Patent Publication Number: US-2020275849-A1

Title: Automatic Air Management System

Description:
RELATED APPLICATIONS 
     This application is a continuation of and claims priority to U.S. patent application Ser. No. 14/734,947, filed Jun. 9, 2015, entitled Automatic Air Management System, which claims benefit of and priority to U.S. Provisional Application Ser. No. 62/009,874 filed Jun. 9, 2014 entitled Automatic Air Management System, both of which are hereby incorporated herein by reference in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     Presently, biologically compatible air-based pressure monitoring catheters are used in a number of medical applications to monitor pressure at various locations within a mammalian body. For example, air-based pressure monitoring catheters may be inserted into the skull of a patient thereby permitting the external monitoring of intra-cranial pressure. 
     Currently, a number of air-based pressure monitoring catheters have been developed. Generally, these air-based pressure monitoring catheters comprise a catheter having an air lumen formed therein which communicates with a bladder positioned at or near its distal end. In addition, the catheter includes a connector located at or near its proximal end which may be connected to an external pressure transducer. During use, the volume of the bladder attached to the catheter changes as pressure varies in accordance with Boyle&#39;s Law (P 1 V 1 =P 2 V 2 ). As a result, the pressure of the gas within the catheter becomes equal to that of the environment surrounding the bladder. The media surrounding the bladder must be capable of movement to accommodate the variations in bladder volume as pressure changes. 
     The use of air-based pressure monitoring catheters in low or negatively pressurized environments has proven problematic. When the proximal connector is open to atmospheric pressure in the process of periodically replacing air lost by diffusion through the bladder, the external pressure extant in the body site monitored on a bladder will expel residual air from the bladder. If the pressure is low or negative, a significant amount of residual air may remain in the bladder. The amount of air injected is intended to be sufficient to keep the bladder in an active state. If this volume is added to the residual air in a bladder that has not been completely collapsed by the environment around it, the sum of the residual air and injected air exceed the intrinsic volume of a fully shaped bladder. Should this happen, a positive pressure is established in the bladder. The bladder is now unable to read pressure below the internal pressure created. 
     Air management systems such as those seen in U.S. Pub. No. 2007/0208270, U.S. Pat. Nos. 6,447,462, 8,876,729, and 8,360,988 which are all herein incorporated by reference, allow a user to adjust the amount of air in a system. For example, these systems allow a user to vent the air passage of the catheter to the open environment, then charge the passage with an amount of air. This allows a proper, known volume of air to be located in the system, thereby allowing the system to accurately calculate pressure within a patient&#39;s body. 
     SUMMARY OF THE INVENTION 
     One embodiment is generally directed to a powered or automatic air management system for measuring pressure from an air pressure catheter located within a patient. While prior art air management systems, such as those in U.S. Pat. No. 8,360,988, require a user to manually charge the pressure system with a known volume of air (i.e., by moving a piston by hand), the present embodiment includes powered pumps to automatically adjust the air volume to a desired level. Additionally, while prior systems include the system&#39;s pressure transducer, manual pumps, and other components in a single enclosure, the present embodiment includes a pressure transducer assembly that is located at the bed of the patient and a separate pump assembly that is fixed to an IV pole away from the patient and connected to a pressure monitor to display the pressure readings. By locating the pressure transducer to a location relatively close to the connection point of the catheter, more accurate pressure readings can be achieved. Additionally, the weight of the pump mechanism is located on the IV pole, allowing the components near the patient to be relatively lightweight. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects, features and advantages of which embodiments of the invention are capable of will be apparent and elucidated from the following description of embodiments of the present invention, reference being made to the accompanying drawings, in which: 
         FIG. 1  is an overview of an automatic air management system for pressure measurement with an air catheter. 
         FIGS. 2 and 3  illustrate a pump assembly and a pressure transducer assembly of the system of  FIG. 1 . 
         FIG. 4  illustrates a cross section of a pressure transducer assembly cable. 
         FIG. 5  illustrates a cross section of a pressure monitor cable. 
         FIG. 6A-8  illustrate various aspects of an exterior of another embodiment of a pump assembly. 
         FIGS. 9 and 10  illustrate an interior of the pump assembly of  FIG. 6A . 
         FIGS. 11 and 12  illustrate a pump manifold and pumps from  FIG. 9 . 
         FIG. 13  illustrates an air catheter. 
         FIGS. 14 and 15  illustrate an outside view of a pressure transducer assembly. 
         FIGS. 16-19  illustrate various views of an interior of the pressure transducer assembly of  FIG. 14 . 
         FIG. 20  illustrates a pressure transducer assembly and pressure transducer assembly cable. 
         FIG. 21  illustrates a pressure monitor cable. 
         FIG. 22  illustrates a flow chart describing the process of priming the system with a specific amount of air. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Specific embodiments of the invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like numbers refer to like elements. 
     The present invention is generally directed to a powered or automatic air management system  100 , as seen in  FIG. 1 , for measuring pressure from an air pressure catheter  101  located within a patient  10 . While prior art air management systems, such as those in U.S. Pat. No. 8,360,988, require a user to manually charge the pressure system with a known volume of air (i.e., by moving a piston by hand), the present embodiment includes powered pumps to automatically adjust the air volume to a desired level. Additionally, while prior systems include the system&#39;s pressure transducer, manual pumps, and other components in a single enclosure, the present embodiment includes a pressure transducer assembly  102  that is located at the bed of the patient and a separate pump assembly  104  that is fixed to an IV pole  12  that is away from the patient (e.g., 6 feet) and connected to a pressure monitor  106  (e.g., 10 feet maximum from the patient) to display the pressure readings. By locating the pressure transducer to a location relatively close to the connection point of the catheter, more accurate pressure readings can be achieved. 
     It should be noted that the present automatic air management system  100  can be used in connection with measuring pressure at any location within a human body, it is especially useful for measuring intracranial pressure (ICP), which is often measured in connection with treatment of traumatic brain injury. 
     One embodiment of the pump assembly  104  and the pressure transducer assembly  102  are illustrated in  FIG. 2  (general overview) and  FIG. 3  (schematic view of the system&#39;s air passage). The air passage of the system is represented by the connecting lines in  FIG. 3 , of which various components are connected. The pump assembly  104  includes two solenoid pumps  128  and  130  (e.g., 50 μL pumps) connected to the passage, as well as a pump assembly valve  131  and a filter  132 . The valve  131  opens or closes the passage from opening to the atmosphere through the filter  132 , while the pumps  128  and  130  are connected to the air passage on the opposite side of the valve  131 . 
     The air passage further connects to the pump connector socket  126 , which contains pneumatic and electrical connections that connect to the transducer assembly cable  110 . One specific example of the layout of the transducer assembly cable  110  can be seen in  FIG. 4 . Cables  110 A are an electrical conduit that provide power from the pump assembly  104  to the pressure transducer assembly  102 , Cables  1106  transmit the pressure signal from the pressure transducer  136  to the pump assembly  104 , cables  110 C provide power from the pump assembly  104  to the valve  138 , and pneumatic conduit  110 D provides a pneumatic connection from the pump assembly  104  to the pressure transducer assembly  102 . 
     The transducer assembly cable  110  connects to the transducer assembly  102  via connector  134 . As seen in  FIGS. 2 and 3 , the air passage initially splits off to connect to a check valve  140  that vents to atmosphere via filter  142 . The passage also connects to a valve  138  that opens or closes the air passage at that location. On the other side of the valve  138 , the air passage connects to a pressure transducer  136  and to the catheter connector  144 . Finally the air catheter  101  connects to the connector  144 , allowing the air passage to connect to the air passage and air bladder within the catheter  101 . 
     The operation of the components of both the pressure transducer assembly  102  and the pump assembly  104  are preferably controller by a control assembly, which are preferably components on a printed circuit board  112 . For example, the printed circuit board  112  may include a microprocessor that executes firmware and/or software stored in a memory that, when executed, performs the functions described in this specification. The circuit board  112  may also be connected to “zero monitor” button  118  to allow a user to zero out the pressure signal to the monitor  106 , a “prime system” button  120  that allows a user to inject the desired amount of air into the system, and a “stop” button  24  that allows a user to stop the pump assembly  104 . While not shown in  FIGS. 2 and 3 , an alarm LED and an “alarm pause” button can also be included, which indicate a problem with the system and provide a mechanism to stop the alarm, respectively, in such a situation. 
     Further, the circuit board  112  is connected to monitor connector socket  144  that connects with the pressure monitor cord  108  so as to communicate with the monitor  106  (e.g., via one of the electrical conduits  108 A or  1086  in  FIG. 5 ), to a battery  124  via connector  116  to power the system, to the solenoid pumps  128  and  130 , the valves  138 , and to the transducer  136 , to control pressure within the system and provide pressure measurement, respectively. With regard to the electrical conduits  108 A and  1086 , the patient monitor excitation on these conduits wakes up the system  100  for operation and sends voltage to the pressure transducer assembly  102  and receives the pressure signal from the transducer assembly  102 . 
     It should be noted that the automatic air management system  100  and the catheter  101  must have, not only a known amount of air, but an amount that does not over or under inflate the air bladder of the catheter  101 . For example, if the system is over inflated, the resulting pressure readings will be greater than the pressure external to the catheter within the patient&#39;s body (e.g., intracranial pressure). If the system is under inflated, the pressure within the catheter  101  will read less than that within the patient&#39;s body, especially with high pressures in the patient. 
     In the present embodiment, the pressure within the system  100  is maintained via three main pump cycles. The first is the evacuation cycle in which the valve  138  is opened and the solenoid pumps  128  and  130  displace volume within the air passage (e.g., by 100 μL), thereby pulling residual air from the air passage of the catheter  101 . The valve  138  is then closed, sealing off the air passage within the catheter  101 . 
     The second cycle is the injection cycle, in which the valve  138  is again opened and the solenoid pumps  128  and  130  are again actuated to displace volume within the air passage (e.g., by 100 μL), thereby pulling more residual air from the air passage of the catheter  101 . This lowers the pressure within the air passage to a negative pressure equal to the crack pressure of the check valve  140  (e.g., 4 kPa). Next, the solenoid pumps  128  and  130  again displace volume so as to decrease the system volume (e.g., by 100 μL), thereby increasing the amount of air in the catheter  101 . 
     The third cycle is the air optimization cycle, in which a decision point occurs. If the pressure is above a predetermined level (e.g., 40-60 mmHg or greater), the valve  138  closes. If the pressure is less than a predetermined level (e.g., 40-60 mmHg or less), one of the solenoid pumps  128  or  130  displaces volume (e.g., by 50 μL), increasing the system volume, and removing air from the system. The valve  138  then closes and there pressure transducer  136  begins monitoring the pressure. 
     As seen with regard to the air optimization cycle described above, having two solenoid pumps  128  and  130  allows more granularity when inflating and deflating the air bladder of the catheter  101 . This can allows the system to better compensate for dilating in low pressure environments or high pressure environments without adding or extracting excessive volumes of air. Hence, the optimal amount of air can be present within the bladder of the catheter  101  at any pressure. 
     In another aspect of the present invention, the software executed by the microprocessor can detect connection and disconnection of the catheter  101  from the pressure transducer assembly  102 . For example, if the transducer  136  detects a positive pressure spike, the catheter may have been recently connected. If the transducer  136  detects a negative pressure spike, the catheter may have been disconnected. This detection may also result in an indicator on either the pump assembly  104  or the transducer assembly  102  indicating either state to the user (e.g., via a changing color or flashing of an LED). Alternately, the catheter detection can be achieved by an optical sensor, mechanical switch, or an electromechanical sensor (e.g., a Halls-effect sensor). 
       FIGS. 6A-23  illustrate various aspects of another embodiment of an automatic air management system  180  that is generally similar to the previously described embodiment  100 . Turning first to  FIGS. 6A and 6B , the pump assembly  104  includes a user interface  146 , a monitor connector  144 , and a transducer assembly connector  126 . This pump assembly  104  can be fixed to and removed from an I.V. pole  12 . 
       FIG. 6B  illustrates an enlarged view of the user interface  146  that indicates and performs various functions and aspects of the system  180 . Specifically, a “Zero Monitor” LED indicator and button causes the pump to zero out the monitor  106  prior to use, ensuring an accurate pressure will be displayed. Next, a “Connect Catheter” LED indicator indicates whether the catheter  101  is connected to the pressure transducer assembly  102 . This connection status can be sensed via a pressure measurement (e.g., the pressure is equal to the outside atmosphere) or via a mechanical mechanism on the transducer assembly  102  (e.g., a button or switch). A “Prime System” LED indicator and button allows the user to activate the pump assembly  104  to inject the desired amount of air into the air passage and catheter  101 , so that pressure measurement can take place. A battery indicator is also shown, indicating an estimated battery level (e.g., via a plurality of vertical LEDs). Next, an “Alarm” LED indicator and “Alarm Pause” button indicate to the user that problem exists with the system, such as the pressure measurement is out of normal range or that the battery is critically low, and that such an alarm can be temporarily paused. Finally, a “Stop” button stops operation of the pump assembly  104 . 
       FIGS. 7 and 8  illustrate a back and top view of the pump assembly  104 , including two pivoting clamp members  150  that engage the I.V. pole, locking the pump assembly  104  in place. Preferably, the back area of the pump assembly  104  and each of the clamp members  150  are curved so as to accommodate the diameter of the pole  12 . The clamp members  150  can be biased to a closed state (e.g., with springs as seen in  FIG. 10 ) and/or can be lockable in position to prevent the pump assembly  104  from falling off. The clamp members  150  preferably have a relatively soft, elastomer layer that faces the IV pole  12 , thereby increasing the friction with the pole. 
       FIG. 9  illustrates a side view of the interior of the pump assembly  104  and  FIG. 10  illustrates an exploded view of the assembly  104 . The components of the pump assembly  104  are all contained within a front enclosure  104 A and a back enclosure  104 B. The circuit board  112  abuts the front enclosure  104 A and preferably includes the button mechanisms and LEDs that are seen on the front user interface  146 . 
     Beneath the circuit board  112 , at the lower portion of the pump assembly  104  is the battery enclosure  124  that contains one or more batteries to power the pump assembly  104 . Near the lower end of the enclosure  124  is a pair of wires that connect to the circuit board  112 , providing it power. 
     Beneath the circuit board  112 , at the upper portion of the pump assembly  104  are solenoid pumps  128  and  130  (e.g., 50 μL or 65 μL pumps), which are connected to a pump manifold  129 .  FIGS. 11 and 12  illustrate these components in greater detail. The ports of the pumps  128 ,  130  both connect to a first internal manifold passage that connects to both the main air passage of the system (i.e., the passage connecting to the catheter  101 ) and to the output filter  142 . A valve  160  opens or closes this first internal manifold passage to the filter  142  and therefore to the atmosphere within the pump assembly  104 , thereby allowing the pumps to selectively discharge air to the atmosphere. The pump manifold also includes a second internal manifold passage that is connected to an air intake passage to the transducer assembly  102  (described later in this specification) and to the input filter  140 , which allows air to flow from the pump assembly  104  to the transducer assembly  102 . 
     As best seen in  FIG. 10 , the circuit board  112  is connected via wires to the pumps  128 ,  130  to allow for their actuation, to the transducer assembly connector  144  to provide power and receive the transducer data, and to monitor connector  126  to provide pressure data to the monitor. 
       FIG. 13  illustrates an example air pressure catheter  101  having an air bladder  101 A, a catheter tube  101 B with an internal air passage, and a connector assembly  101 C that connects with the connector assembly  152  of the transducer assembly  102 . 
       FIGS. 14-19  illustrates various aspects of the pressure transducer assembly  102 . As seen in  FIG. 15 , the assembly  102  includes an indicator  160  which includes one or more LEDs that indicate if the catheter  101  is properly connected. As seen best in  FIGS. 16 and 17 , the connector assembly  152  includes a biased latching mechanism  152 B that maintains the catheter&#39;s connector assembly  101 C in a locked configuration. A removable protective cover  152 A is located over the latch  152 B, thereby protecting from accidental disconnection of the catheter  101 . Additional details of the connection mechanism can be found in U.S. patent Ser. No. 14/643,997, the contents of which are incorporated herein by reference. 
     As best seen in  FIGS. 16-18 , the air passage of the catheter  101  continues through the passage  154  of the manifold  156 , downwards, then up into a bottom port of the pressure transducer  158 . Preferably, the diameter of the passage  154  is small, such as 0.0020″, to help minimize the amount of the air passage volume and therefore provide optimal air volume within the catheter bladder at different external pressures and thereby offering more accurate pressure readings. 
     The passage within the transducer  158  then further connects with solenoid valve  162 , which either closes off the tranducer&#39;s passage during operation, or opens up the passage during priming. The solenoid valve  162  is then connected to a manifold passage  156 A within the manifold  156 , best seen in  FIG. 19 . The passage  156 A has two ports  1568  and a check valve  166 . One of the ports  156 B is connected to the solenoid valve  162 , while the other is connected to the pneumatic conduit in the cable  110  that leads to the pump assembly  104 . In this respect, the passage  156 A provides communication with the main air passage and the check valve  166 . 
     When the check valve  166  is caused to be opened (e.g., at a predetermined negative pressure), it takes in air from within area  164 . Area  164  is in communication with intake passage  168 , which connects to the second passage in the pump manifold  129 , which ultimately leads to the input filter  140 . Hence, the area  164  is in communication with the atmosphere, allowing the check valve  166  to intake air. 
     As best seen in  FIG. 18 , in addition to the main air passage and the air intake passage, a plurality of electrical wires are also connected within the transducer assembly  102  for powering the valve  162 , powering and communicating with the transducer  158 , and powering the indicator  160 . 
       FIG. 20  illustrates another view of the pressure transducer assembly  102  and cable  110 .  FIG. 21  illustrates another view of the monitor cable  108 . 
       FIG. 22  illustrates a flow chart for priming the previously discussed system  180 . In step  200 , the system vents to atmosphere. Specifically, valve  162  and valve  160  are both opened, allowing the entire main air passage to equalize with the atmospheric pressure. 
     In step  202 , evacuation occurs. First, valve  160  is closed (valve  162  remains open). Next, solenoid pumps  128 ,  130  are activated so as to increase the overall volume in the system (i.e., suck out some of the air from the main air passage). Finally, valve  162  is closed, isolating the passage  154  and the passage within the catheter  101 . 
     In step  204 , recharging occurs. First, valve  160  is opened and the pumps  128 ,  130  are activated so as to decrease the overall volume, pushing air out via fileter  142 . Valve  160  is then closed to seal off the main air passage. 
     In step  206 , evacuation occurs again. First, valve  160  is closed (valve  162  remains open). Next, solenoid pumps  128 ,  130  are activated so as to increase the overall volume in the system (i.e., suck out some of the air from the main air passage). Finally, valve  162  is closed, isolating the passage  154  and the passage within the catheter  101 . If the negative air pressure in the main air pressure passage exceeds the crack pressure of the check valve  166  (such as a pressure between 40-60 mm Hg), the check valve  166  will open, taking in air from area  164 , until the air pressure within the main air passage reaches that crack pressure and the valve  166  closes. At this time, the pump assembly  104  monitors the pressure in the main air passage to determine if it indeed reached the desired level of the crack pressure of the valve. If not, the evacuation step is performed again. 
     Once the desired pressure has been achieved (i.e., the crack pressure of check valve  166 ), a partial system volume to atmosphere step  208  is performed. Valve  160  is opened (valve  162  remains closed) while only solenoid pump  128  is activated so as to increase the overall volume in the main air passage. Next, valve  160  is closed, closing off communication with the input filter  142 . 
     In step  210 , a single pump injection is performed. First, valve  162  is opened, allowing access to passage  154  and to the air passage of the catheter  101 . Next, the pump  128  is activated so as to decrease the volume in the main air passage, thereby injecting additional air into the system. 
     Finally, in the run mode step  212 , the valve  162  is closed, isolating the transducer  158 , the passage  154 , and the passage within the catheter  101 . At this time, the volume of air and pressure in the passage is known. As the pressure within the patient (e.g., within the cranium of the patient) pushes on the flexible bladder  101 A of the catheter  101 , the pressure within the patient can also be calculated according to Boyle&#39;s Law (P 1 V 1 =P 2 V 2 ). 
     Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.