Abstract:
In a convective treatment system a wind-actuated instrument mounted near an end of an air hose provides, generates, issues, or sounds an audible alarm when the end becomes disconnected from a convective device and pressurized air continues to flow through the end. The instrument may be mounted on an interface device receivable on the end. The interface device may include means for reducing or stopping the flow of air through the end in response to the disconnection.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to safety measures in the convective treatment of persons. The invention also relates to audibly indicating a condition threatening injury to a person during convective treatment. Such a condition might occur when an air hose is disconnected from a convective device, which can pose the danger of injury resulting from discharging pressurized, thermally-conditioned air from the air hose directly onto the person. 
     BACKGROUND OF THE INVENTION 
     A convective treatment system typically consists of at least a temperature-control/blower unit (known simply as a “blower”), a ducting system, and a convective device such as a convective warming blanket. A blower aspirates air from an ambient environment, changes its temperature to a desired value, pressurizes the air above the ambient pressure, and discharges the air at an exhaust port. U.S. Pat. No. 6,126,393 describes such a blower and associated temperature and noise control schemes. In an exemplary convective treatment system, pressurized, thermally regulated air produced by a blower is conveyed through a ducting system and delivered to a convective device, such as a convective warming blanket, that distributes the thermally regulated air around a person or a specific body area of a person. Such treatment is frequently used, for management or modulation of the person&#39;s body. core temperature. For example, convective thermal treatment is particularly effective in preventing or mitigating hypothermia. 
     A convective device may be embodied, for example, in an inflatable device which inflates with pressurized, thermally regulated air and has one or more surfaces adapted for expelling air onto a person. Such devices may lie on, around, or under the person. A convective device is generally realized as a blanket, but can be embodied by other appliances or attachments that are designed to be operated by or with the application of pressurized, thermally conditioned air. When used herein, the term “convective device” is intended to include all blankets, pads, covers, manifolds, and equivalent structures that operate as just described. Irrespective of orientation, a convective device utilized for convective thermal treatment of persons performs at least three basic functions. These functions are 1) the conveyance of thermally conditioned air from at least one inlet port into the device, 2) the imposition of a heat gain or loss that changes the temperature of the thermally conditioned air, and 3) the extravasation of the thermally conditioned air from the device. In the following discussion, the assumption is that such a convective treatment device is operated to warm a person by delivery of heat to the person. 
     In those convective treatment systems which treat a person by the application of heat, heat may be transferred by convection, radiation, and conduction, but convection generally predominates at the interface between the convective device and the person. The rate of convective heat transfer depends on material properties, surface boundary conditions, and significantly, fluid velocity. 
     Heat is lost from a convective treatment system whenever a temperature gradient exists between it and the ambient environment. During normal operation of the system, the temperature of the air expelled onto the person is maintained at a level that is generally higher than the person&#39;s skin surface temperature, but not high enough to cause tissue damage. In order to counter the loss of heat from the system, however, the air is heated initially to a temperature that may exceed the thermal damage threshold at the target site on the person&#39;s skin. Within certain limits, the amount of heat lost from the system is predictable. This predictability allows the system to operate safely by measuring and controlling the temperature at the proximal end of the air supply duct that connects the blower to the convective device. If any factors upon which the assumption of predictability depends are altered, however, the fluid temperature at the distal end of the duct system may be affected. 
     Several intrinsic and extrinsic factors contribute to the rate of heat loss from a convective treatment system. Among the intrinsic factors are the surface area and material characteristics of the duct and convective device, and the residence time of the warmed air within the duct and convective device. Extrinsic factors include, but are not limited to, ambient temperature and air velocity in the area immediately adjacent to the duct and the convective device. The residence time of the heated fluid within the system is a function of its pressure and the resistance exerted by the entire system. Factors that influence resistance are the duct diameter and length, the orientation of the duct, and the resistance of the convective device or devices. 
     One hazard associated with the use of convective treatment is burns. First-, second-, and third-degree burns have occurred through the improper use of convective treatment systems. The bum hazard is accentuated by the intentional or accidental alteration of the intrinsic or extrinsic factors that moderate the heat loss in the system. The alteration of any of these factors introduces an unpredictable amount of heat loss into the system, which can significantly alter the temperature or velocity of the heated air delivered to the person. One of the more important factors that influence the temperature of warm air flowing out of the air supply duct through the end where it connects to the convective device is the residence time of the air within the duct. The end through which air flows out of the air supply duct is usually referred to as the “distal end” of the air supply duct. Typically, a nozzle may be mounted to this end. The temperature of pressurized warm air exiting the duct at this end is called “nozzle temperature” (whether or not a nozzle is mounted thereto). In general, a decrease in residence time of the pressurized warmed air is usually associated with an increase in the nozzle temperature of the air. 
     In the field, a common misuse of one or more components of a convective treatment system may occur. Either intentionally or accidentally, some users fail to connect the convective device to the distal end of the duct and allow the heated air discharged from the distal end to make direct contact with the person. In view of the fact that an air supply duct is typically embodied as an air hose, this practice has come to be known as “hosing” or “free-hosing.” In other cases, operators have failed to connect the convective device to the duct and allowed the heated duct to make direct contact with the person&#39;s skin. In still other cases, frequent handling, careless assembly, movement of equipment, and other factors, alone or in combination, may cause the convective device to become wholly or partly disconnected from the duct. Users who have experienced therapeutic misadventures through this type of misuse and/or mistake have reported their experiences of thermal injuries to the FDA and the manufacturers of the offending convective treatment systems. Some manufacturers of have responded by warning and training users and affixing labels to the thermal-control/blower units and convective devices. Despite warnings, training, and labeling, however, persons continue to be injured through misuse of warming devices. 
     The American Society for Testing and Materials (ASTM) has recently circulated a draft standard (ASTM F29.19.01) from the Subcommittee for Patient Warming Equipment entitled Standard Specification for Circulating Liquid and Forced Air Patient Temperature Management Devices. The members of the ASTM subcommittee recognized the hazards associated with the practice of free-hosing and developed requirements for equipment to limit skin surface temperatures to 48° C., or manufacturers of thermal-control/blower units to affix a cautionary statement to the distal end of the air supply duct that warns the user against the practice of “free-hosing.” Thus, the ASTM standard explicitly recognizes the importance of air temperature, and tacitly acknowledges the role of airflow, in causing thermal bums. 
     Hosing causes at least four uniquely hazardous conditions to exist: 1) The loss of the resistance from the lack of an convective device leads to a decrease in the residence time of warmed air in the air supply duct. As the warmed air has less time to cool in the air supply duct, it arrives at the distal end of the duct at a higher than normal temperature; 2) The lack of airflow resistance from the absence of the convective device also leads to an increase in the air velocity and quantity of air that is exhausted from the supply duct; The relative increase in air velocity can lead to significantly higher heat transfer rates if the air strikes the skin; 3) The lack of a convective device makes it possible for the high temperature and high velocity air to strike directly the person&#39;s skin over a very small area. In essence, all, or most, of the heat energy intended to be distributed over a large surface area is concentrated onto a very small area; and 4) The lack of a convective device makes it possible for the air supply duct itself to make direct contact with the person&#39;s skin. 
     It is manifest that the hazards of hosing are not intentionally visited on any victim. Nevertheless, it is the case that large caseloads and near-crisis conditions can distract the attention of those who are in charge of the immediate operation of convective treatment systems. In such circumstances, the practitioner may be unaware of the development of conditions that pose a hazard of bums, or may be forgetful of known conditions that require close and constant attention. Accordingly, significant benefits would be realized by safety provisions that operate to reduce the risk of harm that can arise during the operation of convective treatment systems. Especially desirable are measures that would warn the practitioner when the supply duct is separated from the convective device while the air duct is still being supplied with pressurized, warmed air. 
     The assignee of this application has designed safety provisions that reduce the risk of burns by modulating the operation of a blower in response to changes in the integrity of the connection between the air duct and the convective device. These provisions are set out in U.S. Pat. No. 6,126,681, a continuation-in-part thereof, U.S. patent application Ser. No. 09/546,078, a divisional thereof U.S. patent application Ser. No. 10/024,387 and a continuation-in-part U.S. patent application Ser. No. 10/131,068, all of which are incorporated herein by this reference. 
     Nevertheless, there is an immediate need for additional measures in convective treatment technology to quickly, effectively, and automatically warn of a potentially unsafe condition in which the distal end of the air supply duct is not connected, or not connected completely, to a convective device while pressurized air is still flowing through the duct. 
     BRIEF SUMMARY OF INVENTION 
     It is an object of this invention to automatically sound a warning of or otherwise audibly indicate a condition where an air supply duct that is still conducting pressurized air is not connected to a convective device. 
     A further object of this invention is provision of a wind-actuated instrument for sounding the warning which does not interfere with the normal operation of a convective device when properly attached to the air supply duct. 
     The invention is based on the critical realization that there exists an interface in a convective treatment system where measures can be implemented to sound a warning or provide an audible indication when the air supply duct is disconnected, uncoupled, or detached from the convective device under the condition that pressurized air is still flowing through the duct. The interface is where the connection, coupling, or attachment of the air supply duct with the convective device is made. At this interface, an interface device with a wind-actuated instrument is provided that sounds a warning, generates an audible indication or provides an alarm when the air supply duct is disconnected, uncoupled, or detached from the convective device and pressurized air is still flowing through the air supply duct. In addition, the interface device may also reduce, restrict or stop the flow of air through the air supply duct when the end is disconnected, uncoupled, or detached from the convective device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1A and 1B illustrate a convective treatment system in which the invention may be deployed. FIG. 1B is a magnified partial perspective view of a portion of a convective device where an inlet port is located, with an end of an air hose positioned to received in the inlet port; 
     FIGS. 2A through 2D illustrate one embodiment of the invention; 
     FIG. 3 is an exploded view of the interface device according to another embodiment of the invention. 
     FIG. 4 illustrates the interface device of FIG. 3 in the closed position; 
     FIG. 5 illustrates the interface device of FIG. 3 prior to attachment to an inlet port; 
     FIG. 6 illustrates the interface device of FIG. 3 attached to the inlet port; 
     FIG. 7 illustrates the interface device of FIG. 3 when disconnected from the inlet port (closed position) with air is flowing, sounding the audible alarm; 
     FIG. 8 is a sectional view of FIG. 7; 
     FIG. 9 illustrates the interface device of FIG. 3 when connected to the inlet port (open position) with air is flowing; and 
     FIG. 10 is a sectional view of FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In this description, a convective warming system will be described, together with certain elements of such a system. The elements will be denominated by terms that are selected for syntactic convenience and utility in suggesting a structure or a function. The terms are not selected, nor are they intended, to constrain or limit the range of structural and functional equivalents to which the elements, alone or in combination, are entitled. 
     In this regard, the terms “blower” and “convective device” are defined above. The term “air supply duct” is used in the background to denote a tubular passage through which air is pressurized by the blower and conducted from the blower to a convective device in a convective treatment system. Hereinafter, the term “air hose” will be used in place of “air supply duct” in order to convey the sense of a flexible tubular passage. The air hose has two ends, one for connection to the blower, the other for connection to the convective device. For convenience of this description, and for no other purpose, the end that is to be connected to the convective device may also be called a “distal” end. In the context of the invention, it is presumed that the air hose conducts pressurized air that is warmed; indeed the air may even be called “hot”. This is intended to convey the sense that the temperature of the air has the potential to be raised to a level in a range, and that that level or any other level in the range results in a nozzle temperature that poses a risk of harm to a person if blown directly onto the person from the nozzle of the air hose, with the convective device removed. 
     The term “interface device” is also used in this description. In this application, an interface device is a device, an apparatus, an appliance, or any equivalent structure or means, that is located near where the connection, coupling, or attachment of the air hose with the convective device is made. The interface device includes a wind-actuated instrument that sounds an audible alarm indicating that the air hose is no longer attached to the inlet port and that pressurized air is still flowing through the air hose. Optionally, the interface device may also be provided with other means to wholly or partly close the distal end of an air hose in order to reduce, restrict, attenuate, or even stop the flow of air out of the air hose. The interface device can perform these functions without a nozzle being mounted to the end of the air hose. Alternatively, the interface device may be received on a nozzle at the end, integrated into the structure of a nozzle at the end, or may itself act also as a nozzle at the end. 
     The term “wind-actuated instrument” is used in this description. In this application, a wind-actuated instrument emits an audible output when activated by a flow of air. While the term whistle is used in the description, it is intended not to be limiting. Many other wind-actuated devices may be used in the practice of this invention including vibrating or oscillating reeds, membranes, objects (like a ball in a whistle), and valves, and shaped passages (like the aperture on the spout of a tea kettle), and other equivalent instruments. 
     The term “inlet port” is used in this description as well. Convective devices employ a variety of inlet port structures. In this application, an inlet port is any component of a convective device configured to allow for the ingress of pressurized air. Inlet ports may come in the form of sleeves, sheets flexible of material, and rigid structure with defined openings. 
     Refer to FIGS. 1A and 1B in which a convective treatment system  10  is illustrated. The elements of the system  10  include a blower  12  that aspirates air from the ambient environment, raises its temperature to a desired level, pressurizes the air above ambient pressure, and discharges the heated, pressurized air at an exhaust port  14 . An air hose  16 , with two ends,  18  and  20 , is provided. The end  18  is connected to the exhaust port  14  and the air hose  16  conducts the heated, pressurized air to the end  20 . The end  20  is connected, coupled, or joined to the inlet port  22  of a convective device  24 . In this regard, the equivalent action from the point of view of the convective device  24  is that the end  20  is received in, or by, or near the inlet port  22 . When the end  20  and the inlet port  22  are thus brought together, the heated, pressurized air is conducted through or out of the end  20  into the convective device  24 . 
     A representative convective device with an inlet port is described in in the assignee&#39;s U.S. Pat. No. 6,309,408, which is incorporated by this reference. The convective device  24  and its associated inlet port  22  may be understood with reference to the &#39;408 patent, in which an inflatable device has an opening around which is mounted a relatively stiff sheet of cardboard material. The sheet of cardboard material has an opening that is aligned with the opening in the inflatable device. The sheet provides structure to receive, retain and support the end or nozzle of an air hose in an inlet port. This arrangement, shown in FIGS. 15 and 16 of the &#39;408 patent, is instructive in understanding the embodiments which are described below. 
     Completing the description of the system  10 , with reference to the &#39;408 patent as an instructive example, heated, pressurized air is conducted into the convective device  24  which conveys the air from the inlet port  22  into its interior, imposing a heat loss that reduces the temperature level of the air, and extravises the heated, pressurized air through one or more surfaces of the convective device  24 . The system  10  thus delivers thermally-regulated air to the convective device  24 , and the device distributes the thermally-regulated air around a person or a specific body area of the person. 
     In order to afford protection from injury that could result should the end  20  become separated from the inlet port  22 , either by accident or by intentional action, the incorporated applications describe embodiments of an interface device that controls the interface between the inlet port  22  and the end  20 . When the end  20  is connected, coupled, or joined to the inlet port  22 , the interface device operates to allow pressurized, thermally-regulated air to flow through the end  20  into the convective device  24 . In this invention, when the end  20  is disconnected, uncoupled, or separated from the inlet port  22  while pressurized air is still flowing, the interface device sounds an audible alarm or warning of this condition. Optionally, in addition to the audible alarm, the interface device may also operate to wholly or partly close the end  20  of the air hose  16  in order to reduce, restrict, attenuate, or even stop the flow of air through the end  20  when disconnected, uncoupled, or separated from the inlet port  22 . A representative example of an interface device that wholly or partly closes the end in order to reduce, restrict, attenuate, or even stop the flow of air through the end when disconnected, uncoupled, or separated from the inlet port is described in detail in the assignee&#39;s U.S. patent application Ser. No. 10/131,068, which is incorporated by this reference. Some or all of the interface devices disclosed in U.S. patent application Ser. No. 10/131,068 could accommodate the audible indicator or alarm. Refer now to the remaining drawings, which illustrate various embodiments of the interface device. 
     In FIGS. 2A through 2D, an interface device that exemplifies this invention is illustrated. The end  20  of the air hose  16  terminates with an interface device  30 . In this embodiment, the interface device  30  includes a wind-actuated instrument  32 , such as a whistle or equivalent element, to sound an audible alarm. Referring to FIGS. 2A and 2B, when the end  20  is not connected or is separated from the inlet port  22  while pressurized air  34  is flowing, the wind-actuated instrument  32  is operated by the pressurized air to sound, generate, provide, or otherwise issue an audible alarm or warning  36 . The audible alarm  36  indicating to the user that the air hose  16  is not connected or has disconnected from the inlet port  22 . Referring now to FIGS. 2C and 2D, the end  20  is connected to the inlet port  22 . Assuming for illustration that the inlet port  22  discussed above includes an inlet port structure such as that disclosed in U.S. Pat. No. 6,309,408, it would include a sheet  28  of flexible, somewhat deformable material (such as cardboard) in which a port opening  26  is provided. In this case, the slits about the perimeter of the inlet port  26  form a plurality of fingers  38 . The fingers  38  allow the port to accommodate the end or nozzle of the inflation hose which is slightly larger in outside diameter than the inner diameter of the port. As the end  20  is inserted into the inlet port  26 , the fingers  38  spread apart to allow the insertion of the interface device  30 . The fingers  38  are long enough to cover the wind-actuated instrument  32  when the end  20  is coupled to the inlet port  26 . When coupled correctly, the fingers  38  block the flow of pressurized air through the wind-actuated instrument  32 . The interface device  30  may be a separate component or may be integral with the end  20  of the air hose. In addition, the wind-actuated instrument  32  may be a separate component, may be integral with the interface device  30  or may be integral in the end  20  of the air hose. It is contemplated that the inlet port may instead be a sleeve obviating the need for fingers to occlude the flow of air as the sleeve can be drawn up to cover the wind actuated instrument. 
     FIG. 3 shows another embodiment of the interface device with a wind-actuated instrument that may also include a shutter. In this case, when the end  20  and the inlet port  22  are brought together the shutter opens (or, is opened) to permit pressurized air to flow out of the end  20  into the convective device. This may be considered the safe position. Likewise, when the end  20  is separated from the inlet port  22 , the audible alarm is generated while the shutter closes (or, is closed), to reduce, restrict, or prevent the flow of air out of the end  20 . This may be considered the alarm position. 
     In the example set forth here to illustrate the invention, the interface device  100  includes an end piece  102  comprising a tubular section  104  and a cylinder section  106 , the tubular section  104  bisecting the cylinder section  106  at 90 degrees, the tubular section  104  in fluid communication with the cylinder section  106 . A generally triangular opening  108  is disposed generally in the center of the cylinder section  106  diametrically opposite the tubular section  104 . An elongate slot  110  opens into the periphery of the opening  108  and an arcuate lip  112  is provided adjacent the periphery of the opening  108 , opposite the slot  110 . The elongated slot  110  has a closed end  110   a . A wind-actuated instrument may be mounted, seated or received in the interface device  100 ; it may be attached, connected, or coupled to the interface device; or, it may be formed integrally therewith. In the illustrative example being described, the instrument is embodied as a whistle  114  that is provided in the cylinder section  106  near the opening  108 . The end piece  102  is preferably a unitary element formed, possibly, by molding a durable plastic. The end piece  102  is assembled to an annular collar  26  on the end  20 , for example by threaded screws that extend through the tubular section  104  into the annular collar  26 , although other modes of attachment are possible. A first end cap  116  is designed to sealingly attach to a first end  118  of the cylinder section  106  and a second end cap  120  is designed to sealingly attach to a second end  122  of the cylinder section  106 . When assembled in this manner, the opening  108  and whistle  114  permit pressurized air to flow out of the end  20 . 
     The interface device  100  further includes a moveable cylindrical shutter  124  having a generally cylindrical shape that corresponds to the cylindrical shape of the cylindrical section  106 . The external diameter of the shutter  124  is less that the internal diameter of the cylindrical section  106  so that when the shutter  124  is received in the cylindrical section  106  it can rotate or be rotated in the cylindrical section about an axis it shares with the cylindrical section. The length of the shutter  124  is less than the length of the cylindrical section  106  so that end caps  116  and  120  will not interfere with the shutter rotation. The shutter  124  may be formed of a hard plastic. The shutter  124  includes an inlet opening  126 , a triangular outlet opening  128  and a whistle opening  130 . The opening  128  is generally the same size and shape of opening  108 . An arcuate lip  132  is provided adjacent to the periphery of the opening  128  and a trunnion  134  is mounted on and projecting outwardly from the shutter  124 . Both the arcuate lip  132  and the trunnion  134  are sized to fit in and extend through the elongate slot  110 . Internal to the shutter  124  is an air diverter  135  that either diverts air to the whistle  114  or blocks that air from the whistle  114 , depending on the position of the shutter  124  within the end piece  102 . When air is diverted to the whistle  114 , the shutter  124  is considered in the alarm position and the whistle  114  makes an audible indication or alarm. When air is blocked from the whistle  114 , the shutter  124  is considered in the open or safe position. 
     FIG. 4 shows the interface device  100  in the closed position. The shutter  124  is rotated by moving trunnion  134  toward the closed end  110   a  of the elongate slot  110 . In this position, opening  128  of the shutter  124  is not completely aligned with opening  108  of the end piece  102  some air will be divert by the air diverter  135  to the whistle  114 . This can also be seen in FIGS. 7 and 8, which will be described below. FIG. 5 shows the interface device  100  prior to being attached to the inlet port  22 . The shutter  124  is rotated toward an open position by moving trunnion  134  away from the closed end  110   a  of the elongated slot  110  until the arcuate lips  112  and  132  fit in the opening  26  of the inlet port  22 . Once the arcuate lips  112  and  132  are inserted through the opening  26 , the shutter  124  is then rotated in the opposite direction by moving trunnion  134  toward the closed end  110   a  of the elongate slot  110  until the arcuate lips  112  and  132  engage the edges  26   a  and  26   b  of the inlet port  22 . This will lock the interface device  100  to the inlet port  22 , as shown in FIG.  6 . The interface device  100  is then in the open position with the opening  128  of the shutter  124  aligned with opening  108  and no air is diverted to the whistle  114 . This can also be seen in FIGS. 9 and 10, which will be described below. 
     As thus far described, the interface device  100  can be operated manually by moving the trunnion  134  in the elongate slot  110 . The self-actuated operation of the interface device  100  can be understood with reference to FIG. 3. A spring  136  is shown having a first end  138  and a second end  140 . A tab  142  is on one end of the shutter  124  that engages spring first end  138 . One such engagement is a hole  144 . The second end  140  of the spring  136  is placed in a hole  146  in an end cap  120 . When in place, the spring  136  acts between the shutter  124  and the cylindrical section  106  by urging the shutter  124  to closed position, where the trunnion  134  is rotated toward the closed end  110   a . When the trunnion  134  contacts the closed end  110   a , this stops the shutter  124  at the position where the opening  128  is not completely aligned with opening  108  so that any air flow would be reduced, attenuated, restricted or blocked and the air diverter  135  diverts some air to the whistle  114 . Manual engagement of the trunnion  134  with a force in the opposite direction moves the trunnion  134  away from the closed end  110   a  and rotates the shutter  124  to a position where the alignment of the openings provide at least one aperture through the interface device  100  that is in fluid communication with end  20  and permits air flow from the end  20  though the interface device  100 . 
     A self-actuating operation of the interface device  100  can now be described. To bring the end  20  together with the inlet port  22 , the shutter  124  is rotated by pressure applied against the trunnion  134 . With the shutter  124  held in this position, the interface device  100  is brought against the inlet port  22 , with the arcuate lips  112  and  132  extending through the port opening  26 . When the pressure is taken off the trunnion  134 , a force by the spring  136  urges the arcuate lips  112  and  132  into engagement against the periphery  26   a  and  26   b  of the port opening  26 . This keeps the shutter  124  in the position at which pressurized air flows out of the end  20 , through the inlet port  22  and no air is diverted to the whistle  114 . The end  20  is separated from the inlet port  22  by sliding the trunnion  134  away from end  110   a . This disengages the arcuate lips  112  and  132  from the periphery  26   a  and  26   b  of the port opening  26 . Once separated, the spring  136  urges the shutter  124  to be returned to the closed position to reduce, restrict, or prevent the flow of air out of the end  20 , and the air diverter  135  diverts air to the whistle  114  to produce an audible indication or alarm that the end  20  is separated from the inlet port  22 . 
     The operation of the interface device  100  with respect to the interface between the end  20  of the air hose  16  and the inlet port  22  can be understood with reference to FIGS. 5,  6 ,  9  and  10 . Assuming again for illustration that the inlet port  22  includes an inlet port structure such as that disclosed in U.S. Pat. No. 6,309,408, it would include a sheet  28  of flexible, somewhat deformable material (such as cardboard) in which a port opening  26  is provided. It should be understood that the sheet  28  and the opening  26  may be many different shapes, for example, circular shape, as shown in FIG. 1B, FIGS. 2A-2D, or triangular shape, as shown in FIG.  4 . The interface device  100  is mounted to the end  20  of the air hose  16 , as described above. 
     FIGS. 7 and 8 show the interface device  100  in the closed position, the openings in the interface device are not aligned, the flow of air is reduced or restricted and the air diverter  135  diverts some air toward the whistle  114 . Air  148  flows in the air hose  16  into the interface device  100  located on end  20 . In this closed position, the air diverter  135  in the interface device  100  separates the flowing air  148  into two components. A first air portion  150  is diverted to the whistle  114  and an audible alarm or whistle  115  is sounded, indicating improper operation of the equipment. A second air portion  152  continues through the interface device  100 , exiting through the non-aligned openings. In other embodiments, this second air portion  152  may be prevented or blocked from flowing out of the end  20 . 
     FIGS. 9 and 10 show the interface device  100  in the open position. The end  20  is joined with the inlet port  22  by rotating the shutter  124  and attaching the interface device  100  to the inlet port  22 , as described above. In the open position, the openings in the interface device  100  and inlet port  22  are aligned. Air  148  flows in the air hose  16  into the interface device  100  located on end  20 . In this position, the air diverter  135  blocks from flowing to the whistle  115 , so no audible indication is sounded. The air  148  continues through the interface device  100  and the inlet port  22  into the convective device  24 . In this embodiment, the alignment of the openings provides a path through the interface device  100  that is in fluid communication with the end  20  an permits air to flow from the end  20 , through the interface device  100 , at the relatively high rate.