Patent Publication Number: US-2011060300-A1

Title: Aspiration system for removing liquid discharged by the body, and liquid sensor therefor

Description:
FIELD OF THE INVENTION 
     The present invention relates to an aspiration system for removing liquids, discharged by the human body. The invention is especially suitable for removing urine, but the invention is not limited only to urine, and may be used for other body fluids and secretions. 
     BACKGROUND TO THE INVENTION 
     U.S. Pat. Nos. 5,002,541, 4,747,166 and 4,631061 describe human urine aspiration systems. The urine removal systems include an electric pump for applying suction to a urinal. The urinal includes a liquid sensor for automatically activating the pump when the presence of liquid urine is detected. The three patents all describe liquid sensors in the form of electrodes forming a normally open circuit that is closed by conduction through liquid, when the sensor is contacted by liquid. The last patent also describes an alternative liquid sensor in the form of an optical sensor. 
     The use of such an automatic aspiration system for removing urine has the potential to provide significant advantages compared to conventional urine management techniques. For example, the system can avoid the need for a patient to wear diapers to collect urine, with the consequent burden on hospital staff or other caregivers to frequently check and change the diaper. The system can also avoid the need for an in-dwelling urinary catheter for draining urine. There is a significant rate of nosocomial urinary tract infections contracted by patients who are catheterized for substantial lengths of time. Such infections are very serious because they can be fatal and, at the very least, lead to increased recovery times in the hospital and additional cost and burden for hospital staff and caregivers. 
     It would be desirable to improve on prior art designs of aspirated liquid removal systems, in order to satisfy commercial need and improve customer acceptance. In devising the present invention, the inventors appreciated that one aspect that would benefit improvement is in the speed of response of the system to aspirate urine. The present invention has been devised bearing these issues in mind. 
     SUMMARY OF THE INVENTION 
     In devising the present invention, it has been appreciated that it would be desirable to improve the liquid sensing techniques of the prior art. Previous liquid sensing techniques may be quite insensitive, by having to rely on a sufficient quantity of liquid to effectively short circuit two electrodes, or by having to provide electrodes over a large area of a urinal to provide sufficient conduction sensitivity. 
     In one aspect, the invention provides a liquid sensor for an aspiration system for removing body liquids discharged by the human body, the liquid sensor being a temperature sensor. 
     The use of a temperature sensor can provide a reliable and quick indication of body liquid exiting the body, without requiring the sensor to be dispersed over a large area. Liquid, such as urine, exits the body at a temperature of about 37° C., which is notably higher than ambient room temperature (typically about 23° C.), and also higher than the ambient temperature of a sensor positioned close to the human skin (typically about 32° C.). 
     The presence of liquid is detected by detecting (i) a rapid change in temperature and/or (ii) a temperature rise above a threshold, such as above 36° C. 
     In another aspect, the invention provides a liquid sensor for an aspiration system for removing body liquids discharged by the human body, the liquid sensor comprising a resistance bridge circuit generating a bridge output that is responsive to contact of one of more bridge elements with liquid. The bridge circuit comprises at least one element whose resistance varies when contacted by liquid. The element comprises first and second spaced apart electrodes. 
     The liquid sensor may further comprise a monitoring circuit for monitoring the bridge output. 
     The use of a bridge circuit provides a highly sensitive liquid detector, by enabling a moderate change in resistance to be easily detected. This provides a faster response than, for example, relying on a sufficient quantity of liquid to completely short circuit two electrodes. 
     Also, in devising the present invention in another aspect, the inventors appreciated that it would be desirable to improve the manner of application of aspiration suction once liquid has been detected. The techniques of the above prior art inherently involve delay while the suction pump gets up to speed. It may be possible to employ a more powerful pump, but this would add significantly to the cost, weight and power consumption of the apparatus. 
     In accordance with this aspect, the invention provides an aspiration system for removing body liquids discharged by the human body, comprising: a vacuum chamber; a pump for charging the vacuum chamber with a vacuum; a body interface device (e.g., urinal) through which liquid is collected and having a liquid sensor; an electronically controlled valve for controlling the application of vacuum from the chamber to the body interface device in order to suck liquid away from the body interface device; and a control circuit for controlling the valve. 
     With such an arrangement, a vacuum can be applied more quickly from the pre-charged vacuum chamber, than waiting for a pump to start-up, and achieve a normal pumping capacity. This facilitates rapid response and removal of a large quantity of liquid from the body interface device, and thereby reduce the likelihood of spill or saturation of the body interface device. The use of a vacuum chamber also provides a greater instantaneous suction than the volumetric capacity of the pump. 
     The valve may be a variable aperture valve, for regulating variably the amount of suction according to the aperture size. Alternatively, the valve may be an open/close valve. The control circuit may be configured to regulate the effective aperture of an open/close valve by generating a pulsed control signal. The effective aperture is defined by the ratio of on-time to off-time of the pulsed control signal. Alternatively, the valve may be a change-over valve for selecting between two or more different suction paths from the vacuum chamber, having different resistances. The paths may include a relatively unrestricted path for applying large suction from the vacuum chamber, and a relatively restricted path for applying a smaller suction. 
     In another general aspect, the invention provides an aspiration system for removing body liquid (e.g., urine or a secretion) discharged by the human body. The aspiration system comprises a body interface device with a liquid sensor, and an aspiration unit coupled to the body interface device. The liquid sensor comprises a temperature sensor or a resistance bridge. The aspiration unit includes: a vacuum chamber; a pump for pre-charging the vacuum chamber with a vacuum; a valve coupled between the vacuum chamber and the body interface device; and a control circuit for controlling the valve to apply aspiration suction from the vacuum chamber to the body interface device in response to detection of body liquid at the liquid sensor. 
     As used throughout this specification, the term “vacuum” refers to any pressure below ambient atmospheric pressure. In one form, the term “vacuum” refers to a pressure below 101 kPa. The reference to “charging” a vacuum means removing air to generate a vacuum. Also, as used herein the term “urinal” refers to any device of any form or shape configured for receiving urine directly from a human body orifice (such as a cup-shaped female urinal, a male condom urinal, or a urostomy body fitment). 
     Although features believed to be of significance have been highlighted above and/or in the claims, the Applicants may seek claims protection for any novel feature or idea disclosed herein and/or illustrated in the drawings, whether or not emphasis has been placed thereon. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic block diagram of a first embodiment of liquid removal system. 
         FIG. 2  is a schematic cut-away view of the urinal of the liquid removal system. 
         FIG. 3  is a schematic circuit diagram of a resistance bridge. 
         FIG. 4  is a schematic block diagram of a second embodiment of liquid removal system. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The same reference numerals are used to depict the same or equivalent features in each of the embodiments described below. 
     Referring to  FIG. 1 , an aspiration system  12  for removing body liquid discharged by the human body generally comprises an aspiration unit  12   a  and a body interface device  12   b  coupled to the aspiration unit  12   a  by means of a flexible conduit  12   c . The flexible conduit  12   c  may be regarded as part of the aspiration unit  12   a  and/or part of the body interface device  12   b . The body interface device  12   b  is configured for fitting to the body at, or around, the site of discharge of the body liquid desired to be collected. In the example of urine removal, the body interface device  12   b  is configured to fit at the genital region of a male or female wearer, or a surgical urostomy. For females, the body interface device  12   b  is in the form of a snug-fitting urinal (as illustrated herein). For males, the body interface device  12   b  is in the form of a condom (not illustrated). For urostomates, the body interface device  12   b  is in the form of a stoma fitment (not illustrated). The present embodiment is especially suitable for removing urine, since urine removal is most challenging in terms of the volume of the liquid to be removed and the speed of liquid discharge. The speed of response of the apparatus to detect and remove the liquid is a significant factor in the ability of the apparatus to manage a urine discharge. 
     The aspiration unit  12   a  comprises a vacuum chamber  3 , a pump  2  for removing air from the vacuum chamber  3  to charge the vacuum chamber  3  with a vacuum, an electronically controlled control valve  9  for controlling the application of vacuum from the vacuum chamber  3  to the body interface device  12   b , and a control circuit  10  for controlling the valve  9 . The pressure within the vacuum chamber  3  is monitored by a pressure sensor switch  1 , which in turn controls the application of electrical power from a power supply  4  (via a master device on/off switch  5 ) to the pump  2 . When the pressure is above a predetermined threshold (such as 87.6 kPa), the pressure sensor switch  1  closes to operate the pump  2  in order to pump out air, and charge the vacuum chamber  3  with a vacuum. Once the pressure drops below the threshold, the pressure sensor switch  1  opens to stop the pump  2 . The pressure sensor switch  1  continues to monitor the pressure in the vacuum chamber  3 , and to operate the pump  2  as necessary to maintain a low pressure vacuum within the vacuum chamber  3 . The pressure sensor switch  1  may optionally include hysteresis in the switching threshold to avoid the pump  2  being activated continuously in a short intermittent manner. Additionally or alternatively, the pump  2  may be controlled to continue pumping for predetermined time duration after the switching threshold has been achieved. 
     In the present embodiment, the control valve  9  is a 3-port solenoid operated changeover valve that couples the body interface device  12   b  to the vacuum chamber  3  via one of two parallel paths  5   a ,  5   b . Path  5   a  is a substantially unrestricted high-vacuum path for applying full suction to the body interface device  12   b , in order to remove liquid when detected. Path  5   b  is a relatively restricted, low-vacuum path (more restricted than the high-vacuum path  5   a ), for applying moderate suction (or no suction) to the body interface device  12   b  in a quiescent state of the apparatus. In one form, it may be desirable to cut all suction; in another form, it may be desirable to maintain a moderate suction to keep the body interface device dry, to remove small drips of liquid or other contaminants, and/or to cause the body interface device  12   b  to gently hug the skin. A needle valve  8  in path  5   b  permits the low-vacuum level to be regulated to a desired amount, or for suction to be cut-off by closing the needle valve  8 . In the present embodiment, as a failsafe, the control valve  9  is configured to select the low-vacuum path  5   b  when no electrical power is applied to the control valve  9  and the solenoid is deactivated, and to select the high vacuum path  5   a  only when electrical power is applied to the control valve  9  to activate the solenoid. Although only two paths  5   a ,  5   b  are illustrated, it will be appreciated that additional parallel paths of different flow resistance may be provided, and between which the control valve  9  selects a path, in order to increase the finesse of control of suction. 
     The control circuit  10  receives an input from a liquid sensor  13  located in the body interface device  12   b . The electrical signal from the liquid sensor  13  is transmitted to the control circuit  10  by means of electrical cable  33 . In one form, the liquid sensor  13  comprises a temperature sensor for measuring the temperature at the body interface device  12   b . When body liquid such as relatively warm urine or body secretion is discharged into the body interface device  12   b , the temperature increases. The presence of body liquid is detected by a temperature sensor sensing a temperature value exceeding a preset threshold value between 30° C. and 42° C. and/or a rate of increase in temperature of at least 1° C. within two seconds. The use of a temperature sensor can provide a reliable and rapid indication of the presence of discharged body liquid. 
     In another form, the liquid sensor  13  comprises a resistance bridge circuit, such as that illustrated in  FIG. 3 , and comprising at least one element A that is responsive to liquid. The element A may have a resistance responsive to the presence of liquid. The element A may comprise two spaced apart terminals. The use of a resistance bridge circuit can provide a liquid sensor that is sensitive to variation in electrical resistance even in the presence of a small quantity of liquid. 
     Alternatively, the liquid sensor may be a combination of both of the above, comprising a temperature sensor in a resistance bridge circuit. 
     In use, the control circuit  10  monitors the output from the liquid sensor  13  to detect presence of body liquid entering the body interface device  12   b . When liquid is detected, the control circuit  10  activates the control valve  9  to select the high vacuum path  5   a  for applying full suction from the vacuum chamber  3  to the body interface device  12   b . The liquid is sucked out of the body interface device  12   b , via the flexible conduit  12   c , the control valve  9  and the high-vacuum path  5   a  to the vacuum chamber  3 . At the vacuum chamber  3 , the liquid drops down under gravity into a collection chamber  7 . The collection chamber  7  may optionally be accommodated in the aspiration unit  12   a , or it may be coupled to an external fixture of the aspiration unit  12   a . In either case, the collection chamber  7  may be removably coupled by a suitable connector  6 , for cleaning, emptying or replacement. Preferably the connector  6  is a quick disconnect connector. A connector valve  6   a  prevents escape of vacuum in the vacuum chamber  3  when collection chamber  7  is removed. The connector valve  6   a  may be operated manually, or automatically when the connector  6  is disconnected. The collection chamber  7  may optionally include a drain output  7   a  with a drain valve  7   b  that may be toggled between open and closed conditions. The collection chamber  7  may also optionally be transparent with graduations  7   c , or include a graduated window, so that the amount of collected liquid can be visually inspected and measured. 
     The use of the pre-charged vacuum chamber  3  enables a high vacuum to be applied to the body interface device  12   b  rapidly, in order to quickly remove even a large quantity of liquid, without any delays associated with a vacuum pump starting or reaching full pump speed. Also, liquid can be sucked away from the body interface device at a greater instantaneous volume capacity than the volumetric capacity of the pump. Instead, the pump  2  is used to pre-charge the vacuum chamber  3  with a vacuum, and to maintain or re-charge the vacuum in the vacuum chamber  3  over time. The pump  2  may therefore be relatively small and/or lightweight as desired. 
     Once the majority of the liquid has been sucked away, the liquid sensor  13  will generate a non-liquid output signal. For example, in the case of a temperature sensor, the temperature will decrease towards ambient temperature. In the case of a resistance bridge, the resistance will return to its pre-liquid value. In response, the control circuit  10  deactivates the control valve  9  to apply the low vacuum (or no suction, if desired) for quiescent operation. The control circuit  10  may either deactivate the control valve  9  immediately upon the absence of liquid being detected, or after a predetermined time delay subsequent to the absence of liquid being detected. 
     A manual switch  11  is also provided, coupled to the control unit  10 , for manually commanding high vacuum suction from the vacuum chamber  3  when desired. The manual switch  11  provides additional versatility for the patient or caregiver, as well as a back-up failsafe control. The high vacuum suction may be applied either for a preset time (using a timer circuit in the control circuit  10 ), or while the manual switch  11  is continued to be depressed (in the case of a spring-loaded press-to-make switch) or until the manual switch  11  is toggled or operated again to command a stop of the high vacuum suction. 
     Referring to the general view of  FIG. 1 , and the more detailed view of  FIG. 2 , the body interface device  12   b  is removably attachable and re-attachable to the body to facilitate cleaning. A cover component  15  of the body interface device  12   b  may have a flexible boot or skirt  14  located near the body attachment  14   a  for comfort and to provide a seal to the body. The boot  14  may impart a hugging action when vacuum is applied. The body attachment  14   a  may adhesively engage the skin  16  and the boot  14 . The cover component  15  comprises an outer shell made of soft semi-rigid and/or flexible material. Two chambers are configured within the cover  15 , and are divided by a chamber divider  30 . In a first or inner chamber  15   a , at a mouth area where the cover component  15  is most proximal to the body is an inner open cell foam  24  which covers the entire inside area of the cover  15  and is the primary element of the first, inner chamber  15   a . A plurality of small air inlets  27  is provided around the periphery and underneath the inner open cell foam  24 . 
     The chamber divider  30  is provided directly underneath the inner open cell foam  24 , and is made of a material more resistant to fluid penetration than the inner open cell foam  24 . The chamber divider  30  is attached in such a way as to provide a seal to the outer shell  29 . The chamber divider  30  has a center slit opening  28  through which the removing fluid will pass. The air inlets  27  are positioned so as to provide an air flow from the inlets  27  across the surface of the chamber divider  30  and into the center slit opening  28 , and thereby direct fluid toward the center slit opening  28 . As an alternative to a single center slit opening  28 , the chamber divider  30  could comprise plural apertures of holes over its surface. 
     Below the chamber divider  30  is an outer open cell foam  23  which supports and is trapped by the chamber divider  30  and the outer shell  29 . The liquid sensor  13  (temperature sensor or resistance bridge) is positioned on top of the outer open cell foam  23 , so as to be in the middle of the center slit opening  28  and in direct line with e.g., the urethra (in a female urine removal system). The connecting conduit  31  is attached to the outer shell  29  and/or the outer open cell foam  23 , and a hole in the outer shell  29  where the connecting conduit  31  is located is in line with the urethra and liquid sensor  13 , and provides the pathway for the liquid to be sucked away. The electrical cable  33  from the liquid sensor  13  passes through the outer open cell foam  23 , through the outer shell  29  and accompanies the connecting conduit  31  towards the aspiration unit  12   a . The connecting conduit  31  and the electrical cable  33  include a quick disconnect  25  to allow (i) the wearer to temporarily disconnect from the aspiration unit  12   a  without removing the body interface device  12   b  from the body, and/or (ii) replacement of the body interface device  12   b  or its cover component  15 . The quick disconnect  25  may comprise separate connectors for the suction connecting conduit  31  and the electrical cable  33 , or the quick disconnect  25  may integrate the connectors for both in a common connector housing. 
     In another embodiment of the body interface device  12   b , the quick disconnect  25  may have one portion located near the proximal end of the connecting conduit  31  where the leading end of the connecting conduit  31  is inserted into an opening in the cover component  15  and into the outer chamber  15   b . The liquid sensor  13  may be mounted on the outer surface of the connecting conduit  31 , and the quick disconnect  25  configured, such that the liquid sensor  13  with the connecting conduit  31  passes through another portion of the quick disconnect  25  specific to the body interface device  12   b  and aligns with the center slit opening  28  so as to be in line with the urine stream. The quick disconnect  25  has a feature that provides this alignment. The connecting conduit  31  has a plurality of openings near its end such that the openings are within the outer chamber  15   b  when connected to the body interface device  12   b . the open end of the connecting conduit  31  may have a restriction so as to effect the vacuum over the other openings near the end of the connecting conduit  31 . Also, the distal end of the connecting conduit  31  and the electrical cable  33  may be able to be disconnected from the aspiration unit  12   a  (not shown). This embodiment enables the connecting conduit  31  and the liquid sensor  13  to be completely removed from the body interface device  12   b  and connected to a new body interface device  12   b  or other interface used in the collection of liquid discharged from the body. Further, the connecting conduit  31  with the liquid sensor  13  may be replaceable, allowing the aspiration unit  12   a  to be reused with new connecting conduits and sensors. 
     When urination or liquid secretion occurs, the liquid passes through the inner open cell foam  24  and contacts the liquid sensor  13 . The control circuit  10  operates the control valve  9  to apply a high vacuum, as described earlier. The outer chamber consisting of the outer open cell foam  23  is de-pressurized by the applied high vacuum pulling through the center slit opening  28 . Atmospheric air is pulled through the air inlets  27  across the top surface of the chamber divider  30 , in order to channel expelled liquid through the center slit opening  28  into the outer chamber and connecting conduit  31  and away from the body. 
     The present embodiment is especially suitable for urine removal from the human body, and the illustrated body interface device  12   b  is shaped as a urinal for fitting to the female body. However, it will be appreciated that the body interface device  12   b  could be shaped as a condom for fitting to a male&#39;s penis. It will also be appreciated that the urinal body interface device  12   b  could be configured for connection to a stoma of a urostomate. Other configurations of the body interface device  12   b  may be provided depending on the type of liquid or secretion to be collected from the body. 
       FIG. 4  illustrates a second embodiment of liquid removal system that is similar to the first embodiment. The main difference is that, in the second embodiment a single conduit path  5   c  is provided between the vacuum chamber  3  and the body interface device  12   b . The amount of vacuum applied from the vacuum chamber  3  to the body interface device  12   b , is regulated variably by a control valve  20 , under the control of the control circuit  10 . 
     The control valve  20  may have a variable aperture or orifice. Variable aperture valves include a continuously variable aperture valve, such as a servo position control valve, or a valve having a plurality of predetermined discrete aperture sizes. In either case, the position of the valve member, and the aperture size, are controlled by the control signal from the control circuit  10 . 
     Alternatively, the control valve  20  may be of an on/off type, and the effective aperture controlled by means of a pulse modulated open/close control signal. The effective aperture depends on the mark:space ratio of the control pulses, which defines the relative on (open):off (closed) durations. 
     The control circuit  10  is configured to generate a control signal that controls the control valve  20  to regulate variably the vacuum applied to the body interface device  12   b . The control circuit  10  receives inputs from the liquid sensor  13 , and from a vacuum sensor  18  (which replaces the pressure sensor switch  1  of the first embodiment). The control circuit  10  optionally receives a further input from a fluid flow sensor  20   a . The fluid flow sensor  20   a  measures the flow rate through the conduit  5   c . The fluid flow sensor  20   a  may conveniently be included in the control valve  20 . In addition to controlling the control valve  20 , the control circuit  10  controls the pump  2 . The control circuit  10  may also receive a manual command input from a manual switch  11 , as in the first embodiment. 
     The function of the aspiration system  12   a  is similar to that described for the first embodiment, except that the control circuit  10  oversees the control of the pump  2 , and the control valve  9 , depending on the inputs from the vacuum sensor  18 , the liquid sensor  13  and the fluid flow sensor  20   a . The control circuit  10  controls the control valve  20  to provide high vacuum and low vacuum (or no vacuum) states, by controlling the valve aperture. 
     The control circuit  10  may operate to determine the amount or rate of liquid entering the body interface device  12   b , instead of merely detecting the presence or otherwise, and control the control valve  20  variably to apply a vacuum amount corresponding to the amount of liquid, in order to remove the liquid at a rate based on the rate at which the liquid is discharged from the body. This may be more comfortable for the wearer. 
     Additionally or alternatively, depending on the rate of fluid flow, the control circuit  10  may be configured to activate the pump  2  earlier than normal, in order to preserve a vacuum in the vacuum chamber  3  for as long as possible. 
     The control circuit  10  may include a micro-controller, configured to respond to inputs in a pre-programmed manner, such as by using the input signals to access a pre-programmed information map defining the output control signals to be generated. The control circuit  10  may either judge vacuum level switching, and the liquid detection, in the control circuit  10  based on variable sensor inputs, or the judgment may be implemented in the sensors themselves. The switching thresholds of the sensors may be programmable by the controller. 
     It will be appreciated that the foregoing description is merely illustrative of preferred embodiments of the invention, and that many modifications, improvements and equivalents may be within the scope of the invention as claimed.