Patient transfer device

A patient transfer device includes a mat, with an upper side and a gas permeable lower side. The mat includes a chamber between its upper and lower sides, which is operable to be in fluid communication with an air source such that when air flows into the mat, the air will flow into the chamber and through the gas permeable lower side to form an air film between the mat and a surface on which the mat is supported at its lower side. In addition, the lower side of the mat is substantially planar when the mat is inflated. A system for controlling the inflation of the mat may be used that automatically adjusts for the inflation of the mat during patient transfer.

BACKGROUND AND TECHNICAL FIELD OF THE INVENTION

The present invention pertains to devices for moving patients and, more particularly, to devices that use air to transfer a patient.

Non-ambulatory patients in a patient facility, such as a hospital or a nursing home, present substantial challenges when such patients must be moved from one location to another. A patient may, for example, need to be moved from a hospital bed to a stretcher and then from the stretcher to a treatment location, such as a surgical table in an operating room. Following treatment, the reverse patient handling sequence may occur; i.e.: the patient is moved from the surgical table, which remains in the operating room, to a stretcher which travels to the patient's hospital room, and then from the stretcher back onto the bed in the hospital room.

In some situations it is preferable that a patient be handled in a manner that minimizes handling or jostling of the patient, for example, in the case of a patient being returned to a hospital room following surgery. The same challenge of moving a patient with minimum handling exists in non-surgical settings as well. The bariatric patient is a prime and very common example. When such a patient is obese, transfers present difficulties for both the patient and the care facility staff. While obese patients represent an extreme end of the spectrum, it should be understood that making any transfer, lateral or otherwise, of any patient or adjustment to a patient's position can induce stress and/or strain and potential injury to a caregiver.

A drawback to some current patient handling procedures, such as sliding the patient across the patient support surface, is that, even with the best intentioned and caring of staff, the patient very often suffers substantial discomfort. The simple act of sliding a patient over a flat surface can be very painful to a patient who has had surgical incisions that are not yet healed, for example, or for patients who have skin lesions or ulcers.

An attempt has been made to overcome the above described problems by the use of an air mattress or pallet onto which the patient is placed while in bed and which is then placed onto a stretcher. A problem common to most of such devices, however, is that invariably the air mattress has the general characteristic of a balloon in the sense that when one area is indented another remote area will bulge. Further, they tend to provide little lateral stability. If, for example, a stretcher carrying an obese person makes a sharp turn during a trip to or from a treatment location, such an obese person may tend to roll or shift laterally toward the edge of the mattress, which could result in a patient rolling off the mattress.

Further, these mattresses require a large volume of air and flow rate to keep them inflated and operational. They also take time to fill and to become operational given their large volumes. Hence, to speed up the process the blowers that inflate the mattresses tend to be large and produce a lot of noise and also another undesirable by-product—heat. If the air into the mattress is too warm, the patient can become uncomfortable. These air pallets also tend to be bulky and may create a cleaning challenge because if body fluids (liquids) are released and flow under the mattress the holes in the bottom of the mattress will allow the liquid to flow into the mattress—likely requiring the disposal of the mattress.

Therefore there is a need for a new patient transfer device that facilitates the movement of a patient with minimal jostling of the patient and also that provides enhanced infection control. Further, a more compact transfer device is desirable that does not require the same volume of air or flow rate associated with prior art air bearing pallets, thus reducing the undesirable by-products of heat and noise that is associated with prior art air bearing pallets.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a transfer mat that is adapted to transfer a patient using an air film and configured so that it can be operated at a significantly lower air flows than associated with prior art air bearing pallets. The mat also may be configured to provide enhanced infection control.

In one form of the invention, a patient transfer mat includes upper and lower sides and a chamber between its upper and lower sides, which is operable to be in fluid communication with an air source such that when air flows into the mat, the air will flow into the chamber and through a gas permeable portion of the lower side of the mat to form an air film between the mat and a surface on which the mat is supported at its lower side. The mat is configured so that the lower side of the mat remains substantially flat or planar even when the mat is inflated.

In another form of the invention, a patient transfer mat includes a chamber between its upper and lower sides, which is operable to be in fluid communication with an air source such that when air flows into the mat, the air will flow into the chamber and through a gas permeable portion of the lower side of the mat to form an air film between the mat and a surface on which the mat is supported at its lower side. The mat is configured so that the thickness of the mat remains substantially uniform across its width and length even when inflated.

In yet another form of the invention, a patient transfer mat includes a chamber between its upper and lower sides, which is operable to be in fluid communication with an air source such that when air flows into the mat, the air will flow into the chamber and through a gas permeable portion at the lower side of the mat to form an air film between the mat and a surface on which the mat is supported at its lower side. The mat is configured so that the maximum thickness of the mat remains less than 1″, optionally less than ½″, and optionally about ¼″ when inflated.

According to yet another form of the invention, a patient transfer mat includes a chamber between its upper and lower sides, which is operable to be in fluid communication with an air source such that when air flows into the mat, the air will flow into the chamber and through a gas permeable portion of the lower side of the mat to form an air film between the mat and a surface on which the mat is supported at its lower side. The mat is configured so that when a patient is lying on the mat and the mat is inflated, the upper surface will be raised less than 3″, optionally less than 2″, and optionally less than 1″ off the surface supporting the mat to thereby better stabilize a patient over the prior art devices. Further, in some embodiments, the mat may be configured so that when inflated the upper surface raises less than 1″, optionally less than ½″, and optionally less than ¼″ off the support surface.

In yet another form of the invention, a patient transfer mat includes a chamber between its upper and lower sides, which is operable to be in fluid communication with an air source such that when air flows into the mat, the air will flow into the chamber and through a gas permeable portion of the lower side of the mat to form an air film between the mat and a surface on which the mat is supported at its lower side. The mat's upper and lower sides are joined to an intermediate layer that provides a substantially continuous connection between the upper and lower sides so that when air flows into the chamber the upper and lower sides remain substantially flat and uniformly spaced. In this manner, the mat will not tend to billow, taco or hot dog—and instead, will retain its generally flat shape when inflated.

According to another form, of the invention, a patient transfer mat includes a chamber between its upper impermeable side and lower gas permeable side with a volume of less than 1 cubic foot, which is operable to be in fluid communication with an air source such that when air flows into the mat, the air will flow into the chamber and through the lower gas permeable side of the mat to form an air film between the mat and a surface on which the mat is supported at its lower side.

In any of the above mats, the mat is configured to generate an air film sufficient to move a patient supported on the mat with a flow rate into the chamber in a range of 7-10 cubic feet per minute.

In any of the above mats, the mat includes an impermeable upper side formed by a gas and liquid impermeable barrier so that air in the chamber will not be directed from the upper side of the mat. Similarly the lower side may be formed by a gas permeable barrier and optionally a gas permeable but generally liquid impermeable barrier so that gas can flow from the lower side of the mat but liquid cannot flow into the mat unless it is sufficiently pressurized. For example, the lower side may be adapted to limit liquid with pressures less than 50 psi from flowing into the chamber.

Also in any of the above mats, the mat may include an intermediate layer formed from gas permeable material, such as an open-cell foam or spacer fabric, including a 3D fabric.

In a further aspect, the impermeable barrier may be formed by an impermeable material coated on or bonded to the upper side of the intermediate layer to thereby form a gas and liquid impermeable barrier at the upper side of the intermediate layer. Similarly, the lower layer may be formed on the lower side of the intermediate layer by a gas permeable, but generally liquid impermeable material, which may be coated on or bonded to the intermediate layer at the lower side thereof to thereby form a gas permeable, generally liquid impermeable barrier at the lower side. Alternately, the lower layer may be formed from a permeable material.

Further, in any of the above mats, the mat itself may be formed from a drop-stitch fabric, for example, a Sevytex® fabric, which forms the upper and lower sides of the mat and when deflated assumes a flat compact configuration but when inflated increases the separation between the upper and lower sides but only up to a separation where the mat has thickness less than 1″, optionally less than ½″, or a thickness of about ¼″.

In another form of the invention, a patient transfer device includes a mat with a liquid and gas permeable compressible intermediate layer having an upper side and a lower side, which is permeable both laterally and longitudinally through the layer and orthogonally to the layer. The upper layer or side of the mat is impermeable to gas and liquids, and the lower side or layer of the mat is gas permeable, but limits liquid with pressures less than 50 psi from flowing into the mat. The mat includes a chamber formed around the intermediate layer, which is operable to be in fluid communication with an air source such that when air flows into the chamber, the air will flow through the intermediate layer and further from the gas permeable lower side to form an air film between the mat and a surface on which the mat is supported at its lower side.

In one aspect, the upper layer is formed on the upper side of the intermediate layer. For example, an impermeable material may be coated on or bonded to the upper side of the intermediate layer to thereby form a gas and liquid impermeable barrier at the upper side of the intermediate layer. Similarly, the lower layer may be formed on the lower side of the intermediate layer by a gas permeable, but generally liquid impermeable material, which may be coated on or bonded to the intermediate layer at the lower side thereof to thereby form a gas permeable, generally liquid impermeable barrier at the lower side.

In any of the above forms of the invention, the mat may be provided with an inlet, for example, at the lower side, upper side, or at the edge of the mat, which is adapted to couple to an air source.

In accordance with yet another form of the invention, a patient transfer mat includes a liquid and gas permeable compressible intermediate layer having an upper side and a lower side, a liquid and gas impermeable barrier at the upper side of the intermediate layer for facing a patient, and a generally liquid impermeable, gas permeable barrier at the lower side for facing a support surface. The liquid and gas impermeable barrier and the generally liquid impermeable, gas permeable barrier enclose the intermediate layer to thereby form a chamber about the intermediate layer. Further, the barriers are bonded to or otherwise formed at the respective upper and lower sides of the intermediate layer. The mat further includes an inlet that is operable to be in fluid communication with the chamber and is adapted for connection to an air source such that when air flows into the mat, the air will flow into the chamber and through the intermediate layer and through the generally liquid impermeable, gas permeable barrier to form an air film between the mat and a surface on which the mat is supported at its lower side.

In any of the above, the liquid and gas impermeable barriers may be formed by a liquid and gas impermeable sheet. For example, the sheet may comprise a polymer sheet or a woven sheet with an impermeable coating, such a vinyl.

Similarly, the generally liquid impermeable, gas permeable barriers may be formed by a generally liquid impermeable, gas permeable sheet. For example, the liquid impermeable, gas permeable sheet may be formed from a non-woven sheet with a plurality of perforations that are sized to permit gas to flow through sheet but to limit the flow of a liquid therethrough. For example, the perforations may be provided in arrays across the liquid impermeable, gas permeable sheet such that they cover essentially the entire bottom surface of the mat.

Alternately, the generally liquid impermeable, gas permeable sheet may comprise a woven sheet with a weave that forms a plurality of interstices, with the interstices sized to permit gas to flow through the sheet but to prevent the flow of a liquid therethrough.

In yet a further aspect, the generally liquid impermeable, gas permeable sheet may comprise a woven sheet with a coating, which is perforated to form a plurality of perforations that are sized to permit gas to flow through the sheet but to prevent the flow of a liquid therethrough.

In addition, each of the sheets may be bonded to the respective side of the intermediate layer. For example, the sheets may be bonded to the intermediate layer by an adhesive bond, including a bond formed by an intermediate adhesive layer (such as a sprayed on or brushed on coating of adhesive, a film of adhesive, or a fabric impregnated with adhesive), or a chemical bond (based on their chemical composition), or heat bond (e.g. welds). Further, the sheets are bonded to the intermediate layer with a substantially continuous bond (generally only interrupted by the interstices in the material forming the intermediate layer) so that together they form a substantially monolithic body and consequently form a plurality of ties or tethers between the upper side and the lower side of the mat with the material forming the intermediate layer. In this manner, the mat will not tend to billow, taco or hot dog—and instead, will retain its generally flat shape and the range of variability in the top and bottom topography is minimal.

In further aspects, the generally liquid impermeable, gas permeable sheets may include a plurality of perforations, which are sized to permit gas to flow through the generally liquid impermeable, gas permeable sheets but to limit the flow of a liquid therethrough. For example, the perforations may be sized to limit liquids from passing through that have a pressure of under 50 psi. For example, the perforations may be provided in arrays across the liquid impermeable, gas permeable sheets such they cover essentially the entire bottom surface of the mats. Consequently, when a portion of the mat aligned over a gap or discontinuity there will still be sufficient air film under the remainder of the mat to facilitate the transfer.

In another aspect, the barriers are formed by a coating, such as a sprayed on coating. In the case of the generally liquid impermeable, gas permeable barrier, an impermeable coating may be applied and then perforations are formed, which are sized to permit gas to flow through sheet but to limit the flow of a liquid therethrough if the liquid has a pressure of under 50 psi.

According to yet other aspects, the intermediate layers of any of the above mats may comprise an open cell foam, such as an open cell polyurethane foam. Alternately, or in addition the intermediate layers may comprise a three-dimensional (3D) knit fabric. In addition, the intermediate layers may be formed from a drop-stitch fabric, such as a Sevytex® fabric. Optionally, the intermediate layers have uniform thicknesses; though the intermediate layers may have varying thicknesses. For example, the thickness at the edges of the intermediate layer may be thicker to form a cradle for the patient.

In yet other aspects, the mats may incorporate structures to facilitate handling, such as straps, handholds or the like. For example, straps may be mounted to the top or bottom sides of the mats or may be secured to the mats between the sheets forming the barriers.

Alternately, the mats may incorporate one or more flanges that extend from a lateral side or sides of the mats. The flange or flanges then may provide a mounting surface for a strap or straps or handholds. Alternately, the flanges may be configured to form the straps or handholds. The flanges may be flexible and further may be formed from one or both of the sheets forming the barriers. In addition, the flanges may be inflatable to form pontoons, which may be used to cradle a patient.

Alternately, the flanges may be formed from flexible sheets or panels that are secured to one or both of the sheets. For example, when using non-structural barriers, such as when the barriers are formed from coatings rather than sheets, then the flange may be coupled the intermediate layer.

The flanges may extend the full length of the lateral side of the mat or may extend only along a portion of the length of the mat. Further, multiple flanges may be provide at one or more sides. For example, flanges may be provided at the head end of the lateral side of the mat and at the foot end of lateral side of the mat. Further, flanges may be provided at the foot end or head end of the mat or both to facilitate handling of the mat and the patient supported thereon. Further, the flanges may be tucked under a mattress to secure the mat to the mattress.

In addition, the flanges may be formed as semi-flexible flanges to form guide surfaces for the mat. For example, when sliding the mat between two surfaces where the surface from which the mat is being transferred is lower, the flanges may be used to guide and lift the edge of the mat upwardly as it makes contact with the adjacent surface.

Accordingly, the present invention provides a patient transfer mat may be more compact than conventional patient air pallets, and further require less air flow to remain operational. Further, the mat can be configured to provide enhanced infection control. In addition, the mat may generate an air film which facilitates the transfer of a patient but which is not lost or compromised when a portion of the mat is aligned over a gap or discontinuity.

In accordance with still other aspects of the invention, a system and method for automatically controlling the air flow to the mat is provided. The system and method include a blower or air pump that inflates the inflatable mat and which is controlled by a controller that automatically adjusts the speed of the blower to compensate for air losses in the air mat. The automatic adjustment of the blower enables the motor of the blower to operate at reduced power levels when little air flow is needed and to automatically increase its power levels when conditions warrant. This helps reduce wear and tear on the blower, reduces the noise level of the blower, conserves energy, and helps to lower the temperature of the air inside the inflatable mat, which may otherwise reach uncomfortable levels for the patient being transferred.

In one aspect, a patient lateral transfer system is provided that includes an inflatable mat, a blower with a motor, a hose, at least one sensor, and a motor controller. The inflatable mat includes a top surface and a bottom surface wherein the top surface supports a patient and the bottom surface includes a plurality of perforations that allow air to escape in a manner that creates an air bearing underneath the inflatable mat. The hose connects to the blower and the inflatable mat such that the blower can deliver pressurized air to the inflatable mat when the hose is connected therebetween. The sensor detects at least one of air pressure in the inflatable mat and a flow rate of air being blown from the blower to the inflatable mat, and the sensor outputs a signal relating to at least one of the air pressure and flow rate. The motor controller controls the motor based at least partially upon the signal from the sensor.

According to another aspect, a method for controlling a motor of a blower that is adapted to inflate an inflatable mat is provided. The mat includes a top surface and a bottom surface wherein the bottom surface includes a plurality of perforations adapted to generate an air cushion when the inflatable mat is inflated. The method includes operating a motor within the blower at a first speed during an initial inflation of the inflatable mat; decreasing a speed of the motor subsequent to the inflation of the inflatable mat; and increasing a speed of the motor in order to compensate for air loss from the inflatable mat as the mat is moved from a first surface to a second, spaced apart surface.

According to yet another aspect, a method for laterally transferring a patient from a first support surface to a second support surface is provided. The method includes positioning a patient on an inflatable mat on the first support surface wherein the top surface of the mat supports the patient and the bottom surface of the mat includes a plurality of perforations that allow pressurized air contained within the inflatable mat to escape. The method further includes inflating the inflatable mat with a blower having a motor; moving the inflatable mat from the first surface to the second surface; and, during movement of the inflatable mat from the first surface to the second surface, automatically increasing a speed of the blower motor when the amount of air that escapes from the inflatable mat increases and automatically decreasing the speed of the blower motor when the amount of air escaping from the mat decreases.

According to other aspects, the motor controller may be configured to adjust a characteristic of the motor automatically after the inflatable mat is fully inflated, such as, but not limited to, a flow rate, a speed, or a pressure generated by the motor within the mat. The motor controller may also be configured to automatically determine when the mat is fully inflated by monitoring an output of the flow rate sensor. The motor controller may also vary a speed or power of the motor in response to pressure changes wherein the varying includes increasing the speed or power of the motor when substantial losses of air from the inflatable mat occur during lateral transport of the mat, and decreasing the speed or power of the motor when substantially no losses of air from the mat occur. The motor controller may further be adapted to control the motor based at least partially upon the output from a timer. The methods for controlling the blower motor may also include making adjustments to the speed of the motor based upon either or both of the air pressure and the flow rate. Still further, the methods for controlling the blower motor may further be based at least partially upon the output from a timer.

These and other objects, advantages, purposes, and features of the invention will become more apparent from the study of the following description taken in conjunction with the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIG. 1, the numeral10generally designate a patient transfer device of the present invention. As will be more fully described below, the patient transfer device comprises an air mat12that generates an air film and, optionally, across a significant portion, if not substantially it's entire portion, of its lower surface for transferring a patient across a surface and between surfaces. Although the term “patient” is used herein, it should be understood that patient should be broadly construed to not only include people awaiting or under medical care, but also to include invalids or other people in need of assistance. Further, the mat may be operated with a lower air flow than conventional air bearing pallets while still achieving the same or better ease of transfer than prior art air bearing pallets. Because lower air flow is needed, device10may be operated with a smaller blower than used heretofore with the prior art air bearing pallets or with a pump, which saves energy, reduces noise, and generates less heat.

Referring toFIGS. 2 and 3, mat12includes an upper side14for supporting a patient thereon and a lower side16, which is supported on a support surface S such as a bed, stretcher, or the like. Further, mat12includes an air chamber18, which when filled with air generates an air film at lower side16. As will be more fully described below, upper surface14comprises an impermeable barrier, while lower side16comprises a gas permeable barrier through which air flows to form the air film when chamber18is inflated. Optionally, as will be more fully described below, lower side16may also comprise a generally liquid impermeable, gas permeable barrier to allow air to flow from lower side16prevent, at least over certain ranges of pressures, liquids from flowing into the mat.

Chamber18may be filled with a flexible, liquid and gas permeable layer20that is intermediate upper and lower sides14and16and which is permeable in all directions. In this manner, when air flows into layer20, the air can move longitudinally, laterally or transversely through layer20. To inflate chamber18, mat12includes an inlet22, which may be located at the upper side14, lower side16, or at the edge or lateral side of the mat. Inlet22is adapted, for example by way of a conduit24, to couple to an air supply source, such as a blower. When air flows into conduit24and mat12through inlet22, the air will flow through the intermediate layer20and then exit through the gas permeable lower side16to thereby form an air film beneath mat12.

Referring toFIG. 3, the gas and liquid impermeable side14may be formed from a sheet24, which is bonded to an upper side20aof intermediate layer by adhesive28. Similarly, generally gas permeable side16may also be formed from a gas permeable sheet26, which is bonded to lower side20bof intermediate layer20by adhesive28, such as a urethane based adhesive. For example, adhesive28may be coated, sprayed or otherwise applied to the respective upper and lower sides of the intermediate layer; or adhesive28may be provided in the form of a film or a sheet that is embedded with an adhesive, which is then activated for example by heat or other energy sources. Alternately, the sheet may be bonded by a chemical interaction with the intermediate layer.

In this manner the upper and lower sides of the mat are interconnected by a substantially continuous connection so that the upper and lower sides together with the intermediate layer form a monolithic body so that when mat12is inflated, the upper and lower sides will retain their spacing and orientation so that they remain substantially uniformly spaced. In other words—when inflated the upper side does not raise relative to the lower side in an appreciable amount and will raise less than 3″, less than 2″, less than 1″, less than ½″, or optionally less than ¼ relative to the lower surface and, hence, relative to the surface supporting the mat. As a result, the patient is not raised a significant amount either, thus providing increased stability to the patient. Further, the range of variability in the top and bottom topography of the mat when the mat is inflated will be minimal. For example, the variation in height between the upper and lower sides will be less than ¼″, optionally less than ⅛″, and may be less than 1/16″ variation. For example, in the case of an intermediate layer with uniform thickness, the upper and lower sides will remain substantially parallel, and each side will remain substantially flat.

Liquid and gas impermeable sheet22may be formed from an impermeable material, such as a nylon or a plastic, or may be formed from a permeable material, such as a woven sheet of material, which then includes a liquid and gas impermeable coating on one of its surfaces to thereby form an impermeable sheet. Similarly, sheet26may be formed from an impermeable sheet but which is then made gas permeable by forming small perforations in the sheet. For example, the size of the perforations may be on the order of thousands of an inch to thereby form a gas permeable, but substantial liquid impermeable sheet. Further, the density of the perforations may fall, for example in a range of 50 to 100 holes per square inch. The size of the openings may range, for example, from about 1/20,000 inch in diameter to about 1/5,000 of inch in diameter for example. In addition, it has been found that for openings having a diameter on the order of about 1/20,000 inch, the number of openings to achieve the desired film is about 1500-2500 and optionally about 2000 for an adult size mat, for example on the order of a 36″ by 84″ mat. It has been found that for openings having a diameter on the order of about 1/8,000 inch the number of openings to achieve the desired film is about 8,000 to 12,000 and optionally about 10,000 for an adult size mat. Similarly, it has been found that for openings having a diameter on the order of about 1/5,000 inch the number of openings to achieve the desired film is about 30,000 to 34,000 and optionally about 32,000. Thus, depending on the size of the openings, an adult size mat may have any where from 1,500 to 34,000 openings or perforations on its lower side. It also has been found that better performance is achieved when openings or perforations (or interstices) are provided across the full length and width of the lower side of the mat.

Alternately, sheet26may be formed from a woven material, which has interstices that are sized so that the weave is gas permeable and further optionally generally liquid impermeable, for example for liquids below 50 psi. For example, suitable generally liquid impermeable, gas permeable materials may include Tyvek or Gortex. Other suitable woven fabrics generally include fabrics formed from polyolefins, urethanes, polypropylenes, and polyethers. Although described in reference to the perforations or interstices covering the full extent of the downwardly facing side of the mat, it should be understood that the mat may be formed with perforations or interstices over only a portion or over portions of the lower side of the mat.

Regardless of the bonding method, to achieve optimal performance, the sheets are bonded to the intermediate layer with a substantially continuous bond so that they form a substantially monolithic body with the intermediate body. Further, they are sealed together about intermediate layer20at a perimeter joint or seam15, to thereby full enclose intermediate layer20and thereby form the chamber about layer20. In this manner, the intermediate layer forms a continuous connection—that is a plurality of closely spaced ties or tethers between the upper side and lower side of the mat, or what is referred to herein a “continuous baffle”. With this construction, mat12does not exhibit any significant billowing effects, nor does it exhibit any tacking effects. Instead, as noted above with a uniform thickness intermediate layer, the upper and lower sides of the mat remain substantially uniformly spaced and remain generally planar with its lower side16lying substantially flat against surface S on which it is supported. In this manner, the air flowing through lower surface16can form an air film across substantially the entire side16facing support surface S. When combined with the relatively air flow, mat12will not experience a significant loss of the air film when the mat is transferred from surface S across a gap to an adjacent surface; hence, mat12provides an ease of transfer that is at least as equal to or better than most prior art air bearing pallet designs.

In other forms, the gas and liquid impermeable side14may be formed by a liquid and gas impermeable coating applied to the upper side20aof intermediate layer20. For example, suitable coatings may include urethane coatings. Similarly, the gas permeable, and optionally, generally liquid impermeable side may be formed by a coating applied to lower side20bof intermediate layer20, which is then perforated. The coatings are then joined at perimeter joint or seam15, again to thereby form chamber18about layer20.

As noted above, to form the generally liquid impermeable barrier the size of the perforations or the openings formed by the interstices formed in the woven fabric are such that liquids will not flow into the mat but will allow gas to flow from the mat, which provides enhanced contamination control. In addition, with the smaller openings, the flow of air from side16, while sufficient to form an air film, is sufficiently low to reduce the required pressure and gas flow into mat12. For example, it has been found that the mat12may operate using a 200 watt electric blower as compared to a 1200 watt electric blower currently used on patient air pallet designs.

As noted above, intermediate layer20comprises a liquid and gas permeable material. For example, suitable materials include open cell foams, including an open cell urethane or polyurethane foam. Further, a suitable foam has a relatively low density but a high porosity, for example 30 ppi. As noted above, by bonding the upper and lower sheets to the upper and lower surfaces of the intermediate layer or forming the barriers at the upper and lower surfaces of the intermediate layer, namely the foam, the foam will form a substantially continuous connection (e.g. form thousands of ties or tethers spaced at less than 1/16″ apart, optionally less than 1/32″ apart, and more typically less than 1/64″ apart) between the upper and lower side of the mat. Depending on the foam density (or 3D knit fabric noted below), there could be tens of thousands of tethers. However, unlike the prior art air bearing pallet with discrete spaced apart baffles or tethers, the foam will allow lateral and longitudinal flow of air through the intermediate layer, in addition to the transverse flow through the thickness of the intermediate layer. As noted, therefore, the intermediate layer forms a “continuous baffle” between the upper and lower sides of the mat.

Alternately, intermediate layer20may comprise a three-dimensional fabric. An example of a suitable three-dimensional fabric is available from Dartex. In a similar manner to the foam, a 3-D material emulates the continuous baffle provided in the previous embodiment.

In another form, the intermediate layer or the mat12may be formed form a drop-stitch fabric, for example, a drop-stitch fabric available under the trademark Sevytex®. The drop-stitch fabric has an upper surface and a lower surface which are interconnected by strands or fibers. The upper and lower sides are woven so that the fabric is liquid and gas impermeable. When un-inflated, the strands provide no compression resistance; therefore the mat is relatively flat. When air is flowed into the space between the upper and lower sides, the strands become aligned and oriented generally perpendicular to the upper and lower sides and provide compression resistance and space the upper and lower sides apart. The lower side then is provided with suitable perforations to achieve the desired gas permeability while retaining the liquid impermeability as noted above. Alternately, the drop-stitch fabric may be coated or provided with sheets (adhered to or otherwise laminated to the drop-stitch fabric) as described above.

In any of the above embodiment, the thickness of the mat may be significantly reduced over the prior art air bearing pallets, which typically range from 6 to 10 inches in height when inflated. For example, the thickness of the mat may reduced to a range of 3″ to ½″ or down to ⅛″, depending on the capacity desired for the mat. It has been found that a 2″ thick intermediate layer of an open cell polyurethane will adequately transfer a patient of 600 pounds or less. It has also been found that a ¼″ thick mat formed from a 3D fabric intermediate layer will adequately transfer a patient of at least 200 pounds.

An exemplary size that can be used for mat12is a 36″ by 84″ mat. For mats of this size with a thickness of 3″, this means the volume of the chamber formed by the intermediate layer may be approximately 6 cubic feet. A mat of this size with a thickness of about 2″ may have a chamber volume of about 4 cubic feet. Similarly, mats of this size with a thickness of about 1″ can have a chamber volume of about 2 cubic feet. It has been found that a 36″ by 84″ mat with a thickness of about ½″ or about ¼″ can be operational for transferring a patient with an air flow of about 7-10 cubic feet per minute. With a less than 1 cubic foot volume (e.g. a ½″ thick mat may have a chamber volume of about 0.98 cubic feet), optionally less than about a 0.5 cubic foot volume (e.g. ¼″ mats would have a chamber volume of approximately 0.49 cubic feet) or about a 0.3 cubic foot volume (e.g. for a ⅛″ thick mat), the pressure in the mat with the noted 7-10 cubic feet per minute air flow, and with the gas permeabilities noted above, ranges from about 3 to 4 psi. It should be understood that while several specific examples of the mat thickness have been provided, the thickness may fall between these valves and, further, may exceed these values, though one or more of the attendant benefits of the thinner mats described herein, e.g. stability, reduced volume, etc. may be reduced.

Given the reduction in the volume of the chamber over prior art air transfer mats (which typically run on the order of 18 cubic feet), the outside diameter of the inlet22may be reduced over prior art air bearing pallet inlets. For example, it has been found that sufficient air flow can be achieved using, as noted above, a 200 watt blower and, further, with a % inch inlet or tubing at the inlet. Further, in lieu of a blower, a small pump or compressor may be used. For example, a small pump may be used, for example an 80 watt pump.

Consequently, in addition to the reducing size of the mat, which makes stowing much easier than in prior art air bearing pallets, the reduced size of the chamber allows a pump to be used and also a pump that is small enough to be integrated into the surface should a fully contained device be desired. For example, an internal or external pocket may be provided to house such a pump. In addition, the noise and heat generated by the reduced sized blower or the pump is significantly reduced than prior art air pallet blowers. Given the significantly reduced volume of the chamber, the fill time may also be drastically reduced, and the distance a patient is lifted from the surface on which the mat is supported may be also drastically reduced from a conventional air bearing pallet, which lifts a patient in a range of 6-10 inches off the supporting surface, to less than 3″, less than 2″, less than 1″, or optionally less than ½″ and as low as about ⅛″ off the surface, which increases the stability of the patient.

Referring again toFIG. 1, mat12may include one or more flanges30and32. Flanges30and32may be provided at the opposed lateral sides of mat12and may be used as a mounting surface for straps34or hand holds, which also may be formed from strap material. The flanges may be formed from the sheets forming the upper and lower layers or may be formed from separate sheets or panels that are attached to the mat. For example, when formed from separate panels or sheets, flanges30and32may be secured at the joint or seam15formed between the upper and lower sheets and, further, may be joined to the intermediate layer, for example by an adhesive, fasteners, or by chemical bonding. Further, flanges30may be flexible flanges or may be rigid flanges.

Referring toFIG. 6, where the flanges are formed from the sheets that form the upper and lower sides of the mat, a reinforcement member36may be inserted between the extensions or flaps22aand26aof the upper and lower sheets which form the upper and lower sides of mat12. Extensions22aand26aform the upper and lower sheets of30a,30bof the flanges30,32and may be joined together with a bond, such as an adhesive bond, a chemical bond, or heat-activated bond, with the reinforcement member captured between the joined extensions or flaps.

As noted above, flanges30and32may provide a mounting surface for straps34. Referring toFIG. 4, straps34may be surface mounted to the flanges30,32or may be sandwiched between the respective upper and lower sheets30a,30bof the flanges30,32.

Referring toFIGS. 7 and 8, whether flanges30or32are flexible or at least partially semi-rigid, flanges30and32may be used to form a guide surface for mat12when, for example mat12is transferring from a surface S, which is lower than the adjacent surface S1. As best seen inFIG. 7, when a user pulls on the strap34, which is secured to a respective flange, the respective flange will tend to lift up and, further, pull on the edge of the mat12to thereby lift mat12over the edge of the adjacent higher surface.

It should be understood that the size and length of the flanges may be varied. For example, the flanges may be sized so that when the mat is positioned on top of a mattress or other supporting surface, the flanges can be extended under or tucked under the mattress so as to releasably secure the mat to the mattress. Furthermore, multiple flanges may be provided on each side, and also may be provided at the foot and head end of the mat. For example, one flange may be provided at the head end of the lateral side of the mat and another flange may be provided at the foot end of the lateral side of the mat. It should be understood that the shape and thickness of the flange may be varied as desired. Furthermore, the respective flanges may have formed therein transverse openings to form hand holds.

Also, the flanges may be inflated so that when inflated they may form pontoons for the mat; therefore, each flange may include its own inlet. Alternately or in addition, each flange may have a chamber that is in fluid communication with chamber18so that when chamber18is inflated so too are the flanges.

In the illustrated embodiment, intermediate layer20has a generally uniform thickness across its width and length. However, it should be understood that the intermediate layer20may have a varying cross-section. For example, the thickness of the lateral portions may be increased in one or more regions to create a cradling effect for the patient that is supported thereon. For example, the lateral side edges of the intermediate layer may include wedge-shaped cross-sections or arcuate-shaped cross-sections. Further, the intermediate layer20may have indentations in the intermediate or central portion12aof mat12to provide localized depressed areas for the legs, the torso, or just the head. This may provide the patient with an increased feeling of security. Furthermore, this cradling effect may be achieved just through the material properties of the foam or 3-D fabric.

Control System for Air Transfer Device

FIGS. 9-13illustrate various aspects of a method and system for controlling a patient lateral transfer system120. The patient lateral transfer system120may utilize the mat12and transfer device10, described above, or it may utilize mats of entirely different construction, such as described below and illustrated inFIGS. 9-13.

The patient lateral transfer system120according to one embodiment is depicted inFIG. 9. Patient lateral transfer system120is designed to facilitate movement of a patient122from a first patient support device124ato a second patient support device124b. In the embodiment illustrated inFIG. 9, the first patient support device124ais a bed and the second patient support device124bis a stretcher. It will be understood by those skilled in the art, however, that patient lateral transfer system120may be utilized with other types of patient support devices124, including, but not limited to, cots, surgical tables, gurneys, chairs, and other patient support devices.

Patient lateral transfer system120includes an inflatable mat126, a blower128, and a hose130(FIG. 9). As was noted above, system120may be used with mat12or with mat126, or with still other types of mats. Inflatable mat126includes a top surface132that is adapted to support patient122thereon. When it is time to transfer the patient from one patient support device124to another, inflatable mat126is inflated by way of blower128. Inflatable mat126is then slid from the first patient support device124ato the adjacent patient support device124b. Thereafter, mat126may be deflated and removed from underneath the patient, either immediately after transfer, or after the passage of any suitable amount of time. Alternatively, mat126may be left deflated underneath the patient until it is desirable to transfer the patient to another surface.

An illustrative manner of constructing mat126is depicted in greater detail inFIG. 10. As noted above, mat126includes a top surface132that is adapted to support the patient. As shown inFIG. 10, top surface132may be contoured to provide better comfort for the patient, although the type of contouring may vary widely. In other embodiments, top surface132may not provide any contouring at all. In the embodiment illustrated inFIG. 10, top surface132includes a raised perimeter134that extends around the edges of top surface132.

In addition to top surface132, inflatable mat126includes a pair of sides136, a foot end138, a head end140, and a bottom surface142. Inflatable mat126may further include, in some embodiments, one or more straps144for helping secure patient122to mat126, as well as one or more hand holds146for allowing personnel to more easily grasp and manipulate mat126. Mat126further includes an inlet port148adapted to couple to an end of hose130of blower128for receiving air.

A cross sectional diagram of an illustrative mat126taken along a path from one side136of mat126to another side136is illustrated inFIG. 11. The mat126illustrated inFIG. 11is a simplified diagram representing the basic construction principles of mat126. The particular shapes, sizes, and layout of the features of the mat126illustrated inFIG. 11may vary from that shown, as will be discussed more below. As but one example, the mat126ofFIG. 11includes a generally flat top surface132that, as noted earlier, may be varied to include suitable contouring for providing better comfort to the patient and/or to provide a surface that a patient is more likely to stick to during transfer to another patient support device124(i.e. a surface on which a patient is less likely to slide upon during transfer).

Bottom surface142of mat126includes a plurality of perforations150. Perforations150are configured to allow a sufficient amount of air to escape from within mat126such that an air bearing152(FIG. 12) may be formed between bottom surface142and a top surface154of patient support device124. In the embodiment illustrated inFIG. 12, both bottom surface142and top surface132of mat126include a plurality of indentations156. Such indentations may be the result of baffles (not shown) defined in the interior of mat126, or may be defined in other manners. The precise shape of the indentations shown inFIGS. 11 and 12is not intended to be of significance, and these shapes may vary substantially.

In the bottom surface142, the perforations150are defined adjacent the indentations156. The size, shape, depth, surface tension/stiffness, airflow through, quantity, and location of both perforations150and indentations156can be varied from that illustrated inFIG. 11. The design and layout of perforations150and indentations156may affect the lifting performance and efficiency of mat126and can be implemented in a wide variety of different manners that provide satisfactory results. Several examples of the different configurations for mat126and its bottom surface142are disclosed in commonly assigned, copending U.S. application Ser. No. 11/801,007 filed May 8, 2007 by Thomas DeLuca et al, and entitled “AIR BEARING PALLET,” the complete disclosure of which is hereby incorporated herein by reference. Other suitable mats that may be used with patient transfer system120are those manufactured by Stryker Corporation of Kalamazoo, Mich., the assignee of this application, under the model numbers 3061-500-028, 3061-500-032, and 3061-500-046, which are marketed under the Stryker Glide™ trademark.

When air is pumped into inflatable mat126from blower128via hose130, a relatively small amount of air “leaks” through perforations150and generally fills in the spaces defined between indentations156and the top surface154of the patient support device124upon which the patient is supported. As the air pressure inside of mat126builds, the air pressure within these spaces also builds until the pressurized air eventually lifts the mat126upon air bearing152in a manner similar to conventional hovercrafts. As long as pressurized air continues to be supplied to mat126via blower128, air bearing152will continue to lift mat126slightly off of the top surface154of patient support device124. This lifting reduces the frictional forces between bottom surface142of mat126and top surface154of patient support device124, thereby allowing mat126to slide laterally with respect to top surface154with little resistance. This reduced resistance enables health care personnel to more easily push and/or pull mat126from one patient support device124to another, thereby requiring less effort on the part of the health care personnel. Indeed, the use of mat126and the air bearing152upon which it rides may reduce the frictional resistance of sliding mat126to such an extent that the efforts of one or more health care personnel that would otherwise be necessary for patient transfer are no longer needed.

In the past, the use of inflatable mats126has involved a blower that runs continuously at a generally constant high speed during the initial inflation of mat126and the subsequent transfer of the patient from one surface154to another. This substantially continuous operation of the motor often results in the motor doing more work than is necessary for the patient transfer, thereby creating the unwanted side effects of excessive noise and unnecessary energy usage. In addition, the heat from the blower motor operating at a continuously high speed can heat the air inside of mat126to a level that is uncomfortable for the patient.

Patient transfer system120overcomes these difficulties by including a motor controller158(FIG. 13) that automatically controls the speed of a blower motor164in a manner that is more efficient, produces less noise, and which heats the pressurized air to a lesser degree than prior patient transfer systems. The motor controller158utilizes feedback from one or more sensors160that detect one or more quantities relating to inflatable mat126. For example, in one embodiment, sensor160is an air flow sensor that detects the amount of air flowing into inflatable mat126from blower128. In another embodiment, sensor160is an air pressure sensor that detects the air pressure inside of inflatable mat126, or inside of hose130at a position that is in fluid communication with the inside of inflatable mat126. In still other embodiments, both an air flow sensor160and an air pressure sensor160may be utilized together. In still other embodiments, a timer162may be utilized for carrying out the control of motor164of blower128. In still other embodiments, additional sensors for sensing information useful to the control of blower128may also be utilized, in any suitable combination with one or more of the above-mentioned sensors160.

As noted above, patient transfer system120includes blower128, hose130, and mat126. In the embodiment illustrated inFIG. 13, blower128includes motor controller158that controls the speed and/or other characteristics of motor164, such as, but not limited to, torque, the voltage supplied to motor164, the current supplied to motor164, and/or any combination of these characteristics. Motor164is positioned within an air channel or conduit174internal to blower128and includes the appropriate fan blades or other structures necessary to propel air from an inlet port168toward an outlet port172when the motor164runs. Outlet port172is adapted to be releasably coupled to hose130, which, in the embodiment illustrated inFIG. 13, includes one or more sensors160positioned therein. It will be understood by those skilled in the art, of course, that the position of sensors160could be changed from that shown inFIG. 13, such as, but not limited to, positioning one or more of sensors160between, or adjacent to, the connection of outlet port172to hose130, or positioning one or more of sensors160within blower128in a location in fluid communication with the portion of air channel174downstream of motor164. Other locations are also possible. Motor164may be any suitable type of motor, whether DC, AC, frequency controlled, brushed or brushless, or other type of motor.

In general, motor controller158of patient transfer system120controls the motor164of blower128such that sufficient air pressure is maintained inside of mat126to keep it aloft via air bearing152, but without creating excessive air pressure and excessive speeds of the motor164. Stated alternatively, motor controller158controls motor164in such a way as to automatically adjust to the changing air needs of inflatable mat126during the patient transfer. The air needs of inflatable mat126dynamically change during the process of patient transfer for several reasons. For example, it is typically desirable to inflate mat126in a relatively short period of time, thereby reducing the time that the patient and health care personnel have to wait to begin the patient transfer process. As a result, it is often desirable to operate blower128at a relatively high speed so that mat126will be inflated relatively quickly. However, after mat126is inflated and is lifted onto air bearing152, the consumption of air by inflatable mat126will typically drop as it no longer needs air for inflation, but rather only needs air for maintaining air bearing152, which is typically less.

During movement of mat126in a lateral direction166(FIG. 12), the air needs of mat126may also change. These changes generally arise due to one or more of perforations150being shifted to a position in which fluid communication between the internal air inside mat126and the ambient air outside of mat126becomes more pronounced. In other words, the movement of mat126may result in one or more of the perforations150becoming substantially exposed to ambient air, thereby allowing a greater amount of air to escape through the perforations150than would otherwise happen if the perforation were merely supplying only the air necessary to maintain the air bearing152. One example of such a situation is depicted inFIG. 12.

FIG. 12is a side schematic view of an air mat126that is approximately midway through the process of being transferred from a first top surface154of a first patient support device124ato a second top surface154of a second patient support device124b. As can be seen therein, at least one indentation156aand its corresponding perforation150aare generally completely exposed to the surrounding, ambient air pressure. Stated alternatively, there is no air cushion supplied immediately adjacent perforation150aand indentation156a. This is because of a lateral gap170that exists between the two top surfaces154of the adjacent patient handling devices124. The lateral gap170means that there is no surface immediately underneath perforation150aand indentation156athat would otherwise partially shield these two structures from the outside, ambient air. As a result, any perforations150that travel over lateral gap170, such as perforation150ainFIG. 12, will be exposed, at least temporarily, to the ambient air pressure within the room, which, due to blower128, is substantially less than the air pressure inside of mat126. As a result, the air inside of mat126will escape at a higher rate through the perforations150when they are positioned above lateral gap170than when they are positioned directly on top of one of surfaces154. The passage of mat126over lateral gap170therefore results in a greater consumption of air by mat126, at least to the extent it is desirable to maintain the same level of inflation in mat126.

It is also possible for the air bearing152adjacent one or more particular indentations156to be disrupted by other causes besides the presence of lateral gap170. One such cause may be the weight distribution of the patient, or a change in the weight distribution of the patient on mat126. The particular weight distribution of the patient may cause portions of mat126to bend and/or twist in such a manner as to essentially expose one or more perforations150to ambient air pressure, thereby allowing a greater amount of air to escape than would otherwise. Such increased rates of air leakage result in greater air needs of inflatable mat126. Still other causes may also lead to increased air needs for mat126, such as roughness and/or discontinuities in one or both of top surfaces154.

Patient lateral transfer system120is adapted to control blower128such that it increases its speed when more air is needed by mat126and decreases its speed when less air is required by mat126. Motor controller158determines the air needs of mat126through one or more sensors160, either alone or in combination with a timer162. In one embodiment, motor controller158operates motor164at a relatively high rate of speed during the initial inflation of mat126. After controller158determines that the mat126is completely inflated (in any of a variety of different manners that will be discussed below), controller158reduces the speed of mat126to a level sufficient to maintain the air cushion or air bearing152. Thereafter, motor controller158monitors the air needs of mat126and increases the speed of motor164as necessary and decreases the speed of motor164when appropriate.

In one embodiment, patient lateral transfer system120utilizes only a single sensor160that detects air flow. In that embodiment, motor controller158initially operates motor164at a high rate of speed until mat126is inflated. Motor controller158detects that mat126is fully inflated when the air flow detected by sensor160drops. This drop is due to the initially large amounts of air flow that occur when mat126is being inflated followed by the smaller amount of air that, once the mat is inflated, escapes through perforations150to maintain the air bearing152. In this embodiment, after motor controller158detects the drop in air flow and implements a corresponding drop in the speed of motor164, motor controller158continues to monitor the output signals from sensor160. When sensor160thereafter detects an increase in air flow, it is presumed that such an increase in air flow is due to increased air flowing out of inflatable mat126, and that mat126therefore needs more air in order to maintain is current state of inflation, as well as its current air bearing152. Motor controller158therefore sends the appropriate commands to motor164that cause the speed of motor164to increase, thereby supplying more air to mat126. When motor controller158detects, via sensor160, that the air flow rate has once again decreased back to the relatively low level associated with all of perforations150creating air bearings152, motor controller158will reduce the speed of motor164. In such an embodiment, motor controller158may therefore operate motor164at two distinct speeds: a relatively high speed and a relatively low speed, depending upon the sensed air flow. In other embodiments, motor controller158may be configured to operate motor164at more than two distinct speeds, such as, but not limited to, a low speed, a medium speed, and a high speed. Discrete speed levels beyond three are also possible. Indeed, in one embodiment, motor controller158may be implemented to operate motor164at generally continuously varying speeds, rather than a set of discrete speeds. In such embodiments, motor controller158may operate in such a manner that the speed of motor164tracks the air flow—that is, as the air flow into mat126increases, the speed of motor164is increased, and as the air flow into mat126decreases, the speed of motor164is decreased. The amount of the speed increase or decrease may be proportional to the change in air flow detected, or it may take on other relationships.

In other embodiments, patient lateral transfer system120may be implemented such that sensor160detects air pressure and system120utilizes no other feedback sensors other than air pressure sensor160. In such embodiments, motor controller158may operate in a manner generally similar to those described above with respect to an air flow sensor. That is, motor controller158may initially drive motor164at a relatively high rate in order to inflate mat126and thereafter relax the speed of motor164(at least for a small amount of time) until a lower, threshold level of pressure is reached. Thereafter, motor controller158may control the speed of the motor164based upon the output of the air pressure sensor160, with decreases in air pressure causing motor controller158to increase the speed of motor164and increases in air pressure causing motor controller158to decrease the speed of motor164. Such increases and decreases in the speed of motor164may be carried out by switching the speed of motor164to one of a plurality of different discrete speeds, or they may be carried out by varying the speed of motor164in a generally continuous fashion. Motor controller158may automatically determine that inflatable mat126is fully inflated in any suitable manner, such as, but not limited to, detecting the passage of a preset amount of time, monitoring the air pressure inside the mat until a specific condition regarding the rate at which the air pressure inside mat126changes is met, monitoring the air pressure inside the mat until a specific air pressure value is attained, or any other suitable methods.

In still other embodiments, a timer162may feed a time signal into motor controller158that is used in conjunction with either an air pressure sensor160or an air flow sensor160, or both. Motor controller158may carry out some or all of the control of motor164based either wholly or partially upon the outputs received from the timer162, and the degree to which timer162influences the control of motor164may vary as well. As an example, one embodiment of patient transfer system120utilizes a timer162for determining when inflatable mat126has initially been inflated. That is, motor controller158operates motor164at a relatively high speed during the initial inflation of mat126for a predetermined amount of time. Thereafter, motor controller158may switch to utilizing only the output of sensor160(whether air pressure or air flow) in controlling motor164. Alternatively, motor controller158may continue to utilize timer162in its control algorithms. Regardless of how motor164is used or not used after the inflation of mat126, the predetermined time period may be set to a known amount of time that it takes for mat126to be inflated at the selected speed of motor164, or it may be set to a slightly larger amount of time to accommodate for variations in inflation time that may occur due to temperature changes, mat size, patient weight, etc.

In still other embodiments, patient transfer system120may utilize two or more inputs into motor controller158that provide information that motor controller158uses in carrying out the control of motor164. The two or more inputs may comprise two different sensors160, such an air pressure sensor and an air flow sensor, or it may comprise multiple of the same types of sensors, such as two air flow sensors (which may be positioned physically at different locations). In still other alternatives, one of the multiple inputs into motor controller158may be timer162, as well as one or more other sensors besides air pressure and air flow sensors. Such additional sensors might include temperature sensors, humidity sensors, or still other types of sensors.

In any of the various embodiments discussed herein, motor controller158may be configured to utilize closed-loop feedback principles that involve proportional control, proportional-integral-derivative (MD) control, or any combination or permutation of proportional, integral, and derivative factors. Additionally, the selected feedback control algorithm may be cascaded with additional algorithms. Still further, non-linear feedback control formats may also be used, either alone or in combination with linear systems. The control data that is fed back into motor controller158may take on any of the various forms described herein; that is, it may comprise air pressure data, air flow data, time, temperature, humidity, or any other data useful for controlling the speed of motor164. The set point used in the feedback loop may correspond to any suitable parameter, such as air pressure, air flow rate, or other parameters, including combinations of these parameters. The set point may also be dynamic, depending upon the implementation of system120.

The physical position of sensors160may be varied from that illustrated inFIG. 13. In some embodiments, one or more sensors160may be positioned in different locations along hose130, or such sensors may be positioned inside mat126, or they may be attached to the patient support device124, such as on or adjacent top surface154.

Inflatable mats126may be constructed of any suitable materials, such as would be known to one of ordinary skill in the art. In one embodiment, mat126may be made of nylon. Other materials may also be used, or other combinations of materials. The size of mat126may also vary in order to accommodate patients and/or surfaces of different size. In some embodiments, mat126may be adapted to support up to 1000 pounds or more. Depending upon the mat size, the control algorithms implemented by motor controller158may be altered. That is, in some embodiments, motor controller158may be configured to modify its control algorithms based upon the size of the air mat. As but one example, if motor controller158utilizes a timer162to determine when mat126is initially fully inflated, the amount of time that passes before motor controller158concludes that mat126is inflated may be varied based upon the size of mat126. In other embodiments, if motor controller158is configured to maintain a threshold pressure within mat126, or to maintain some other threshold parameter, these threshold may be varied depending upon mat size. The design of motor controller158will also naturally take into account the particular operating characteristics of the motor164itself.

In still other embodiments, blower128may be further modified to include one or more actuators (not shown) that adjust one or more mechanical structures in response to the changing air needs of inflatable mat126. Such actuators may be adapted to move baffles or other mechanical structures positioned at the input port168, the output port172, or the internal conduit174within blower128wherein the physical movement of the structures changes a characteristic of the air flow in a known manner. Changes to these mechanical structures may be carried out in combination with the speed changes to motor164discussed above, or such changes may be made in lieu of speed changes to motor164. The physical movement of such mechanical structures alters the air flow to mat126in a manner that adjusts to dynamically match the air needs of mat126. As one example, blower128may include one or more physical structures within or adjacent air conduit174, or within or adjacent outlet port172, that selectively divert at least some air being blown by motor164to the ambient atmosphere. That is, instead of having all of the air blown by blower128into hose130(and consequently mat126), a portion of this air may be selectively diverted to the ambient air. Such selective diversion may result in a reduced load being placed on motor164, thereby reducing the energy consumed by motor164. The decisions as to when this air should be diverted, as well as the amount, may be based upon the feedback signals from one or more of sensors160or timer162, or any other suitable sensor or device. As noted above, such diversion of air may be the sole adjustment made to blower128in some embodiments, or it may be but one of several adjustments that blower128makes in response the feedback information supplied by sensors160and/or timer162and/or other sensors.

In any of the various embodiments discussed herein, motor controller158may be implemented with suitable electrical and/or electronic devices that are capable of carrying out the control algorithms described herein. Such electronic devices may include, but are not limited to, one or more microprocessors, integrated circuits, programmable logic devices, or any combination thereof. Blower128may also be replaced by an air pump, or other suitable device for supplying pressurized air to mat126.

The foregoing embodiments of the invention are exemplary and can be varied in many ways and, further, features of one embodiment may be combined with features of another embodiment and used in combination with features of more than one embodiment. Such present or future variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications are intended to be included within the scope of the following claims.

The disclosure of all patents, publications, including published patent applications, and database entries referenced in this specification are specifically incorporated by reference in their entirety to the same extent as if each such individual patent, publication, and database entry were specifically and individually indicated to be incorporated by reference.