patient support deck. The patient support deck may be movable between a horizontal position to support a patient in a lying position and a chair egress position to support the patient in a sitting position. The patient support apparatus may also have a lift system that may be operable to support the patient support deck relative to an underlying floor at different heights. A control system may be provided to command operation of the lift system. The control system may receive data indicative of a height of the patient supported on the patient support deck. The control system may determine an elevation at which the lift system may support the patient support deck when the patient support deck is in the chair egress position based on the height of the patient.

The frame may further include a base and an upper frame above the base. The upper frame may support the patient support deck and the upper frame may be supported relative to the base by the lift system. The control system may include a user input that may be used by a caregiver to indicate the height of the patient. For example, the user input may comprise a touchscreen display. The control system may receive data indicative of the height of the patient from a remote computer. The data may be received by the control system via a wired datalink and/or a wireless datalink. The control system may command the lift system to support the patient support deck in the chair egress position at a higher elevation for taller patients and at a lower elevation for shorter patients.

The patient support apparatus may further have a mattress supported on the patient support deck. The mattress may have at least one inflatable bladder in a region of the mattress that supports the patient's buttocks when the patient support deck is in the chair egress position supporting the patient in the sitting position. The control system may have a pneumatic control system portion that may be operable to inflate and deflate the at least one inflatable bladder. The control system may determine whether to deflate the at least one inflatable bladder when the patient support deck is in the chair egress position based on a weight of the patient. In some embodiments, the frame may include at least one sensor, such as a load cell, that provides a signal to the control system indicative of the weight of the patient. Alternatively or additionally, the control system may receive data indicative of the weight of the patient from a remote computer.

According to this disclosure, the control system may determine whether to further inflate the at least one inflatable bladder when the patient support deck is in the chair egress position based on the weight of the patient. For example, the at least one inflatable bladder may be deflated when the patient support deck is in the chair egress position supporting the patient in the sitting position and the patient's weight is below a threshold amount of weight. On the other hand, the at least one inflatable bladder may be further inflated when the patient support deck is in the chair egress position supporting the patient in the sitting position if the patient's weight is above the threshold amount of weight.

In some embodiments, the control system may include a patient position monitoring system to monitor a position of the patient on the patient support deck. The control system may determine whether to deflate the at least one inflatable bladder when the patient support deck is in the chair egress position based on the weight of the patient and based on the position of the patient. For example, if the weight of the patient is below a threshold weight, then the control system may signal the pneumatic control system portion to maintain inflation of the at least one inflatable bladder if the patient position monitoring system indicates that the patient is reclined on the patient support deck when the patient support deck is in the chair egress position. On the other hand, if the weight of the patient is below the threshold weight, then the control system may signal the pneumatic control system portion to deflate the at least one inflatable bladder if the patient position monitoring system indicates that the patient is moving toward egressing from the patient support deck when the patient support deck is in the chair egress position. In some embodiments, if the weight of the patient is below the threshold angle, then the control system may signal the pneumatic control system portion to re-inflate the at least one inflatable bladder after the patient has egressed from the patient support deck by a threshold amount as determined by the patient position monitoring system.

According to this disclosure, therefore, a patient support apparatus may have a frame that may include a patient support deck. The patient support deck may be movable between a horizontal position to support a patient in a lying position and a chair egress position to support the patient in a sitting position. A mattress may be supported on the patient support deck. The mattress may have at least one inflatable bladder in a region of the mattress that supports the patient's buttocks when the patient support deck is in the chair egress position supporting the patient in the sitting position. The patient support apparatus may further have a control system that may be operable to control the inflation and deflation of the at least one inflatable bladder. The control system may receive data indicative of a weight of the patient supported on the patient support deck. The control system may operate to further inflate the at least one inflatable bladder when the patient support deck is in the chair egress position and the weight of the patient is above a threshold weight. The control system may operate to deflate the at least one inflatable bladder when the patient support deck is in the chair egress position and the weight of the patient is below the threshold weight.

The weight of the patient may be communicated to the control circuitry by at least one of a remote computer and a scale system coupled to the frame of the patient support apparatus. In some embodiments, the control system may include a patient position monitoring system to monitor a position of the patient on the patient support deck. If the weight of the patient is below the threshold weight, then the control system may operate to maintain inflation of the at least one inflatable bladder if the patient position monitoring system indicates that the patient is reclined on the patient support deck when the patient support deck is in the chair egress position. If the weight of the patient is below the threshold weight, then the control system may operate to deflate the at least one inflatable bladder if the patient position monitoring system indicates that the patient is moving toward egressing from the patient support deck when the patient support deck is in the chair egress position.

DETAILED DESCRIPTION

According to this disclosure, a patient support apparatus, such as an illustrative hospital bed10, has lift system features and functions and/or mattress pneumatic control system features and functions that assist a patient in standing up from the bed10when the bed10is in a chair egress mode. Depending upon a patient's height and/or weight, the lift system and/or pneumatic control system are operated differently during the chair egress mode as will be discussed in further detail below.

Illustrative bed10is a so-called chair bed that is movable between a bed position as shown inFIG. 1and a chair egress position as shown inFIG. 2. However, the teachings of this disclosure are applicable to other types of patient support apparatuses such as stretchers, motorized chairs, operating room (OR) tables, and specialty surgical tables such as orthopedic surgery tables, examination tables, and the like.

Referring now toFIGS. 1 and 2, hospital bed10provides support to a patient (not shown) lying in a horizontal position when bed10is in the bed position shown inFIG. 1and hospital bed10supports the patient in a sitting position such that the patient sits on bed10with the patient's feet positioned on an underlying floor when bed10is in the chair egress position shown inFIG. 2. Thus, the chair egress position is often used by patients and caregivers to help patients egress or exit the hospital bed10. Hospital bed10includes a frame20that supports a mattress22as shown inFIGS. 1 and 2. Bed10has a head end24and a foot end26.

Frame20includes a base28and an upper frame30coupled to the base28by a lift system32. Lift system32is operable to raise, lower, and tilt upper frame30relative to base28. Hospital bed10further includes a footboard45at the foot end26and a headboard46at the head end24. Footboard45is removed prior to bed10being moved into the chair egress position as shown inFIG. 2. Base28includes wheels or casters29that roll along the floor as bed10is moved from one location to another.

Illustrative hospital bed10has four siderail assemblies coupled to upper frame30: a patient-right head siderail assembly48, a patient-right foot siderail assembly18, a patient-left head siderail assembly50, and a patient-left foot siderail assembly16. Each of the siderail assemblies16,18,48, and50is movable between a raised position, as the left foot siderail assembly16is shown inFIG. 1, and a lowered position, as the right foot siderail assembly18is shown inFIG. 1. Siderail assemblies16,18,48,50are sometimes referred to herein as siderails16,18,48,50.

The left foot siderail assembly16is similar to the other siderail assemblies18,48,50, and thus, the following discussion of the left foot siderail assembly16is equally applicable to the other siderail assemblies18,48,50unless specifically noted otherwise. The left foot siderail16includes a barrier panel52and a linkage56. Linkage56is coupled to the upper frame30and is configured to guide barrier panel52during movement of the foot siderail16between the raised and lowered positions. Barrier panel52is maintained by the linkage56in a substantially vertical orientation during movement of siderail16between the raised and lowered positions. The barrier panel52includes an outward side58, an oppositely facing inward side59, a top portion62, and a bottom portion64.

A graphical user interface66is coupled to the outward side58of barrier panel52for use by a caregiver (not shown). The inward side59faces opposite the outward side58. As shown inFIG. 2, another user interface67is coupled to the inward side59for use by the patient. In the illustrative embodiment, user interface66comprises a touchscreen display. Also in the illustrative embodiment, a separate caregiver user interface65is provided on the outward side58of barrier panel52. User interface65includes a variety of buttons, such as membrane switches, for example, that are used to control various bed functions. Additional details of user interface65are provided in U.S. application Ser. No. 12/891,909 which is titled “Hospital Bed with Chair Lockout,” which was filed Sep. 28, 2010, and which is hereby incorporated by reference herein. For purposes of this disclosure, however, it is notable that user interface65includes a chair egress mode button69as shown generically inFIGS. 1 and 2.

Mattress22includes a top surface34, a bottom surface (not shown), and a perimeter surface36as shown inFIGS. 1 and 2. The upper frame30carries a mattress support deck38of frame20that engages the bottom surface of mattress22. The support deck38, as shown for example inFIG. 2and as shown diagrammatically inFIGS. 3 and 4, includes a head section40, a seat section42, a thigh section43and a foot section44. Each of sections40,43,44is movable relative to upper frame30. For example, in a first embodiment, head section40pivotably raises and lowers relative to seat section42whereas foot section44pivotably raises and lowers relative to thigh section43. Additionally, thigh section43articulates relative to seat section42. Also, in the illustrative embodiment ofFIGS. 1 and 2, foot section44is extendable and retractable to change the overall length of foot section44and therefore, to change the overall length of deck38. For example, in the illustrative embodiment, foot section44includes a main portion45and an extension47as shown inFIG. 1. In some embodiments, seat section42is also movable relative to upper frame30such as by pivoting and/or translating relative to upper frame30.

As bed10moves from the bed position to the chair egress position, foot section44lowers relative to thigh section43and shortens in length due to retraction of the extension47relative to main portion45. As bed10moves from the chair egress position to the bed position, foot section44raises relative to thigh section43and increases in length due to extension of the extension47relative to main portion45. Thus, in the chair egress position, head section40extends generally vertically upwardly from upper frame30and foot section extends generally vertically downwardly from thigh section43as shown inFIG. 2and as shown diagrammatically inFIGS. 3 and 4. In the bed position, mattress support deck38and upper frame30are in a horizontal position.

As mentioned previously, lift system32is operable to raise, lower, and tilt upper frame30relative to base28. In the illustrative embodiment, lift system32includes a set of head end lift arms78and a set of foot end lift arms80(only one of which can be seen inFIG. 1) to accomplish the raising, lowering and tilting functions of upper frame30relative to base28. As bed10moves from the horizontal bed position ofFIG. 1to the chair egress position ofFIG. 2, motors or actuators (not shown) are operated to move arms78,80to lower upper frame30toward base20if frame30is in a raised position initially.

In the illustrative example, bed10has four foot pedals84coupled to base28on each side of base28. A first of pedals84is depressed to raise upper frame30relative to base28, a second of pedals84is used to lower frame30relative to base28, a third of pedals84is used to raise head section40relative to upper frame30, and a fourth of pedals84is used to lower head section40relative to upper frame30. In other embodiments, foot pedals84are omitted.

It should be appreciated by those skilled in the art that bed10includes various actuators or motors (not shown) to move lift arms78,80of lift system32, to move sections40,43,44relative to upper frame30, and to move section42, as well, in those embodiments in which section42moves relative to upper frame30. For example, it is well known in the hospital bed art that electric drive motors with various types of transmission elements including lead screw drives and various types of mechanical linkages may be used to cause relative movement of portions of patient support apparatuses including raising, lowering, or tilting one portion of a bed relative to another. It is also well known to use pneumatic or hydraulic actuators to actuate and/or move individual portions of patient support apparatuses. As a result, the terms “actuator(s), “motor(s),” “lift system,” “elevation system” and similar such words as used in the specification and in the claims, therefore, are intended to cover all types of mechanical, electromechanical, hydraulic and pneumatic mechanisms, including manual cranking mechanisms of all types, for raising or lowering or tilting portions of patient support apparatuses, such as illustrative hospital bed10, relative to other portions. For example, lift systems using scissors linkage arrangements or using vertically oriented telescoping structures, such as hydraulic cylinders or jack screws, are within the scope of this disclosure. As another example, electrically powered linear actuators to articulate deck sections42,43,44and to pivot arms78,80are also within the scope of this disclosure.

Depending upon the height of the patient, the lift system32is operated so that a seating surface of deck38, which for purposes of this discussion is arbitrarily defined by the upper surfaces of seat and thigh sections42,43, are moved to various target heights above the underlying floor when deck38is moved into the chair egress position. In other embodiments, a hospital bed may have only three deck sections such that the upper surface of only the middle or seat section may be considered to arbitrarily define the seating surface when the 3-section deck is moved into a chair egress position. To illustrate this general concept, inFIG. 3, a tall patient100is shown adjacent bed10and lift system32has been controlled so that the seating surface is located at a first height, h1, above the floor and, inFIG. 4, a short patient102is shown adjacent bed10and lift system32has been controlled so that the seating surface is located at a second height, h2, above the floor. Height h1is the programmed height for the tall patient and is greater than h2which is programmed for the short patient. Thus, for tall patients, lift system32is operated to place upper frame30and sections42,43at an elevation which is higher than for short patients. While patients100,102are shown next to bed10in FIGS.3and4, it should be understood that bed10is typically moved into the chair egress position while the patients are supported by mattress22on deck38.

In some embodiments, the height of the seating surface generally corresponds to the popliteal height of the corresponding patient. The popliteal height is the height from the floor, when the patient's feet are placed flat on the floor, up to the patient's popliteal, which is the part of the leg that bends behind the knee. The illustrative heights h1and h2are simply two discrete elevations corresponding to patients having two discrete heights. However, it is contemplated by this disclosure that a spectrum of seating surface heights is achievable when bed10is in the chair egress position depending upon the height of the associated patient.

Because male and female adult patient heights fall generally into respective Gaussian distributions, lift system control algorithms according to this disclosure may account for a large percentage, such as 90% for example, of the patient population such that a maximum seating surface height corresponds to patients at the 95thpercentile in height and such that the minimum seating surface height corresponds to patients at the 5thpercentile in height. A linear correlation, or other mathematical correlation if desired or appropriate, is then used to establish the seating surface height when bed10is in the chair egress position. This is not to say that algorithms that account for a greater percentage or lesser percentage than 90% of the height of any given patient population are outside the scope of this disclosure. In the United States, however, it is generally known that the popliteal height of a male at the 95thpercentile of height is about 490 millimeters (mm) (or 19.3 inches) and the popliteal height of a female at the 5thpercentile of height is about 355 mm (or 14.0 inches). In some embodiments, therefore, lift system32is operable to place the seating surface at heights between about 19.3 inches and about 14.0 inches depending upon the height of the associated patient.

In some embodiments, it is assumed that there is a linear or proportional correlation between overall patient height and the popliteal height. In such embodiments, a straight correlation curve or equation results for determining seating surface height when bed10is in the chair egress position. In some embodiments, a look up table may be programmed into the algorithm rather than using a curve or formula. In some contemplated embodiments, different correlation curves, equations, and/or look up tables may be programmed for male patients and female patients, if desired, based on the anthropometric data for these two populations. Alternatively or additionally, it is also within the scope of this disclosure for different correlation curves to be programmed based on a comparison of popliteal height to overall height for different races and/or ethnicities. In such embodiments, in addition to the height data, a caregiver either enters data regarding the patient's sex, race, and/or ethnicity into the control system of bed10or such data is transmitted to the control system of bed10from a remote computer device, such as a computer device of an electronic medical records (EMR) system.

In some embodiments, an offset from the popliteal height may be included as part of the algorithm for determining seating surface height when bed10is in the chair egress position. For example, having the seating surface 1 or 2 inches, or more, below the popliteal height when bed10is in the chair egress position so that the patient can bend their legs at the knee more than 90 degrees prior to standing up from bed10may be desired in some instances. In other instances, it may be desired to have the seating surface 1 or 2 inches, or more, above the popliteal height when bed10is in the chair egress position so that the patient does not need to bend their legs at the knee quite as much while standing up from the bed10. One such instance may occur, for example, if the patient has had knee surgery and is unable to bend their legs at the knee more than 90 degrees. The offset from the popliteal height may be selectable on graphical user interface66in some embodiments.

In the discussion above, the height or elevation of the seating surface from the floor was said to be the arbitrarily chosen distance of interest. However, the height above the floor of some other arbitrary reference point or plane on bed10, when bed10is in the chair egress position, may be monitored or calculated just as well. For example, the top or bottom surface of upper frame30could be chosen as the reference point or plane. Furthermore, the distance of the reference point or plane of some portion of the upper frame30or deck38above some other reference point or plane on base28, rather than the floor, may be the distance that is monitored or calculated in some embodiments. Regardless of whether the position of upper frame30relative to base28is controlled based on patient height, or whether some other distance is controlled, the end result is that the seating surface height above the floor is varied based on patient height.

The actuators or motors that move lift arms78,80of lift system32have sensors, such as rotary potentiometers in some embodiments, and the signals from the sensors are used to determine the height of upper frame30relative to base. In other embodiments, the sensors may include accelerometers or inclinometers on lift arms78,80which provide signals indicative of the angle of lift arms78,80relative to vertical or horizontal or relative to some other reference plane. Based on the information regarding the angle of lift arms78,80, the height of upper frame30above base28can be determined. Additional sensors may be provided on base28and/or upper frame28to indicate whether these portions of bed are at an angle other than horizontal such as will be the case with base28when bed10is being pushed up or down a ramp.

Referring now toFIG. 5, a Select Patient Height screen90shown on graphical user interface66has a feet up button92, a feet down button94, an inch up button96, and an inch down button98which are touched by a caregiver to enter a patient's height into the control system of the hospital bed. In the illustrative example, a bar graph104with a slider icon106is also shown on screen90. Icon106appears on graph104at the position corresponding to the height selected by the caregiver using buttons92,94,96,98. In some embodiments, the caregiver is able to touch and drag icon106along graph104to change the height setting.

In the illustrative embodiment, a Ft/in button108and a M/cm button110is provided to permit toggling between feet/inch units and meter/centimeter units. In the illustrative example, feet/inch units have been chosen so the patient's height in feet and inches are shown on screen90. The feet value is shown between buttons92,94and the inch value is shown between buttons96,98. Also, the gradations on graph104are in feet/inches. In response to selecting M/cm button110, a meter value is shown between buttons92,94, a centimeter value is shown between buttons96,98, and the gradations on graph104switch to meters/centimeters.

After the caregiver selects the patient's height using buttons92,94,96,98or slider106, the user double taps a blank area on screen90in some embodiments to store the selected height in memory of the control system of bed10. In other embodiments, screen90includes an enter button that is touched for this purpose. Alternatively or additionally, if the caregiver does not touch any of buttons92,94,96,98,108,110or slider106for a threshold amount of time, such as 10 or 15 seconds, for example, then the height value shown on screen90is stored in memory of the control system.

It is also contemplated by this disclosure that, in some embodiments, the patient's height data and/or weight data is transmitted to bed10from a remote computer or system, such as a computer112of an electronic medical records (EMR) system, via communication infrastructure114and data links116,118as shown diagrammatically inFIG. 6. At bed10, the patient's height data is stored in memory122of control circuitry120regardless of whether the height data is transmitted to bed10or whether a caregiver has entered the data on screen90. In the illustrative embodiment, bed10includes a scale system136as will be discussed in further detail below. The scale system136is able to measure the patient's weight and then the measured weight is stored in memory122of control circuitry120. In the illustrative example, scale system136also functions as a patient position monitoring (PPM) system and so is indicated as scale/PPM system136inFIGS. 11-13. In other embodiments, weight data is transmitted to bed10from a remote computer112as previously mentioned. In other contemplated systems, computer112is part of a nurse call system, a physician ordering system, an admission/discharge/transfer (ADT) system, or some other system used in a healthcare facility. Communication infrastructure114inFIG. 6is illustrated diagrammatically and is intended to represent all of the other hardware and software that comprises a network of a healthcare facility.

Data links116,118are wired communications links and/or wireless communication links. For example, communications link118, in some embodiments, comprises a cable that connects bed10to a wall mounted jack that is included as part of a bed interface unit (BIU) or a network interface unit (NIU) of the type shown and described in U.S. Pat. Nos. 7,538,659 and 7,319,386 and in U.S. Patent Application Publication Nos. 2009/0217080 A1, 2009/0212925 A1 and 2009/0212926 A1, each of which are hereby expressly incorporated by reference herein. In other embodiments, communications link118comprises wireless signals sent between bed10and a wireless interface unit of the type shown and described in U.S. Patent Application Publication No. 2007/0210917 A1 which is hereby expressly incorporated by reference herein. Communications link116also comprises one or more wired links and/or wireless links as previously noted.

In some embodiments, bed10includes a pneumatic control system124that controls inflation and deflation of various air bladders or cells of mattress22. As shown diagrammatically inFIGS. 7-9and11-13, mattress22of bed10has a set of head zone bladders126, a set of seat and thigh zone bladders128(sometimes referred to herein as just “seat zone bladders128”), and a set of foot zone bladders130. Bladders126,128,130are coupled to the pneumatic control system124via respective pneumatic lines132,134,136which comprise flexible tubes or hoses, for example. Pneumatic control system124is illustrated diagrammatically and is intended to represent the various components such as one or more air sources including compressors, blowers, fans, pressure reservoirs, and the like; one or more manifolds; one or more valves; one or more pressure sensors; and the associated circuitry that controls the inflation and deflation of bladders126,128,130. Pneumatic control system124is in electrical communication with the main control circuitry120of bed10as indicated diagrammatically by communications link142. In the illustrative example, communications link142is a bidirectional communications link.

According to this disclosure, as deck38moves into the chair egress position, head section40raises as indicated by arrow138inFIG. 7and foot section44lowers as indicated by arrow140inFIG. 7. Of course, the portions of mattress22supported by deck sections40,44raise and lower along with the respective deck sections40,44in directions138,140, respectively. As foot section44lowers, pneumatic control system124is operated to deflate the set of foot zone bladders130such that air is evacuated from bladders130via line136as shown inFIG. 7. In some embodiments, pressure adjustments are also made in seat zone bladders128and/or head zone bladders126. For example, bladders128are further inflated in some embodiments to prevent or lessen the chance of the patient bottoming out on the seat section42of deck38. Bottoming out refers to the situation in which a patient completely crushes or deforms a mattress bladder to the extent that the patient feels the underlying deck section.

The state of inflation and deflation of bladders126,128,130shown inFIG. 7corresponds to the situation in which bed10is moved to the chair egress position and the patient intends to remain sitting in the bed10for some period of time. When it is time for the patient to stand up from bed10, the caregiver presses or touches chair egress button69of user interface65to activate the chair egress mode of bed10. Depending upon the weight of the patient, the pneumatic control system124operates either to deflate seat zone bladders128for lighter patients as shown inFIG. 8or to further inflate seat zone bladders128for heavier patients as shown inFIG. 9. Thus, to further illustrate this general concept, inFIG. 8, a light weight patient200is shown adjacent bed10and system124has been operated so that seat zone bladders128are deflated via line134and, inFIG. 9, a heavy weight patient202is shown adjacent bed10and system124has been operated so that seat zone bladders128are further inflated via line134.

A block diagram illustrative of the algorithm executed by the control system of bed10to determine whether to deflate or further inflate bladders128in response to the activation of chair egress button69is shown inFIG. 10. The control circuitry120, pneumatic control system124, and scale/PPM system136, either individually or together, are considered to be a control system of bed10according to this disclosure. The control system of bed10includes additional circuitry in some embodiments, such as power control circuitry, battery recharging circuitry, and so forth. Thus, a control system of a patient support apparatus, such as bed10, is considered to be some or all of the electrical hardware and software that controls, operates, or is associated with any of the functions of the patient support apparatus.

The algorithm ofFIG. 10begins as a result of the caregiver pressing or activating the chair egress button69as indicated at block150. After the button69is pressed, the control system of bed10reads the patient weight as indicated at block152. The control system then compares the patient's weight to a threshold value, X, as indicated at block154. If the patient's weight is above the threshold amount of weight, then bladders128are further inflated as indicated at block156. If the patient's weight is equal to or below the threshold amount of weight, then bladders128are deflated as indicated at block158. Regardless of whether bladders128are deflated or further inflated in response to the chair egress button69being activated, the result is that the surface on which the patient is sitting just prior to egressing from bed10is made firmer, thereby making it easier for the patient to get up out of the bed. Thus, the patient's immersion into the seat region, which as mentioned previously presents an egress impediment in some prior art beds, is lessened or substantially eliminated by further inflating bladders128or by deflating them.

The threshold amount of weight for determining whether to deflate or further inflate bladders128may be in the range of 200 to 300 pounds in some embodiments, for example. Thresholds that are greater than or lesser than this range are within the scope of this disclosure. The threshold amount of weight is at the discretion of the system designer and/or programmer and is dependent upon a number of factors including, for example, whether there is a base foam layer or some other cushioning element beneath or atop bladders128. In any event, lighter patients are thought to be able to withstand the bottoming out that occurs as result of deflating bladders128better than heavier patients because lighter patients will have less weight bearing upon the skin tissue of the buttocks region which reduces the chances that lighter patients will develop pressure sores or decubitus ulcers when supported on a hard surface. In some embodiments, for heavier patients, bladders128may remain at their current level of inflation rather than being further inflated.

Referring now toFIGS. 11-13, a further inflation control feature of bed10will be described for lighter weight patients200. Before describing this additional inflation control feature, it is worth noting that upper frame30of bed10, in the illustrative example, includes a lift frame160and a weight frame162which is supported relative to the lift frame160by a set of load cells164. InFIGS. 11-13, two loads cells164are illustrated diagrammatically. However, a common arrangement for hospital beds is to have four load cells arranged at the corners of an imaginary rectangle, for example, and such an arrangement is certainly within the scope of this disclosure. Each of the load cells164include a mass of material that deflects under the weight of the load carried by weigh frame162, and the deflection is sensed by one or more strain gages mounted to the mass of material.

The one or more strain gages of load cells164are electrically coupled to the scale/PPM system by lines166. Thus, the current or voltage sensed on lines166correlates to the amount of deflection of load cells164and therefore, to the amount of weight supported by load cells164. By subtracting out the tare weight (i.e., the weight of everything supported by load cells164other than the patient), the patient's weight can be determined. Furthermore, based on the individual readings from the load cells, the position of the patient on bed10can be determined. See, for example, U.S. Pat. No. 7,253,366 which shows and describes such a scale/PPM system and which is hereby expressly incorporated by reference herein. In some contemplated embodiments, while the patient is supported on bed10, the signals from the load cells164are used to determine a position of the patient's center of gravity relative to a plane passing through the load cells164. In some embodiments, other types of weight sensors, such as force sensitive resistors (FSR's), capacitive sensors, linear variable displacement transducers (LVDT's), or the like are used in lieu of, or in addition to, load cells164to provide signals for determining a patient's weight or position.

As shown inFIG. 11, when a patient is reclining on mattress22, bladders128are inflated. As the patient begins to egress from bed10and moves or leans toward the foot end of the seating surface, as shown inFIG. 12, the scale/PPM system136senses this movement based on the signals from load cells164and bladders128are deflated by the pneumatic control system124. When the patient begins to stand up from bed10and transfers weight off of bed10, as shown inFIG. 13, this is also sensed by the scale/PPM system136based on signals from load cells164and bladders128are re-inflated. By re-inflating bladders128as the patient stands up, a softer seating area is created in the event that the patient inadvertently falls back onto the bed10during the egress process. This protects the patient from falling back down onto a hard seating surface. Once a threshold amount of time, such as 10 to 30 seconds, after the re-inflation of bladders128has elapsed, the bladders128are again deflated to ready the bed10for the patient's return. Thus, after the threshold amount of time, the patient is assumed to have successfully egressed from the bed10, is standing up, and is no longer at risk of falling back down onto bed10.

The deflation, re-inflation, and then re-deflation of bladders128just described is contemplated as being a feature of bed10that is used with lighter weight patients. For the heavier patients, bladders128are already inflated and so if the heavier patients fall back down onto the bed10during egress, they will not encounter the type of hard seating surface of the underlying deck sections42,43. In some embodiments, the deflation, re-inflation, and then re-deflation of bladders128occurs only after chair egress button69has been pressed or otherwise activated. In other contemplated embodiments, the deflation, re-inflation, and re-deflation function occurs automatically based on the movement of the patient sensed by the scale/PPM system136. In still further embodiments, after bladders128have been deflated and re-inflated during the egress process, the bladders128remain re-inflated for the patient's return to bed10.

Although certain illustrative embodiments have been described in detail above, many embodiments, variations and modifications are possible that are still within the scope and spirit of this disclosure as described herein and as defined in the following claims.