Abstract:
A moisture and temperature control device on the surface of a support element of a mattress or cushion includes a casing formed by at least two parts defining an interior chamber. Capsules of one or more phase change materials (PCM) are situated in the interior chamber. The capsules have a lowest crystallization temperature that is higher than about 25° C. and have a highest melting temperature that is lower than about 40° C.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority, under 35 U.S.C. §119(a), of French National Application No. 11 54099 which was filed May 12, 2011 and which is hereby incorporated by reference herein. 
       BACKGROUND AND SUMMARY 
       [0002]    The present disclosure relates to support devices such as mattresses or cushions to support the body of a person sitting or lying on the support device, and particularly to devices such as support therapeutic mattresses to support the body of patients. More particularly, the present disclosure relates to a therapeutic mattress cover on which an individual may be lying under conditions of thermal comfort and moisture control. Thus, the present disclosure can also be considered as relating to devices and methods for the regulation of moisture and temperature on the surface of a support element such as a mattress or cushion. 
         [0003]    It is known that moisture may originate from the body of a patient by the flowing of a bodily liquid such as sweat, or an external source of spilled liquid. It is desirable to avoid the maceration of the liquid at the level of the soft tissues of the skin, whether it is external liquid or sweat, because this humidification causes maceration which may lead to the formation of bedsores and cause infectious points. 
         [0004]    Known methods and devices of this type, include injecting air at the surface or towards the body of the individual, such as by implementing so-called “low-air-loss” mattresses or cushions constituted of compartments filled with air under pressure. Thus, the body of the individual or the area between the body and the support element, i.e. the mattress, at the level where it can create moisture, is dried by the airflow sent in this direction. 
         [0005]    A primary problem of this type of known device is that it cannot be implemented independently of the support element, especially the mattress, and that the interruption of the air injection inside the mattress makes it useless. Another disadvantage of this type of low-air-loss mattress system is that it can lead to excessive drying of the body and requires compensation of water loss by a program of hydration of the individual. 
         [0006]    Dehumidification systems in the vicinity of a patient have been described, consisting of a cover comprising a casing interposed between the patient and the mattress, the casing comprising an upper layer and a lower layer defining a chamber in which air is circulated. In these systems, it is desired to dehumidify the outer surface of the upper layer on which the patient rests, at least in part, by transfer of water vapor by molecular migration of water molecules through the upper layer of the cover permeable to water vapor. 
         [0007]    In U.S. Pat. No. 5,882,349, the lower layer of the casing is impermeable to air and water vapor and air is injected where appropriate in only part of the internal volume of the casing by a plurality of injection ports, and is discharged through a plurality of perforations that may be arranged on the sides of the upper layer. This dehumidification system is relatively inefficient with an announced dehumidification of only 400 ml/24 h. 
         [0008]    In U.S. Pat. No. 5,926,884, a mattress cover of this type is described, in which the air is exclusively evacuated through perforations in the upper layer on the entire surface, and especially at the level of the zone covered by the patient, and the lower layer is permeable to water vapor. The casing so formed between the lower layer and the upper layer, both permeable to water vapor, is completed by an additional underlying layer that absorbs and disperses the water vapor that risks accumulating between the dehumidification device so formed and the mattress. 
         [0009]    In these dehumidification devices, by transfer of water vapor, the evacuation of the air, at least in part, on the side of the patient lying on the device, has the risk of contamination of the casing by penetration of liquid or another contaminant from the outer surface of the upper layer on which the patient lies. Secondly, and more noteworthy, the yield in terms of dehumidification are either relatively small or are accompanied by dehydration of the patient resulting from excessive airflow sent close to the patient. 
         [0010]    EP 1,915,978 in the name of the applicant describes a new procedure and device for moisture regulation on the surface or in the vicinity of the body of an individual lying on a support element of the type of a mattress or cushion which do not present the above inconveniences and are more performing in terms of dehumidification yield. 
         [0011]    In particular, in EP 1,915,978, the device and method can be implemented independently of the support element and particularly on any type of air or foam mattress, or other, which offers the benefit of avoiding the risks of contamination with a fluid coming from outside, and not requiring a concomitant hydration of the patient. 
         [0012]    The device in EP 1,915,978 provides an automated moisture control and not simply a device that allows only the continuous reduction of moisture like the devices of low-air-loss mattresses of the prior art. 
         [0013]    More precisely, in EP 1,915,978 a moisture control device is provided on the surface of a support element of the mattress or cushion type, in the vicinity of the body of an individual lying there, including a casing formed by at least two parts linked between them on their peripheral edges, preferably sealed by welding, defining an interior chamber, the two parts consisting of a first part or top part, intended to be arranged on the side of the body of the individual, and a second part or lower part, intended to be arranged on the side of the support member of mattress or cushion type, the first part being constituted of a material forming an impermeable barrier to air and liquid water and permeable to water vapor, and the second part being made of a permeable material to water vapor, whereby the second part comprises at least one air injection port and air discharge means comprising air-permeable perforated or porous areas, such as perforations. 
         [0014]    It is understood that the first part is not perforated and the air is exclusively evacuated through the second part situated between the first part and the support element of the mattress or cushion type. 
         [0015]    In the case of a mattress disposed horizontally on a bed, the first part constitutes an upper part on which the body of the individual lies, and the second part constitutes a lower part applied on the mattress and arranged below the first part or upper part. 
         [0016]    A device as described in EP 1,915,978 provides a satisfactory control of moisture, particularly when used on therapeutic mattresses for patient care. However, it has a thermal efficiency limit because the measured curve of temperatures of the skin of the patient lying in bed on these devices increases with time and sometimes can possibly exceed the comfort temperature of 35° C., beyond which the bedridden patient is in a state of risk of occurrence of decubitus ulcers in areas at risk of the body, such as the areas of the sacrum and heels for example. 
         [0017]    Another problem is that if the temperature of certain patients drops, especially with certain illnesses, below a lower limit temperature of 28° C., the patient&#39;s health can potentially be put in danger. 
         [0018]    The purpose of the embodiments disclosed in the present application is therefore to provide a device and method that allows simultaneous monitoring of the patient&#39;s moisture in the contact area with the mattress on which he rests, on the one hand, and, on the other hand, controlling the temperature of the patient&#39;s skin in contact with the mattress, so that it does not exceed an upper limit of about 35° C., which is the limit of comfort temperature and does fall below a lower limit temperature, about 28° C., which is the lower limit of comfort temperature. The embodiments according to the present disclosure thus reduce the occurrence of pressure ulcers resulting from the combination of the excessive moisture and temperature mentioned above. 
         [0019]    There are known materials with phase change, hereinafter PCM materials, especially fabrics coated with microcapsules of PCM materials, hereinafter PCM fabrics (e.g., marketed by the companies Outlast Technology (USA) or Schoeller Textil (Switzerland)). These fabrics are used in clothing to protect against excess heat by absorbing heat when the body produces too much or releasing it when the body is cooled. As is known, the microcapsules of PCM materials can be integrated into the fabric and even within the constituent fibers of the fabric or coated on the surface of the fabric in a coating. This technology was originally developed for NASA to protect astronauts from major temperature fluctuations in space. 
         [0020]    The inventors of the present subject matter have tried to implement such a PCM fabric juxtaposed over a humidity control device as described above. However, they observed that this arrangement, affected not only the effectiveness of regulating the reduction of moisture in contact with the patient&#39;s body, but was also less effective in limiting the rise in patient&#39;s temperature at the areas of contact with the device so constructed. 
         [0021]    In fact, the inventors have discovered that, surprisingly, the optimal implementation of a PCM fabric in combination with a moisture and temperature control and regulation device required to implement the PCM fabric under specific conditions of exposure to an airflow, is not met in the case of direct contact of the PCM fabric with the patient&#39;s body, when the PCM fabric is placed between the patient and the moisture control device as described above. 
         [0022]    According to the present disclosure, a moisture and temperature control device on the surface of the support element of the mattress or cushion type and in the vicinity of and in contact with the body of an individual lying there, includes a casing formed by at least two parts which, in some embodiments, are linked between the mat and their peripheral edges, such as by welding. The casing defines an internal chamber between the two parts. Thus, the two parts include a first part intended to be arranged on the side of the body of the individual and a second part intended to be arranged on the side of the support member of mattress or cushion type. The first part may be made of a material forming an air-impermeable barrier air and liquid water and permeable to water vapor. The second part may be made of a material permeable to water vapor. The second part has at least one air injection port and air discharge means comprising perforated or porous air-permeable areas, such as perforations. The interior chamber contains capsules of phase change material(s) (PCM) having a lowest crystallization temperature that is higher than 25° C., in some cases above 28° C., and having a highest melting temperature that is lower than 40° C., in some cases lower than 35° C. The capsules are integrated into and/or arranged on the surface of a support such as, for example, a support including a woven or non-woven fibrous material, permeable to air. In some embodiments, the PCM microcapsules have a diameter of 5 μm to 5 mm. 
         [0023]    In some embodiments, the PCM capsules are distributed in and/or at the surface of the air-permeable support at least in the contact areas of the body with the device according to the present disclosure, so that at least the contact areas are regulated in moisture and temperature, such as one or more of the contact areas of the following body parts: head, the torso area, the sacrum and heels area, when a patient lies on top of a device according to the present disclosure applied on a mattress. 
         [0024]    When the device according to the present disclosure operates, the airflow circulates inside between the lower part and the upper part with the PCM capsules being initially in solid phase in normal temperature and pressure conditions (e.g., 25° C., 1 atm). 
         [0025]    After the patient has been in bed for a few minutes, the temperature of the surface of the patient&#39;s skin will tend to increase due to heat accumulation. Thus, the skin temperature will increase and tend towards uncomfortable temperatures beyond 35° C. When the patient is in indirect contact with the PCM capsules, whose temperature change phase is between about 20 and about 40° C. on contact, the PCM capsules will change their state from solid to liquid if their temperature reaches the highest melting temperature mentioned above. Indeed, this phase change of the material requires energy, called “latent heat,” carried by the heat generated by the patient, and uses the energy available, this excess heat created by the patient. The temperature of the patient&#39;s skin then tends to stabilize in a comfort zone not exceeding the limit temperature mentioned above, because the excess heat is evacuated. 
         [0026]    Thanks to these PCM capsules in combination with an airflow inside the chamber, a temperature gradient is created between the patient and inside the device, resulting in a spontaneous transfer of heat from the patient to the interior of the device. 
         [0027]    Conversely, if the temperature of the patient&#39;s skin is reduced because of a disease and drops below the comfort zone (e.g., below about 25° C., or in some cases below about 28° C.), the PCM in indirect contact with the patient return from liquid to solid state by releasing the latent heat which warms the patient to maintain the patient in the comfort temperature range above about 25° C., or in some cases above about 28° C. 
         [0028]    A balance is thus created within the device and the surface of the patient&#39;s body. In some embodiments, the skin temperature does not exceed about 40° C., or in some cases about 35° C. and stabilizes in a comfort zone between about 25 and about 40° C., or in some cases between about 28° C. and about 35° C. The patient&#39;s body temperature is thereby controlled, with the temperature differences being fairly limited. 
         [0029]    On the other hand, when the patient lies down on the operating device, it sometimes creates high humidity in the upper part near the patient. Thus, a moisture gradient is created between the top of the upper layer and underneath this layer; water molecules in vapor phase will therefore pass through the upper layer, from the patient towards the inside of the device. Indeed, this upper part allows migration of water molecules in the vapor phase due to the chemical nature of the molecules of the upper part. Positive and negative charges alternate on the molecules of the top part and water vapor molecules may interact with the molecular chain, in particular the polyurethane of the upper part by hydrogen bonding, and thus move along this molecular chain. Thus, the water molecules go through the top part and find themselves inside the device. They are then driven away by the airflow. In the end, there is a reduction of moisture of the patient. 
         [0030]    The airflow within the chamber increases the efficiency of the PCM by absorbing part of the heat energy from the patient. On the other hand, the heat absorption by the PCM contributes to increased moisture decrease due to the reduction of the patient&#39;s perspiration. Consequently, there is a synergistic effect between the specific means of moisture reduction that are the first and second parts and airflow and the specific means of temperature control that are the PCM capsules. 
         [0031]    The combination of humidity regulation and temperature control with the device according to the embodiments of the present disclosure thus significantly reduces the risk of pressure ulcers. 
         [0032]    Another feature of the device according to the present disclosure is the ability to regulate or control the temperature without having to implement a device for heating and/or cooling the air injected into the chamber, which devices require a supply of energy to operate. 
         [0033]    According to this disclosure, the phase change materials can be organic materials such as fatty alcohols or fatty acids, glycols, or in some embodiments, paraffinic hydrocarbons or inorganic PCM, such as hydrated salts. Also according to this disclosure, PCM capsules or microcapsules of about 10 μM to about 5 mm may have a hollow spherical polymeric wall which is about 1 to about 50 μM thick. 
         [0034]    According to some embodiments, the capsules are microcapsules with diameters between about 10 to about 500 μM, such as between about 25 to about 100 μm, fixed, such as at regular spaces, within and/or on the upper surface of a so-called air-permeable support. 
         [0035]    In some embodiments, the PCM include paraffinic hydrocarbons having at least one chain in C-14, of which a first PCM whose phase change temperatures are between about 25° and about 30° C., such as alkane, and a second PCM whose phase change temperatures are between about 30° and about 35° C., such as lycosane. 
         [0036]    In some embodiments, therefore, the device comprises at least two PCM-type materials, of which a first PCM has a crystallization temperature that is lower than that of the second PCM, comprised between about 25° and about 30° C., such as between about 28° and about 30° C., and of which a second PCM has a melting temperature that is higher than the melting temperature of the first PCM, comprised between about 30° and about 40° C., such as between about 32° and about 35° C. 
         [0037]    According to some embodiments, the PCM microcapsules are applied above and/or within a so-called support constituting an intermediate layer permeable to air and to water vapor, forming a fabric referred to as 3D fabric or constituted of a nonwoven highly porous fibrous material, the intermediate layer being thicker than the first and second parts, such as from about 5 to about 50 mm thick. 
         [0038]    The 3D fabric may comprise known materials having three dimensions, which are unlike textiles that are woven in two dimensions (flat). Thus, 3D fabric has a certain thickness, corresponding to the weaving of the third dimension. Some of these materials have high porosity by their constitution and are therefore permeable to air. Finally, as mentioned above, they provide a technical effect of mechanical protection of the PCM microcapsules. 
         [0039]    This thick intermediate layer also promotes the spacing of the first and second parts and facilitates air circulation inside the chamber and therefore facilitates better diffusion and better evacuation of water vapor. This intermediate part included inside the chamber also has the effect of avoiding climate bridges between the first and second parts and allows for better airflow. 
         [0040]    In some embodiments, therefore, the thick intermediate part includes a layer of a nonwoven fibrous material, such as polyester wadding, and in some instances is held in shape by a holding device, for example a net and/or a grid of quilted-type seams. 
         [0041]    The thick intermediate layer has an absorbing effect favoring a better distribution and spread of moisture and therefore a better distribution of moisture in the interior of the chamber, moisture being thus more rapidly cleared by air injected inside the chamber and inducing a more efficient dehumidification. 
         [0042]    The inventors have discovered that having this type of 3D intermediate layer is favorable (although not required) since the nonwoven fibrous material allows the microcapsules to sink without crashing under the weight of the patient&#39;s body, whereas in the absence of this layer of intermediate nonwoven fibrous material, after some time it is noticed that the microcapsules are crushed under the weight of the patient&#39;s body. 
         [0043]    It is contemplated by this disclosure that the device may also comprise an intermediate sheet of nonwoven fibrous material, coated at least on its upper surface with the PCM microcapsules, the microcapsules having a diameter of about 10 to about 500 μm, such as about 25 to about 100 μm, and being dispersed at the rate of about 10 5  to about 10 7  microcapsules/cm 2 , such as about 10 6  to about 5×10 6  microcapsules/cm 2 , the intermediate sheet being thinner than the first and second parts, and having a surface density of about 100 to about 200 g/cm 2 . 
         [0044]    Alternatively or additionally, the interior chamber comprises an intermediate sheet of thin nonwoven fibrous material, coated on at least its upper face with the PCM microcapsules. In some embodiments, this thin intermediate sheet is situated over the upper surface of the thicker intermediate layer of a nonwoven fibrous material, permeable to air and to water vapor. 
         [0045]    According to other characteristics, one or more of which may be included in some embodiments of the device: 
         [0046]    the water vapor permeability of the second part is less than that of the first part; 
         [0047]    the evacuation means comprise the perforations, arranged with respect to the injection port(s) so as to be capable of creating an airflow entering the chamber through the injection port and evacuated from the chamber via the evacuation means, such as the perforations, throughout the volume of the chamber, when the casing is inflated by pressurized air injected continuously via the injection port, so as to create an overpressure in the chamber; 
         [0048]    the second part is substantially airtight between the injection port and the porous or perforated areas permeable to air, the latter being arranged sufficiently far away from the injection port(s) for substantially the entire volume of the chamber to be crossed by circulating air between the injection port(s) and the porous or perforated areas; 
         [0049]    the first part includes a porous or perforated substrate non-impermeable to water and air, the substrate being coated on at least one side with a continuous layer of polymer, such as polyurethane, not permeable to liquid water and air, and having molecular transfer properties of water vapor; and/or 
         [0050]    the second part consists of a fabric coated on at least one of its faces with a layer of polymer, such as polyurethane, having properties of molecular transfer of water vapor, such as on the face facing the chamber. 
         [0051]    For the first part, a perforated porous substrate such as a fabric constructed by weaving fibers or threads has porosities or perforations not creating a barrier to the passage of water vapor transferred through the layer of polyurethane polymer. 
         [0052]    Polymers and textile materials of this type with transfer of water vapor are known and are commercially available and are used, particularly in the garment industry for their breathing quality and body disposal/regulation of sweating. 
         [0053]    This property of molecular water vapor transfer of the polymers results from molecular affinity inducing attraction of water molecules on the molecular chains of the polymer, particularly polyurethane, comprising hydrophilic groups, the water molecules being able to move along the polymer chain and cross through the layer of the polymer. 
         [0054]    In some embodiments, the second part includes a fabric coated on at least one of its faces with a layer of polymer permeable to water vapor, i.e. having molecular transfer properties of water vapor, such as on the side facing towards the interior of the chamber. 
         [0055]    In some embodiments, the first and second parts are connected together on their peripheral edges by welding, directly with each other, or via a connecting strip coated with a polymer layer, the different polymer layers of the first and second parts and of the strip, where appropriate, being welded together by heat sealing or welding by irradiation, such as high-frequency irradiation. 
         [0056]    In some embodiments, the different polymer layers are of the same chemical nature, or of a chemical nature suitable to permit them to be welded together, which is the case of polyurethane polymers. 
         [0057]    The two parts may be polymer-coated on both sides, and be sealed to one another directly. The two parts are in some instances, for economic reasons, polymer-coated on one side only. And, if at least one of the faces of the two parts is not polymer-coated, such as if the first part is polymer-coated on its outer face and the second part on its inner face, the edge of one of the two parts can be folded on itself so as to have its face polymer-coated towards the inside of the chamber. 
         [0058]    In some embodiments, it is also possible to implement a peripheral connecting strip eventually folded on itself, providing the link by welding between the first and second parts, the strip being itself coated on one side at least with a layer of polymer which can be welded with the polymer layers of the two the first and second parts, the polymer layer of the strip being of the same impermeable nature to liquid water, air and water vapor as that of the second part. 
         [0059]    In some embodiments, the fabrics constituting the first and second parts are fabrics that stretch in both longitudinal and transverse directions. Specifically, this feature allows improving the distribution of body weight, i.e. on its larger surface, and the fabric hugs the body shape and does not generate localized areas of excessive compression of the body that can generate vascular blockages and resulting diseases. 
         [0060]    In some embodiments, the air evacuation perforations are arranged on the periphery of the second part. These peripheral areas do not coincide with the central area of the casing with which the body is normally in contact, but around it, thereby facilitating the evacuation of the air through the perforations. 
         [0061]    In some embodiments, the second part is of substantially rectangular shape and the device comprises a single injection port near the middle of a longitudinal edge of the second part, the air evacuation perforations being disposed near the side edges and the longitudinal edge opposite to that of the injection port. 
         [0062]    Thus, the injection port is disposed relative to the evacuation perforations so as to make air circulate well throughout the inner chamber of the casing and drain out as quickly as possible the moisture transferred from the vicinity or the surface of the body towards the interior of the chamber. 
         [0063]    This disclosure also provides a method for controlling the temperature and moisture on the surface of a support element such as a mattress or cushion and in the vicinity and contact of the body of an individual lying there, using a device according to the present disclosure, characterized in that: 
         [0064]    1) the casing is placed flat between the support element and the body of an individual, so that the first part is turned towards the body of the individual and the second part is turned towards the support element, and 
         [0065]    2) air under pressure is injected into the chamber by the injection port at a pressure and at a rate such that the casing is inflated in overpressure despite the evacuation of air by the evacuation means, such as by the perforations and the support of the body on the casing, the air overpressure inside the casing relative to the outside being sufficient to allow air circulation throughout the volume of the chamber. 
         [0066]    It is understood that the air is injected at a pressure and at a rate such that the air within the chamber is in overpressure versus the ambient air in the room. 
         [0067]    By the properties of water vapor permeability of the first part, a transfer of water vapor takes place through the first part when a relative humidity gradient exists between the outer surface of the first part of the casing and the interior of the chamber, especially in case of maceration of a liquid or sweating of the body or close to the body between the body and the casing, which is accompanied by a dehumidification of the surface of the first part. When the humidity is equal on both sides of the first part, i.e. between the exterior and interior of the casing, there is no more relative humidity gradient and the transfer of water vapor stops automatically. But air circulation inside the casing allows driving the water vapor, evacuating it outside through the second part. This circulation promotes a decrease of the relative humidity within the casing and maintains the transfer of water vapor from outside the casing towards the inside of the casing where appropriate, as long as the moisture outside it is greater than relative air moisture within the casing and therefore than the moisture of the ambient air injected. The fact that moisture outside the surface of the casing is reduced until reaching the value of relative humidity of the ambient air injected, and the water vapor transfer is interrupted automatically at that time, avoids excessive dehydration of the skin tissues of the body. In addition, because of the permeability properties of the water vapor of the second part, the vapor transferred within the chamber can be evacuated to the outside in spite of the air circulation, which keeps and promotes the establishment of a high relative humidity gradient between the outside of the first part and the interior of the chamber. 
         [0068]    Finally, the fact that the second part is permeable to water vapor, and that the air is exclusively evacuated through the second part, provides a process of dehumidification by transfer of water vapor by molecular migration through the device, with a transfer rate of water vapor and thus dehumidification higher than in the prior art, without undue dampness below the device between the second part and the mattress, without risk of contamination by ingress of contamination or of liquid from the upper outer surface of the first part, since it is non-perforated, and finally, without requiring concomitant hydration treatment of the patient as is the case when air is evacuated from the upper layer towards the patient or close to the patient. 
         [0069]    Moreover, because according to this disclosure, air is evacuated through the second part or bottom layer, the water vapor transferred to the underside of the second part or bottom layer does not accumulate between it and the mattress on which it is disposed, and is evaporated by the air evacuated, which is thus injected therein. 
         [0070]    As explained above, the addition of the PCM layer stabilizes the temperature of the skin (and therefore of the body) and consequently limits perspiration. On the other hand, there is a synergistic effect whose mechanism is not fully understood, in that the air circulation of the device surprisingly boosts the effectiveness of PCM microcapsules, resulting in a more efficient cooling than in the absence of air circulation. 
         [0071]    In some embodiments contemplated by this disclosure, the water vapor permeability of the second part is less than that of the first part. 
         [0072]    This limited water vapor permeability of the second part avoids the accumulation of moisture between the second part and the support element and allows the evaporation of this moisture primarily by the airflow from the means of air evacuation in the absence of injection of additional air between the second part and the support element. 
         [0073]    In some embodiments, the second part is substantially airtight between the injection port and the porous or perforated areas permeable to air, the latter being disposed sufficiently away from the injection port so that substantially the entire volume of the chamber is crossed by air flowing between the injection port and the porous or perforated areas. 
         [0074]    In some embodiments, according to the present disclosure, the ratio between the cumulative sections of the evacuation perforations and the injection ports section is selected so as to obtain a compromise between, on the one hand, the search for an airflow rate circulating through the high chamber and, on the other hand, a sufficient overpressure within the chamber. Indeed, the overpressure should be sufficient to ensure that the injected air circulates throughout the chamber volume, i.e. that the air is evenly distributed throughout the volume of the chamber. Otherwise there is a risk that the injected air is limited to travel within the chamber only between the injection port(s) and those of so-called localized perforated or porous areas corresponding to the passage of minimum pressure drop. 
         [0075]    However, we understand that the overpressure should also be limited so as not to destabilize the individual&#39;s body resting on the casing. 
         [0076]    In practice, a pressure of at least about 500 Pa provides a homogeneous air circulation in all directions and in particular in the area below or vis-à-vis the patient&#39;s body. 
         [0077]    On the other hand, the upper limit of airflow circulating in the chamber is related to the maximum rate of vacuum, i.e. the cumulative section of ports that can be tolerated by the material of the second part from a viewpoint of its mechanical strength. This rate should not exceed about 10% in general. Furthermore, it should be taken into account that the positive effect of increased airflow on dehumidification performance is limited by the capacity of the water vapor transfer of the first and second layer piece. Beyond a certain airflow, the dehumidification performance is not improved. 
         [0078]    In practice, a flow rate of about 20 to about 50 l/min provides adequate dehumidification performance given the time of migration of water molecules for the transfer of water vapor through the polymer layers implemented as described below. 
         [0079]    More particularly, for an overpressure of about 500 to about 1000 Pa with an airflow rate of about 20 to about 50 l/min, the ratio of the sum of the sections of perforations or pores of the porous perforated or respectively discharge areas of air evacuation relative to the sum of the sections of the injection ports is at least 2, and in some cases 2 to 4. 
         [0080]    The evaporation of the surface water on the side of the patient is accompanied by a slight decrease of the temperature which promotes a reduction in sweat and, in some instances, offsets the increase in temperature resulting from the compression of the air injected. 
         [0081]    More particularly, the transfer of water vapor from the first part is at least about 750, such as about 750 to about 2000 g of water/m 2 /24 h, further such as about 1000 g of water/m 2 /24 h and the transfer of water vapor of the second part is less than about 500 g of water/m 2 /24 h, such as about 300 to about 500 g of water/m 2 /24 h. 
         [0082]    In some embodiments of the method according to the present disclosure, an overpressure of air is established within the chamber with respect to the exterior of the chamber, sufficient for air to circulate throughout the volume of the chamber and more particularly an overpressure of about 500 to about 1000 Pa is established, such as about 750 Pa, with an airflow rate circulating in the chamber of at least about 20 l/minute, such as about 30 to about 50 l/min. 
         [0083]    According to this disclosure, the device comprises a device injecting compressed air which supplies air to the casing by the injection port. 
         [0084]    Also, in the method according to the present disclosure, air is injected between the second part and the support element, such as from the same device injecting compressed air supplying the casing through the injection port. 
         [0085]    In some embodiments, the support element includes at least one inflatable compartment filled with air, and if desired, connected to the same air injection device as the one supplying the casing. 
         [0086]    The air filling the chamber can thus be derived from the same air source as that inflating the mattress via a device guiding the air selectively, for example a solenoid device acting as switching device of a single air source. For example, a solenoid valve may be part of a module cooperating with the device according to the present disclosure. 
         [0087]    Facilities for injecting air into an inflatable mattress have been described especially in applicant&#39;s patents EP 676,158; FR 2,751,743; FR 2,757,377; FR 2,757,378; FR 2,758,259; and FR 2,760,967. 
         [0088]    In some embodiments, the device according to the present disclosure may also include a remote control system, especially remote control of the device injecting compressed air. 
         [0089]    In some embodiments, the device of the present disclosure is incorporated into a protective cover of the support element of mattress or cushion type, at least at the part of the cover that covers the part of the face of the support element on which at least part of the body of an individual is intended to rest. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0090]    Other features and characteristics of this subject matter will become apparent from the detailed description which follows and  FIGS. 1 to 6 , in which: 
           [0091]      FIG. 1  shows a schematic longitudinal section of an inflated air mattress covered with a protective cover incorporating the control device according to this disclosure, on which a patient rests; 
           [0092]      FIG. 2  shows a schematic view of four parts comprising a control device  1  according to the present disclosure; 
           [0093]      FIG. 3  shows schematically in cross section a method of welding of the bottom part over the top part via a strip forming the lateral rim, of a cover that ends with a closure/opening device with slide and also forming a flap for protecting a closing/opening device; 
           [0094]      FIG. 4  is a schematic representation of a fabric incorporating evenly spaced microcapsules over the entire surface of the fabric, the fabric being sewn by mattress stitching and a peripheral serging over a thicker layer porous to air; 
           [0095]      FIG. 5  shows measurement curves of the temperature of the skin in ° C. under the patient lying on top of a device according to the present disclosure over a mattress, as a function of time (t) in seconds, in which curve A represents an embodiment in which the device comprises a PCM fabric sewn over a layer of polyester wadding, the regulating device being crossed by an airflow in the chamber, in which curve B corresponds to the same embodiment with PCM fabric and airflow, but without layer of cellulose wadding in the chamber, in which curve C represents the same embodiment as the curve B but without the airflow, and in which curve D represents the same embodiment as the curve A with airflow but without PCM fabric; and 
           [0096]      FIGS. 6A ,  6 B and  6 C are perspective views ( FIG. 6A ), in detail ( FIG. 6B ) and exploded ( FIG. 6C ) of a second embodiment of a device according to the present disclosure, that can be applied having a bottom piece  12 , with a peripheral skirt  12 - 1 , capable of covering the lateral edges of a mattress  13  on which the device  1  is applied as is, the top part  11 , also comprising a peripheral skirt  11 - 1  thermo-welded to the upper peripheral edge of the bottom part  12 . 
       
    
    
     DETAILED DESCRIPTION 
       [0097]      FIGS. 1 to 3  show a control device according to the present disclosure comprising a casing  1  made of two parts: an upper part or the first part  1   1  and a lower part or the second part  1   2 , whose peripheral edges  1   a  and  1   b  are welded  1   c  together by means of a connecting strip  6  folded on itself, the weld lines  1   c  following substantially a rectangular contour. 
         [0098]    The casing  1  of a control device according to some embodiments of this disclosure is incorporated into a protective cover  7  covering an air mattress  13 . More particularly, the casing  1  forms the upper face of the protective cover, and a portion of the connecting strip  6  forms lateral edges  6   1  of the protective cover partly covering the sides of the mattress  13 , the lower second part or the second part  1   2  being applied directly on the mattress  13 . 
         [0099]    The upper and lower parts are of substantially rectangular shape corresponding substantially to the dimensions of the mattress. The cover includes a device for closing/opening with peripheral zipper  6   2  along the lateral sides or edges of the cover covering the edge of the mattress, the closure/opening  6   2  allowing the separation of a lower part  7   1  of the cover and lateral edges  6   1  and the removal of the mattress from the cover. 
         [0100]    The top part or first part  1   1  includes a polyester fabric coated on its upper external face with polyurethane polymer that has properties of transfer of water vapor. 
         [0101]    More specifically, these polyurethane polymers are comprised of molecular chains of polyurethane containing hydrophilic ester groups allowing the transfer of water vapor by molecular migration of water molecules through physico-chemical interaction with the hydrophilic ester groups of the molecular chains. 
         [0102]    Some such fabrics coated on one side with polyurethane with transfer properties of water vapor are marketed under the brand Dartex®, particularly in the reference P510, with properties of water vapor transfer of about 1000 g of water/m 2 /24 h (amount of water transferable through the coated fabric), and comprising a composition of about 66% polyester and about 34% polyurethane, and a grammage of about 130 g/m 2 . 
         [0103]    The lower part or second part  1   2  includes a polyamide-based nylon fabric coated on one face with a polyurethane coat permeable to water vapor, marketed by the company Dartex®, especially under reference P280, with a water vapor transfer rate of about 350 g of water/m 2 /24 h, a composition of about 47% polyamide and about 53% polyurethane, and a grammage of about 179 g/m 2 . 
         [0104]    The casing formed by the two lower and upper parts defines an internal chamber  1   3 . Inside the chamber, a first intermediate part  2  is inserted, substantially occupying the entire volume of the chamber of substantially rectangular shape, comprising a layer of a nonwoven material  2   1  of about 5 to about 10 mm thick, constituting a duvet based on cellulose wadding of about 150 to about 200 g/m 2  and further constituting an absorbent material permeable to air and water. One can use in particular a 3D fabric of AMES EUROPE reference Pro643/3. This interlayer has the dual property to divide and distribute the homogenized water vapor transferred inside the chamber from the outer surface of the upper part, and provide a spacer between the upper and lower parts to prevent contact between two parts, while also providing some mechanical protection of the PCM microcapsules described below. 
         [0105]    The first intermediate part of non-woven material  2  is covered with a plastic mesh  2   1  of tulle with polyester fibers type. A peripheral seam unites the layer of the intermediate part with the net, preferably in longitudinal and lateral grid seams, stabilizing the shape of the first intermediate part. 
         [0106]    A second intermediate part  3  consisting of a fabric, hereinafter referred to as “PCM fabric,” is sewn on the upper face of the first intermediate part. The PCM fabric  3  is sewn in grid on the surface of the 3D fabric  2 , so that it does not fold and does not move when one packages, for example, or wraps, bends and/or wraps the entire device for transport. The fabric PCM  3  includes a layer of nonwoven polyester, coated with an acrylic coating containing microcapsules  4  of PCM. The microcapsules  4  have a diameter  4  of about 40 μm. The microcapsules have a spherical membrane wall of approximately about 2 μm in thickness, including the PCM. In some embodiments, the PCM fabric  3  includes more specifically about 3,000,000 microcapsules/cm 2 . A suitable PCM that can be provided in the microcapsules includes a mixture of paraffinic hydrocarbons, namely alkane and lycosane whose respective melting temperatures are about 28 and about 33° C. 
         [0107]    This PCM fabric  3  is permeable to air and water and has a surface density (including with the PCM microcapsules) of about 140 g/m 2  in the illustrative example. A PCM fabric  3  of this type is marketed by Outlast Technology (USA) under the commercial reference 233 Outlast 901 greeley. PCM fabrics of this type are also marketed by Schoeller Textil (Switzerland). 
         [0108]    In some embodiments, air is injected so as to create an overpressure of about 750 Pa in the casing  1  with respect to outside air by establishing a balanced incoming airflow and outgoing airflow of about 25 to about 35 l/minute. To do this, the bottom part  1   2  includes an air injection port  5   a  in the center of about 9.5 mm diameter and near a longitudinal edge of the bottom part  1   2 , the air injection port including a welded plastic connector in some embodiments. Perforations for air evacuation with a diameter of about 3 mm are regularly spaced about 10 to about 20 cm along the other three edges of the bottom part  1   2 , i.e. the two transverse edges and the longitudinal edge opposite to that of the injection port. For a bed of about 2 m long and about 90 cm wide, 48 perforations were thus made. The cumulative sections of the evacuation perforations  5  thus represent approximately double the section of the injection port  4 . Thus, it compensates for losses of charge related to restrictions on the passage of air and maintains a balance between the incoming and outgoing airflow with this rate of about 25-35 l/min and this overpressure of about 750 Pa of air in the chamber versus the outside. 
         [0109]    The air injection port  5   a  is supplied by a compressor  8  which also supplies the air mattress  13  by means of a solenoid valve  9  which serves as a switch controlled by a control device  10 , either for the air supply  12  of mattress  13  or for the air supply  11  of the air injection port within the chamber, based on measurements of a mattress inflation pressure sensor in particular. 
         [0110]    The control device according to the present disclosure thus allows drying about 500 ml of water spread evenly over a cotton sheet with the dimensions of the mattress, i.e. about 2 m 2  in about 3.5 hours when the mattress is covered with a model simulating a patient&#39;s body in the presence of the first and second intermediate parts  2 ,  3  and in about 6 hours in the absence of the first intermediate part  2 , the tests having been performed in an ambient atmosphere of about 40% relative humidity at ambient temperature of about 25° C. 
         [0111]      FIG. 5  shows several measurement curves of the temperature of the skin under the patient  14  in contact on a mattress  13  equipped with a device for regulating the moisture and temperature  1  under the following conditions: 
         [0112]    curve A=a device  1  comprising a PCM fabric  3  combined with a thick layer of porous cellulose wadding  2  with an airflow created as described above; 
         [0113]    curve B=a same device  1  with a same PCM fabric  3 , but in the absence of the thick layer  2  with the same airflow; 
         [0114]    curve C=same device  1  as curve B, but without airflow; and 
         [0115]    curve D=same device  1  as curve A, but without the PCM fabric  3  and with the same airflow. 
         [0116]    We see that only the curves A and B remain below about 35° C. over time, while for curves C and D the skin temperature exceeds 35° C. after a few minutes. 
         [0117]    The comparison of curves A to D shows that: 
         [0118]    the implementation of a PCM fabric  3  can effectively control the temperature in combination with air circulation and therefore means allowing for the airflow through the upper and lower layers in particular; and 
         [0119]    even more so, the most dramatic limitation of temperature (curve A) is obtained under conditions favoring the best airflow by the presence of a thick porous layer  2 ; and 
         [0120]    in the absence of PCM fabric with airflow (curve D) or in the presence of PCM fabric without airflow (curve C), it is not possible to keep the temperature below about 35° C. when the device is constructed as explained above. 
         [0121]    To achieve the curves A to D in  FIG. 5 , the ambient temperature was about 25° C. Comparative tests have shown that the control device  1  according to the present disclosure allows drying about 500 ml of water spread evenly over a cotton sheet as described above in about seven hours, when the mattress is covered by the body of a patient and the device  1  comprises only a second intermediate part  2 , in ten hours when the second intermediate part  2  is combined with a PCM fabric  3 . Tests were performed under the same conditions of ambient humidity and ambient temperature as described above. We deduce that the more rapid dehumidification with a PCM fabric  3  is probably due to reduced sweating of the patient&#39;s body. 
         [0122]    We see that, in the absence of PCM fabric  3 , device  1  provides a moisture control but has limited thermal efficiency, because the measured temperature curve of the skin of a bedridden patient on the device increases with time and exceeds the comfort temperature of about 35° C. in the absence of PCM fabric  3 . Therefore, beyond this temperature, the bedridden patient is in an enhanced state for occurrence of pressure ulcers in areas of the body at risk, such as the area of the sacrum and that of the heels, for example. The PCM fabric implemented on a thick layer  2 , in combination with an airflow, allows the skin temperature to remain within the comfort zone, between about 28 and about 35° C. 
         [0123]    This results from the fact that PCMs include a mixture of the following two PCMs: 
         [0124]    a first PCM, whose lowest crystallization temperature is greater than about 28° C., so that a portion of the microcapsules of the first PCM is in solid state at the temperature of about 28° C. and if the temperature in contact with the patient and the device  1  according to the present disclosure falls below about 28° C., the first PCM solidifies and releases heat, while 
         [0125]    the second PCM has the highest melting temperature lower than about 35° C., namely about 33° C., so that if the temperature in contact with the patient and the device  1  rises above about 35° C., the second PCM melts and absorbs heat. 
         [0126]    On the other hand, the comparative curves (B) and (D) in  FIG. 5  show that the same PCM  3  fabric without the first intermediate part of polyester batting  2  (B) can still maintain the temperature of the skin under the patient below about 35° C. provided that it is combined with an airflow. Indeed, in the absence of airflow in the presence of PCM fabric  3  but without polyester padding  2 , the curve (D) exceeds about 35° C. 
         [0127]    The phase change of the PCMs requires energy called “latent heat.” We see that the combination of these two PCMs has the effect of limiting the temperature differences and tends to keep them in a narrow temperature range corresponding to a comfortable temperature. 
         [0128]    The combination of the PCM fabric  3  with an airflow (curve A) and even more so with a thick porous layer  2  (curve B), increases the effect of stabilizing the temperature below 35° C. with respect to a same device without air and with PCM fabric  3  (curve C) and even more so when compared to the same device without PCM fabric  3  and with air (curve D). 
         [0129]    The presence of a PCM fabric  3  in combination with an airflow, while the airflow is promoted in the presence of a thick porous layer, helps regulate the patient&#39;s body temperature within a range of reduced temperature difference between about 28° C. and 34.5° C. But, moreover, the combination of PCM fabric  3  with an airflow and more so in combination with a thick porous layer  2 , reduces even further the moisture rate in the upper layer in the vicinity of the patient, because temperature control allows avoiding, or in any case, greatly reducing the perspiration of the patient. 
         [0130]    In the  FIG. 1  example, the connection by welding of the lower parts  12  and upper part  11  is made through connecting strips  6 . Specifically, a connecting strip  6  including a fabric coated on one of its faces with a layer of polyurethane polymer and having the same properties of impermeability to air, water and water vapor is folded over itself to be welded to both the peripheral edge  1   a  folded on itself of the top part  11  and on the peripheral edge  1   b  of the lower part  12 . 
         [0131]    The connecting strip  6  thus comprises 2 parts folded on each other, comprising since the welding  1   c  with the bottom part  1   2  a part forming a side flange  6   1  of the mattress  13  and ending with a zipper closing device  6   2  which opens to allow removing the mattress out of the cover  7 . The side flange  6   1  covers the sides of the mattress  13 . The other part of the strip extending from the weld  1   c  with the top part  1   1  is a flap  6   3  covering the side flange  6   1  and the zipper closing device  6   2  so protected. 
         [0132]    In some embodiments, the casing comprises a further opening/closing device with zipper, not shown, impermeable to air and water of the type of the devices used to reversibly seal bags of food, thus permitting the opening of the casing and removing the first and second intermediate parts  2  and  3  for regular cleaning. 
         [0133]      FIGS. 6A ,  6 B,  6 C show a second simplified embodiment, in which the control device  1  according to the present disclosure acts as a protective cover of a mattress by applying directly to the underside of the second part  12  over the upper face of the mattress  13 , the peripheral skirt  12 - 1  of the first part  12  which serves to protect the vertical side edges of the mattress  13 . 
         [0134]    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.