# Patent

## Title
System for detecting and removing a gas bubble from a vascular infusion line

## Abstract

System for detecting and removing gas bubbles from a vascular infusion line, including a cassette adapted for disposition intermediate the fluid line, the cassette including a flexible tube having an inlet port for connection to a supply side of the fluid line, an outlet port configured for connection to a patient side of the fluid line, and a purge port intermediate the inlet and outlet ports, and a base unit adapted to receive the cassette and monitor fluid flow through the tube, the base unit including a sensor to detect the presence of a gas bubble in the fluid flow, a pinch valve adapted to stop the flow of fluid, and a control unit adapted to operate the base unit so that (i) fluid is permitted to flow past the pinch valve when no gas bubble is detected; and (ii) fluid flow is arrested when a gas bubble is detected.

## Background
REFERENCE TO PENDING PRIOR PATENT APPLICATIONS
This patent application is a division of pending prior U.S. patent application Ser. No. 11/134,894, filed May 23, 2005 by Ihsan A. Haddad et al. for SYSTEM FOR DETECTING AND REMOVING A GAS BUBBLE FROM A VASCULAR INFUSION LINE, which in turn claims benefit of:
(i) prior U.S. Provisional Patent Application Serial No. 60/573,311, filed May 21, 2004 by Ihsan A. Haddad et al. for AIRTRAP ONE; and
(ii) prior U.S. Provisional Patent Application Serial No. 60/630,471, filed Nov. 23, 2004 by Ihsan A. Haddad et al. for ANESTHESIA SAFETY PRODUCTS.
The above-identified patent applications are hereby incorporated herein by reference.


FIELD OF THE INVENTION
This invention relates to medical apparatus and procedures in general, and more particularly to medical apparatus and procedures for introducing a liquid into the vascular system of a patient.
BACKGROUND OF THE INVENTION
When a patient is undergoing a medical procedure that requires the infusion of a liquid into their circulatory system, be it venous or arterial, the introduction of a significantly-sized gas bubble (also known as a “gas volume”, or a “gas bolus”, etc.) into the patient's vascular system must be avoided, since the creation of a gas embolism can result in serious morbidity and even death.
There are two general categories of gas embolisms: venous and arterial. The primary difference between the two depends on the path by which the gas enters the vascular structure.
There are two general causes for the introduction of gas into either the arterial or venous systems:
(i) from instrumentation, such as accidental air injection through tubing, catheters, injectors, fluid warmers, etc.; and
(ii) from physical conditions relating to the patient, such as sub-atmospheric pressure in incised non-collapsed veins or veins in a coagulated operative field, etc.
Available data indicates that 2 cc's of air per kilogram of body weight, if injected into the venous system, is lethal. Smaller amounts can cause various degrees of morbidity. To put this in perspective, the air in an empty 4 ounce cup, if injected into the veins of a 170 pound person, would typically prove lethal.
Thus, there is a need for a system for detecting and removing a gas bubble from a liquid infusion line prior to the gas bubble entering the vascular system of the patient.
SUMMARY OF THE INVENTION
The present invention provides a novel system for detecting and removing a gas bubble from a liquid infusion line before the gas bubble can enter the vascular system of the patient. Among other things, the system is adapted to stop the flow of fluid carrying the entrapped gas bubble, and to allow for the extraction of the gas bubble prior to permitting the fluid to enter the patient's circulatory system.
In another aspect of the present invention, there is provided a novel method and apparatus for detecting a gas bubble in a fluid line, entrapping the gas bubble, and purging the gas bubble from the fluid line before the gas bubble can enter the patient's vascular system.
In another aspect of the present invention, there is provided a system for detecting and removing a gas bubble from a vascular infusion line, the system comprising:
a disposable cassette adapted for disposition intermediate the fluid line, the disposable cassette comprising:

    
    
        a body; and
        a flexible hollow tube having an inlet port being configured for connection to the supply side of the fluid line, an outlet port being configured for connection to the patient side of the fluid line and a purge port located intermediate the inlet port and the outlet port;
    
    


a base unit adapted to receive the disposable cassette and monitor fluid flow through the flexible hollow tube, wherein the base unit comprises:

    
    
        a sensor adapted to detect the presence of a gas bubble in the fluid flowing through the flexible hollow tube; and
        a pinch valve adapted to stop the flow of fluid through the flexible hollow tube; and
    
    


an electronic control unit adapted to operate the base unit so that (i) fluid is permitted to flow past the pinch valve when no gas bubble is detected by the sensor; and (ii) fluid flow is arrested when a gas bubble is detected by the sensor.
In another aspect of the present invention, there is provided a system for detecting a gas bubble from a vascular infusion line, the system comprising:
a cassette adapted for disposition intermediate the fluid line, the cassette comprising:

    
    
        a body; and
        a passageway having an inlet port being configured for connection to the supply side of the fluid line, and an outlet port being configured for connection to the patient side of the fluid line; and
        a first portion of a valve for selectively arresting fluid flow through the passageway;
    
    


a base unit adapted to receive the cassette and monitor fluid flow through the passageway, wherein the base unit comprises:

    
    
        a sensor adapted to detect the presence of a gas bubble in the fluid flowing through the passageway; and
        a second portion of a valve for selectively arresting fluid flow through the passageway; and
    
    


an electronic control unit adapted to operate the second portion of the valve so that (i) fluid is permitted to flow past the first portion of the valve when no gas bubble is detected by the sensor; and (ii) fluid flow is arrested when a gas bubble is detected by the sensor.
In another aspect of the present invention, there is provided a method for detecting and removing a gas bubble from a vascular infusion line, the method comprising:
providing a system comprising:
a disposable cassette adapted for disposition intermediate the fluid line, the disposable cassette comprising:

    
    
        a body; and
        a flexible hollow tube having an inlet port being configured for connection to the supply side of the fluid line, an outlet port being configured for connection to the patient side of the fluid line and a purge port located intermediate the inlet port and the outlet port;
    
    


a base unit adapted to receive the disposable cassette and monitor fluid flow through the flexible hollow tube, wherein the base unit comprises:

    
    
        a sensor adapted to detect the presence of a gas bubble in the fluid flowing through the flexible hollow tube; and
        a pinch valve adapted to stop the flow of fluid through the flexible hollow tube; and
    
    


an electronic control unit adapted to operate the base unit so that (i) fluid is permitted to flow past the pinch valve when no gas bubble is detected by the sensor; and (ii) fluid flow is arrested when a gas bubble is detected by the sensor;
initiating fluid flow through the disposable cassette; and
monitoring the fluid flowing through the disposable cassette for the occurrence of a gas bubble and, if a gas bubble is detected, arresting the flow of fluid through the fluid line.
In another aspect of the present invention, there is provided a method for detecting a gas bubble from a vascular infusion line, the method comprising:
providing a system comprising:
a cassette adapted for disposition intermediate the fluid line, the cassette comprising:

    
    
        a body; and
        a passageway having an inlet port being configured for connection to the supply side of the fluid line, and an outlet port being configured for connection to the patient side of the fluid line; and
        a first portion of a valve for selectively arresting fluid flow through the passageway;
    
    


a base unit adapted to receive the cassette and monitor fluid flow through the passageway, wherein the base unit comprises:

    
    
        a sensor adapted to detect the presence of a gas bubble in the fluid flowing through the passageway; and
        a second portion of a valve for selectively arresting fluid flow through the passageway;
    
    


an electronic control unit adapted to operate the second portion of the valve so that (i) fluid is permitted to flow past the first portion of the valve when no gas bubble is detected by the sensor; and (ii) fluid flow is arrested when a gas bubble is detected by the sensor;
initiating fluid flow through the cassette; and
monitoring the fluid flowing through the cassette for the occurrence of a gas bubble and, if a gas bubble is detected, arresting the flow of fluid through the fluid line.
In another aspect of the present invention, there is provided a system for detecting and removing a gas bubble from a flexible vascular infusion line, the system comprising:
a cassette adapted for disposition intermediate the fluid line, the cassette comprising:

    
    
        a body; and
        a passageway having an inlet port being configured for connection to the supply side of the fluid line and an outlet port configured for connection to the patient side of the fluid line;
    
    


a base unit adapted to receive the cassette and monitor fluid flow through the passageway, wherein the base unit comprises:

    
    
        a sensor adapted to detect the presence of a gas bubble in the fluid flowing through the passageway;
    
    


an electronic control unit disposed adjacent to the flexible fluid line, upstream of the cassette, wherein the electronic control unit comprises a valve for selectively arresting fluid flow through the flexible fluid line and circuitry for communicating with the sensor and operating the valve so that (i) fluid is permitted to flow through the flexible fluid line when no gas bubble is detected by the sensor; and (ii) fluid flow through the flexible fluid line is arrested when a gas bubble is detected by the sensor; and
a purge port located upstream of the patient and downstream of the electronic control unit.
In another aspect of the present invention, there is provided a method for detecting and removing a gas bubble from a flexible vascular infusion line, the method comprising:
providing a system comprising:
a cassette adapted for disposition intermediate the fluid line, the cassette comprising:

    
    
        a body; and
        a passageway having an inlet port being configured for connection to the supply side of the fluid line and an outlet port configured for connection to the patient side of the fluid line;
    
    


a base unit adapted to receive the cassette and monitor fluid flow through the passageway, wherein the base unit comprises:

    
    
        a sensor adapted to detect the presence of a gas bubble in the fluid flowing through the passageway;
    
    


an electronic control unit disposed adjacent to the flexible fluid line, upstream of the cassette, wherein the electronic control unit comprises a valve for selectively arresting fluid flow through the flexible fluid line and circuitry for communicating with the sensor and operating the valve so that (i) fluid is permitted to flow through the flexible fluid line when no gas bubble is detected by the sensor; and (ii) fluid flow through the flexible fluid line is arrested when a gas bubble is detected by the sensor; and
a purge port located upstream of the patient and downstream of the electronic control unit;
initiating fluid flow through the flexible fluid line and through the cassette; and
monitoring the fluid flowing through the cassette for the occurrence of a gas bubble and, if a gas bubble is detected, arresting the flow of fluid through the flexible fluid line.



BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which are to be considered together with the accompanying drawings wherein like numbers refer to like parts, and further wherein:
FIG. 1 is a schematic view showing a disposable cassette formed in accordance with the present invention;
FIGS. 2-4 are schematic views showing components of the disposable cassette shown in FIG. 1;
FIG. 5 is a schematic view showing a base unit formed in accordance with the present invention;
FIG. 6 is a schematic view showing a component of the base unit shown in FIG. 5;
FIGS. 7 and 8 are schematic views showing the disposable cassette of FIG. 1 mounted on the base unit of FIG. 5;
FIG. 9 is a schematic view showing the disposable cassette's sensor loop and delay loop;
FIG. 10 is a schematic view showing an electronic control unit formed in accordance with the present invention;
FIG. 11 is a schematic view showing an alternative form of the disposable cassette;
FIG. 12 is a schematic view showing the tubing component of the disposable cassette shown in FIG. 11;
FIG. 13 is another schematic view of the disposable cassette shown in FIG. 11;
FIG. 14 is a schematic view showing an alternative form of base unit;
FIGS. 15 and 16 are schematic views showing the disposable cassette of FIGS. 11 and 13 in conjunction with the base unit of FIG. 14;
FIGS. 17 and 18 are schematic views showing an alternative form of the disposable cassette;
FIGS. 19 and 20 are schematic views showing an alternative form of the base unit;
FIG. 21 is a schematic view showing the disposable cassette of FIGS. 17 and 18 in conjunction with the base unit of FIGS. 19 and 20;
FIG. 22 is a schematic view showing an alternative form of the disposable cassette;
FIGS. 23 and 24 are schematic views showing the disposable cassette of FIG. 22 in conjunction with an alternative base unit;
FIG. 25 is a schematic view showing another alternative form of the disposable cassette;
FIGS. 26-34 are various schematic views showing another preferred embodiment of the new system for detecting a gas bubble in a fluid line, entrapping the gas bubble, and purging the gas bubble before the gas bubble can enter the patient's vascular system;
FIG. 35 is a schematic view showing an alternative disposable cassette in conjunction with an alternative base incorporating the sensing unit for remote mounting;
FIG. 36 is a schematic view of an alternative electrical control unit incorporating a pinch valve; and
FIG. 37 is a schematic view showing a system configuration where the alternative disposable cassette of FIG. 35, the alternative base unit of FIG. 35, and the alternative electrical control unit of FIG. 36 are all mounted on an IV pole.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention provides a novel system for detecting a gas bubble in a fluid line, entrapping the gas bubble, and purging the gas bubble before the gas bubble can enter the patient's vascular system.
In one preferred form of the invention, the novel system comprises three components: (i) a disposable cassette for disposition intermediate the fluid line, wherein fluid flowing through the disposable cassette may be monitored and, if a gas bubble is detected within the fluid flow, the fluid flow may be stopped and the gas bubble removed before continuing the fluid flow; (ii) a base unit providing apparatus for monitoring the fluid flow through the disposable cassette and, if a gas bubble is detected, selectively stopping the fluid flow through the disposable cassette while the gas bubble is removed; and (iii) an electronic control unit for operating the base unit.
More particularly, and looking now at FIGS. 1-4, there is shown a disposable cassette 5 which comprises one preferred form of the invention. Disposable cassette 5 is adapted for disposition intermediate the fluid line (e.g., an IV line), wherein fluid flowing through the disposable cassette may be monitored and, if a gas bubble (e.g., an air bubble) is detected within the fluid flow, the fluid flow may be stopped and the gas bubble removed before continuing the fluid flow. Disposable cassette 5 comprises a body 10 including tubing 15 (FIG. 1). Tubing 15 has an inlet port 20, and outlet port 25, and a purge port 30. Body 10 and tubing 15 are arranged so that tubing 15 is exposed at a sensor station 35 and at a pinch location 40 (e.g., with openings). Inlet port 20 and outlet port 25 are configured with an appropriate fitting (i.e., Luer, male, female, locking “T”, stopcock, etc.) so that the tubing 15 of the disposable cassette 5 can be connected intermediate a fluid line entering the patient. Purge port 30 provides selective access (e.g., via a removable cap) to the interior of tubing 15, whereby to permit removal of a gas bubble in the fluid line, as will hereinafter be discussed. In one preferred form of the invention, disposable cassette 5 can be formed by providing a groove 45 in body 10 (FIG. 2), wherein groove 45 is configured to receive tubing 15 (FIG. 3), with a cover 50 (FIG. 4) securing the tubing 15 within groove 45.
Body 10 and cover 50 are preferably formed out of medical grade, soft or semi-soft, sterilizable, clear or transparent or semi-transparent, plastic such as PVC, a urethane, etc.
Tubing 15 is preferably a clear plastic FDA Class 6 tubing with a durometer consistent with the “pinch” requirements of the base unit's pinch valve, as will hereinafter be discussed. Tubing 15 is sized so as to be consistent with the flow requirements of the IV fluid line. By way of example but not limitation, for adults and high flow IV requirements, a tube 15 having a 1⁄8 inch inside diameter, and a 3/16 inch outside diameter, may be used.
Preferably the disposable cassette 5 is provided to the user in a pre-assembled form (i.e., with tubing 15 loaded into groove 45 and sealed in place with cover 50), with the disposable cassette being sealed in a sterilized package which is opened at the time of use.
Looking next at FIGS. 5-9, there is shown a base unit 100 which comprises one preferred form of the invention. Base unit 100 is adapted to receive disposable cassette 5 and monitor the fluid flow through the disposable cassette and, if a gas bubble is detected, selectively stop the fluid flow through the disposable cassette while the gas bubble is removed. Base unit 100 generally comprises a seat 105 (FIG. 5) for seating the disposable cassette 5. Base unit 100 also comprises a sensor 110 for detecting the presence of a gas bubble in the fluid flowing through tubing 15 of the disposable cassette. In one form of the invention, sensor 110 comprises an ultrasound sensor (FIG. 6) and, in one particularly preferred form of the invention, sensor 110 comprises an ultrasound sensor having two halves 110A, 110B hinged together at 110C. Each half 110A, 110B comprises an appropriate rectangular ultrasound crystal C running the length of the face. Base unit 100 also comprises a pinch valve 115 (FIG. 5) for selectively pinching off the tubing 15 of disposable cassette 5, whereby to selectively stop fluid flow through the tubing. By way of example but not limitation, pinch valve 115 may comprise a solenoid having a movable member for (i) engaging the tubing 15 when the movable member is placed into its extended position, whereby to pinch the tubing 15 closed, and (ii) disengaging the tubing 15 when the movable member is placed into its retracted position, whereby to allow the tubing to expand to its full diameter. As seen in FIGS. 7 and 8, disposable cassette 5 and base unit 100 are constructed so that when disposable cassette 5 is received on seat 105, sensor station 35 of disposable cassette 5 is positioned adjacent to sensor 110 of base unit 100, and pinch location 40 of disposable cassette 5 is disposed adjacent to pinch valve 115 of base unit 100.
Significantly, and as will hereinafter be discussed in further detail, due to the switchback configuration of the tubing 15 of disposable cassette 5, two legs of tubing 15 will pass by sensor 110 at sensor station 35 (FIGS. 7 and 9). Thus, tubing 15 will be monitored by sensor 110 at two locations, L1 and L2. The length of tubing 15 extending between the two locations L1 and L2 may be referred to as the “sensor loop” SL.
Furthermore, it will be appreciated that a length of tubing extends between sensor location L2 and purge port 30. This length of tubing provides a “delay loop” DL which will hereinafter be discussed.
Looking next at FIG. 10, there is shown an electronic control unit 200 which comprises one preferred form of the invention. Electronic control unit 200 is adapted to operate base unit 100 as will hereinafter be discussed. Electronic control unit 200 generally comprises a housing 203, an on/off switch 205, a sound off switch 210, a system reset switch 215, a green light 220, a system red light 225, a sound red light 230, an umbilical cord 235 for connecting electronic control unit 200 to base unit 100, and various conventional electronic components (not shown) housed by housing 203 and adapted to operate as will hereinafter be discussed.
Among other things, umbilical cord 235 connects electronic control unit 200 to the base unit's sensor 110 whereby to operate (i.e., power and read) the same, and umbilical cord 235 connects electronic control unit 200 to the base unit's pinch valve 115, whereby to operate (i.e., power and control) the same.
Electronic control unit 200 is preferably internally powered by a 12 volt rechargeable battery pack, although it may also be powered by an external power source, e.g., by connection to a wall plug.
In operation, a disposable cassette 5 is withdrawn from its sterilized package and loaded into base unit 100. This is done by opening sensor 110, seating disposable cassette 5 on the base unit's seat 105 so that the cassette's sensor station 35 is located adjacent to the base unit's sensor 110 and so that the disposable cassette's pinch location 40 is located adjacent to the base unit's pinch valve 115, and then closing sensor 110.
Next, the “source side” of a fluid line (e.g., an IV line) is connected to the cassette's inlet port 20, and the cassette's output port 25 is connected to the “patient side” of the IV line.
The IV line is then primed, air removed, etc. so that the fluid line is ready to infuse the patient.
Then the system is turned on by pushing on/off switch 205.
Next, fluid is allowed to flow from the fluid source into tubing 15 of disposable cassette 5. As the fluid flows through the tubing, sensor 110 monitors the fluid flow, sensing for the presence of a gas bubble. So long as no gas bubble is detected, the fluid is allowed to flow uninterrupted, thereby infusing the patient with the desired fluid. Green light 220 is lit when the system is on and no gas bubble is detected by sensor 110.
In the event that sensor 110 detects the presence of a gas bubble (e.g., an air bubble) in the fluid, electronic control unit 200 turns on red light 225, sounds an audible alarm in electronic control unit 200, and activates pinch valve 115, thereby arresting the fluid flow.
The operator can now activate the sound off switch 210, temporarily turning the alarm sound off, and then use purge port 30 to bleed the gas bubble from the system. As soon as the sensor no longer detects a gas bubble at sensor station 35, indicating that the gas bubble has been purged from the line, green light 220 comes back on, signifying that the system may now be reset. The operator then actuates system reset switch 215, thereby resetting the system. Upon system reset, pinch valve 115 is re-opened, thereby permitting the fluid flow to resume.
In the event that the sound off switch 210 is pushed, but the system fault is not corrected within some specified time period (e.g., one minute), the electronic control unit 200 then turns the sound alarm back on.
In the event that the reset switch 215 is activated, but the fault condition is not corrected, the system will not reset.
It should be appreciated that, as noted above, the disposable cassette's tubing 15 passes by sensor 110 at two locations, i.e., L1 and L2.
If desired, the system can be configured such that sensor 110 and electronic control unit 200 trigger a fault condition when a gas bubble is detected at either location L1 or L2.
More preferably, however, the system is configured such that sensor 110 and electronic control unit 200 trigger a fault condition only when a gas volume is simultaneously detected at both locations L1 and L2. This configuration can be advantageous, inasmuch as simultaneously detecting a gas bubble at both locations L1 and L2 can be indicative of the presence of a large gas bubble in the fluid line, i.e., one completely filling the sensor loop SL. As a result, by configuring the disposable cassette 5 so that its sensor loop SL is of a pre-determined size, the system can discriminate between gas bubbles of different sizes, activating the fault condition only when the gas bubble exceeds a certain size. In other words, in this form of the invention, the length of the sensor loop SL, and its internal volume, determines the amount of gas that can be present in the circuit before the fault condition is triggered. This feature can be advantageous, inasmuch as adults may be capable of safely tolerating a larger gas bubble than an infant, etc. Furthermore, gas bubbles commonly exist in most IV circuits; tiny gas bubbles are generally deemed harmless, and it is only the larger gas bubbles which are considered to pose a threat to the patient. By making the system capable of discriminating between different bubble sizes when determining a fault condition, false positives can be minimized without sacrificing system usefulness.
In one preferred form of the invention, sensor loop SL is configured to have a volume of 1 cc.
It should also be appreciated that various system components typically have response time delays associated with them. Thus, for example, there is typically a delay between when a fault condition occurs at locations L1 and/or L2, and when the fault condition is detected by sensor 110, and when the pinch valve 115 can be closed. To this end, it is advantageous to provide a delay loop DL between sensor station 35 and purge port 30. By properly setting the length of delay loop DL relative to the aggregated response delay times of the system components, the system can be provided with the capacity to timely stop the fluid flow and reliably trap the undesirable gas volume in the delay loop for safe removal of the same.
In one preferred form of the invention, delay loop DL is configured to have a length of 10 cm.
Disposable cassette 5 is preferably discarded after use.
Looking next at FIGS. 11-16, there are shown alternative constructions for disposable cassette 5 and base unit 100. Among other things, this form of the invention utilizes (i) a different and more compact geometry than that shown in FIGS. 1-10; (ii) a one-piece sensor 110; and (iii) a vacuum-formed cassette body 10 which encompasses portions of tubing 15, whereby to eliminate the use of body grooves 45 and cover 50.
Looking next at FIGS. 17-21, there are shown other alternative constructions for disposable cassette 5 and base unit 100. Among other things, this form of the invention utilizes (i) a different and more compact geometry than that shown in FIGS. 1-16; (ii) a disposable cassette 5 omitting the large planar body 10 and cover 50, with tubing 15 in the form of an inline stacked configuration and secured together (e.g., with glue, molding techniques, etc.) so as to form the structure of disposable cassette 5 (here, the securing structure can be thought of as constituting the body 10); and (iii) a base unit 100 modified to receive the modified disposable cassette 5.
Looking next at FIGS. 22-24, there are shown further alternative constructions for disposable cassette 5 and base unit 100. Among other things, this form of the invention utilizes (i) a different and more compact geometry than that shown in FIGS. 1-21; (ii) a disposable cassette 5 having an L-shaped body 10, with tubing 15 in the form of an inline stacked coil configuration and secured together (e.g., with glue, molding techniques, etc.); and (iii) a base unit 100 utilizing a manually cocked pinch valve 115. This manual pinch valve construction can be advantageous in further reducing the size of the pinch valve and hence reducing the size of the base unit 100. In this embodiment of the invention, after fault detection and correction, the system has to be reset manually by compressing the valve's spring-loaded pinch bar until it is cocked in place. Upon the detection of a gas bubble in the sensor loop, the locking mechanism is electronically released.
Looking next at FIG. 25, it will be seen that the geometry of the disposable cassette's tubing 15 can be arranged as desired so as to provide the desired sensor loop SL and delay loop DL.
Looking next at FIGS. 26-34, there is shown still another novel system for detecting and removing a gas bubble from a liquid infusion line. In this form of the invention, the base unit 100 and the electronic control unit 200 are contained in the same housing. Also shown is a detachable battery pack 300 for powering the system.
System with Automatic Fluid Diversion
The system described above is adapted to stop fluid flow to the patient upon the detection of a gas bubble, and then requires the operator to intervene by manually bleeding the gas bubble out of the line and then resetting the system.
In an alternative construction, this intervention is automated in the sense that, upon detection of a gas bubble, the flow of liquid (e.g. IV liquid) is diverted to a collection bag until the sensor 110 once again detects liquid in the IV line. When sensor 110 again detects liquid in the IV line, the gas bubble between sensor 110 and the flow diverting mechanism is flushed out of the system before flow is diverted back to the patient. This can be accomplished in various ways. By way of example but not limitation:
(i) at the onset of a procedure, the operator can set a control on the electronic control unit 200 to reflect the estimated IV flow rate—this flow rate sets a time delay for the diverting mechanism, whereby to delay the diversion of the flow back to the patient after sensor 110 once again detects liquid; or
(ii) a second gas bubble sensor (not shown) can be positioned in the system, at the diverting mechanism, to control switching the fluid flow back to the patient after sensor 110 and the second gas bubble sensor both detect liquid in the line.
The diverting mechanism can take many different forms. For example, the diverting mechanism can be a disposable Y connector molded into the disposable cartridge 5 and an integral part of the disposable cartridge, with the bottom part of the Y connected to sensor 110, downstream from the liquid delay loop DL of the disposable cartridge 5. The second gas bubble sensor is positioned to detect a gas bubble in the central part of the Y. A two-sided pinch valve 115 is attached to the two top parts of the Y; this pinch valve has two pinching stations, and is arranged so that when one station is open, the other station is closed. A normally open side of pinch valve 115 is positioned at one of the top forks of the Y and the normally closed part of the pinch valve 115 is positioned on the other side of the fork in the top part of the Y. Simple activation of the pinch valve 115 now will allow the flow to be diverted from one side of the disposable cartridge Y to the other. The appropriate side will be connected to the patient; the other side is connected to the collection bag.
A further device configuration would allow for yet a third gas bubble sensor (not shown) to be incorporated in the device. The third gas bubble sensor can be a clamp-on sensor to be positioned on the tubing slightly downstream from the IV bag or other fluid source, to detect when the IV bag is empty, to halt the flow or divert it from the patient and then sound an alarm, signaling an empty IV bag.
In the preceding disclosure, means were disclosed for selectively diverting the flow of fluid away from the patient (when the fluid flow contains a gas bubble) and then an automatic resumption of fluid flow to the patient (when the gas bubble has been purged from the line).
In another form of the invention, the fluid flow, upon detection of a gas bubble, is automatically diverted away from the patient using any of several methods disclosed above or any other suitable means for diverting the gas embolus and maintaining the safety of the patient; but then the fluid flow is not automatically diverted back to the patient but, rather, continues to be directed away from the patient until the attendant resets the device. This will allow the attendant to assess the situation and reset the system when appropriate.
The above embodiments can be incorporated singly or in combination with any of the other system iterations.
An alternate electronic method to trigger the pinch valve 115, or to reroute the fluid flow to a collection bag or back to the patient, entails the electronic calculation of the time the sensor 110 senses a gas bubble in the tubing. By way of example, if a quantity of gas is passing through the sensor 110, an electronic signal signifying “gas” is triggered at the onset of the gas bolus, and the electronic control unit 200 senses the time that the “gas signal” came on. The internal cross-sectional area of the tubing 15 is known. An automatic calculation is performed as to the gas volume passing through the line. If one sensor is used, the gas volume passing through is calculated using an assumed flow rate. This also allows for the calculation of the velocity of the fluid. In turn, this allows for the calculation of the pressure drop in the tubing, allowing for a volume adjustment of the gas flowing through. This calculation is done in real-time and continuously updates its information and, when a predetermined gas volume is sensed, the system triggers its mode of action (e.g., shuts off, alarms, diverts the flow, etc.).
For more precise performance, the use of two sensors in series, positioned a known distance apart, may be utilized. The sensor configuration and positioning should follow the basic parameters of the system, allowing sufficient time for action before releasing the fluid to the patient.
Modifications
Various modifications can be made to the embodiments disclosed above. By way of example but not limitation:
(1) the sensor 110 can use IR (infra red) to detect the presence of a gas bubble;
(2) the sensor 110 can use electrical resistance to detect the presence of a gas bubble;
(3) the sensor 110 can use sound-based technologies (e.g., Doppler technology) to detect the presence of a gas bubble;
(4) the sensor 110 can comprise a float in the liquid circuit to gate fluid flow: with this arrangement, the float rises in the presence of liquid, opening an outlet port, but the float sinks in the presence of a gas bubble, closing an outlet port—a resistance or a magnetic detector then senses the float position and signals a system fault;
(5) safety devices can be incorporated to automatically indicate correct (or incorrect) engagement of the disposable cassette 5 on base unit 100;
(6) an indicator may be provided to show delivery of an adequate tube-pinching force;
(7) a wireless connection may be provided between base unit 100 and electronic control unit 200—thus, for example, and looking now at FIG. 35, a disposable cassette 5 and base unit 100 may be separated from electronic control unit 200, with the units communicating through a wireless connection; or, if desired, the pinch valve 115 may be located with the electronic control unit 200 (FIG. 36) and/or, if desired, disposable cassette 5, base unit 100 and electronic control unit 200 may all be mounted from an IV pole (FIG. 37);
(8) the sensor station 35 of the disposable cassette 5 (which is positioned adjacent to sensor 110) may be treated with an ultrasound coupling medium such as Vaseline, or a water jell, or whatever is appropriate, so as to ensure a satisfactory coupling to the ultrasound sensor 110—the coating may also contain a solvent and/or an abrasive to clean the sensor 110 and sensor station 35;
(9) as an alternative or in combination with the foregoing, means could be provided to clean the sensor 110 as the disposable cassette 5 is mounted adjacent to the sensor 110—by way of example, this could be accomplished by a mechanical shield covering the disposable tubing 15 which, when removed, will clean the sensor cavity;
(10) cassette 5 need not be disposable—it could be reusable if desired;
(11) cassette 5 could be formed with a passageway, wherein only portions of the passageway comprise flexible tubing—the remainder of the passageway could be formed as a flow path through body 10, or as rigid tubing, etc.;
(12) the construction can be something other than flexible tubing and a pinch valve to selectively close off fluid flow—by way of example but not limitation, cassette 5 could include a traditional flow valve, and base unit 100 could include a mechanism (e.g., a solenoid) for opening that flow control valve; and
(13) if desired, the purge port can be omitted.
Further Modifications
It will be appreciated that still further embodiments of the present invention will be apparent to those skilled in the art in view of the present disclosure. It is to be understood that the present invention is by no means limited to the particular constructions herein disclosed and/or shown in the drawings, but also comprises any modifications or equivalents within the scope of the invention.

## Claims

1. A system for detecting, entrapping, and purging a gas bubble from a vascular liquid infusion line, the system comprising:
a cassette adapted for disposition intermediate the infusion line, the cassette comprising:
a body;
a passageway having an inlet port for connection to a supply side of the infusion line, and an outlet port for connection to a patient side of the infusion line and a purge port for removal of the gas bubble;
a valve having a first portion adapted for selectively permitting and arresting fluid flow through said passageway;

a base unit adapted to receive said cassette and to monitor liquid flow through said passageway, wherein said base unit comprises:
an ultrasound sensor comprising first and second halves hinged together, each of said halves comprising an ultrasound crystal, said sensor being adapted to detect the presence of a gas bubble in the liquid flowing through said passageway; and
a second portion of said valve adapted for selectively permitting and arresting fluid flow through said passageway; and
an electronic control unit adapted to operate said second portion of said valve so that (i) liquid is permitted to flow past said first portion of said valve when no gas bubble is detected by said sensor; (ii) liquid flow is arrested by said second portion of said valve when a gas bubble is detected by said sensor; and (iii) the detected gas bubble is removed through said purge port;

wherein two legs of said infusion line are proximate said sensor, such that said sensor is adapted to monitor the infusion line at two locations; and
a length of said infusion line extends between said sensor and said purge port.

2. A system according to claim 1 wherein said valve first portion is formed by providing said passageway with a flexible wall capable of being deformed so as to close off said passageway to liquid flow.

3. A system according to claim 2 wherein said second portion of said valve comprises an actuator for deforming the flexible wall of said passageway.

4. A system according to claim 1 wherein said valve first portion comprises a valve housing, a valve seat and a valve member for selective engagement with said seat, and wherein said second portion of the valve comprises an actuator for moving said valve member.

5. A method for detecting and removing a gas bubble from a vascular infusion line, the method comprising:
providing a system comprising:
a cassette adapted for disposition intermediate the infusion line, the cassette comprising:
a body;
a passageway having an inlet port for connection to a supply side of the infusion line, and an outlet port for connection to a patient side of the infusion line; and
a valve having a first portion adapted for selectively permitting and arresting fluid flow through the passageway; and

a base unit adapted to receive the cassette and to monitor liquid flow through the passageway, wherein the base unit comprises:
an ultrasound sensor comprising first and second halves hinged together, each of said halves comprising an ultrasound crystal, said sensor being adapted to detect the presence of a gas bubble in the liquid flowing through the passageway; and

a second portion of the valve adapted for selectively arresting liquid flow through the passageway; and
an electronic control unit adapted to operate the second portion of the valve so that (i) liquid is permitted to flow past the first portion of the valve when no gas bubble is detected by the sensor, (ii) liquid flow is arrested when a gas bubble is detected by the sensor; and (iii) the gas bubble is purged from the liquid line;
wherein two legs of the infusion line are proximate the sensor, such that the sensor is adapted to monitor the infusion line at two locations; and
a length of the infusion line extends between the sensor and the purge port;
initiating liquid flow through the cassette; and
monitoring the liquid flowing through the cassette for the occurrence of a gas bubble and, if a gas bubble is detected, arresting the flow of liquid through the passageway, and purging the gas bubble from the passageway through a purge port.