Abstract: A soft shell reservoir bag is provided as a storage reservoir for blood in a bypass extracorporeal circuit during open heart surgery. The reservoir bag is constructed to allow for the easy venting of air and to prevent the accidental delivery of air to patient. Blood enters the reservoir through the inlet port, passes through the microscreen and exits through the outlet port to a pump which feeds an oxygenator. The shape of the bag and component disposition give the bag its main advantages. The inlet port is positioned above the outlet port which puts a larger volume above the outlet port which promotes mixing and no vortex. Also the shape above the outlet port gives the bag a low hold-up volume and lower resistance to keep the bag open. The shape also promotes low venous resistance.

Abstract: A system and method is provided which substantially eliminates the effect of air entrapped in tubing for delivering a liquid from a container. The inner diameter of the tubing is selected such that the gravitational force of the liquid from the container is greater than the surface tension of the liquid. A release agent may be used as a coating layer on the interior wall in addition to or alternatively from an expanded diameter.

Abstract: Disclosed is an apparatus for providing liquid to a patient, preventing reflux and permitting venting. Tubes or other suitable apparatus are provided for connecting to the liquid source and the patient. An anti-reflux valve is provided in the hydraulic channel between the source and the patient. A vent is provided in the channel between the anti-reflux valve and the patient. Thus, gas urged from the patient under pressure is urged out of the vent. However, liquid similarly urged from the patient is prevented from overflowing by the anti-reflux valve. In a preferred embodiment, the anti-reflux valve is a flapper valve or a ball valve. In another preferred embodiment, the vent is a gas permeable, liquid impervious fabric. Alternatively, the vent may be a float valve. The invention is useful for gastroenterological feeding, nasogastric feeding and the like.

Abstract: A system and method for connecting a first fluid carrying tube and a second fluid carrying tube or tube fitting includes a first tube having a lumen therethrough and an open end, and a second tube or tube fitting having a lumen therethrough and an open end. The first tube and second tube (or tube fitting) are connected by connecting means, including a bubble elimination chamber, in a first position, wherein the lumen of the tube, the lumen of the connecting means and the lumen of the tube fitting form a fluid-tight circuit and the bubble elimination chamber is open to the circuit, to permit elimination of any bubbles in the fluid circuit to the bubble elimination chamber. The first tube, connecting means and second tube (or tube fitting) then are connected in a second position, wherein a continuous, fluid-tight, bubble-free fluid circuit is formed, and the bubble elimination chamber is closed to the fluid circuit. The connecting means may include a soft connector alone or in combination with a connector tube.

Abstract: This invention provides a method and a noninvasive device for preventing pressure build-up in pleural space and reducing possibility of development of tension pneumothorax from open pneumothorax by providing a rigid, tubular base firmly attached to an annular flange and a noninvasive, flexible, pliable sheet with a central aperture for closing a sucking chest wound of a patient, while providing a possible path for discharging air, body fluids or any combination thereof from the pleural space of a patient. A generally flat, one-way check valve for allowing air discharge is located in the tubular base. A protective, tubular cover comprises a screening means and is used for protecting the check valve from foreign debris while allowing exit of air, body fluids or any combination thereof from the check valve and enabling visual monitoring of fluid levels within the device.

Abstract: A reservoir for use in an extracorporeal blood circuit including a rigid shell forming an enclosed reservoir. A filter unit divides the reservoir into an inlet chamber and outlet chamber. Cardiotomy blood filtering and defoaming means and venous blood filtering and defoaming means are located within the inlet chamber.

Abstract: A holder for a heat exchanger in a cardioplegia delivery system including dual couplers releasably engageable with the inlet and outlet ends of the heat exchanger. A one-way shut-off valve is associated with each coupler and opened to provide communication upon mounting of the heat exchanger. The valves automatically close upon release of the heat exchanger. A release member engages both couplers and is manually retractable to simultaneously open both couplers for release of both heat exchanger fittings for instantaneous release of the heat exchanger and a closing of the associated valves.

Abstract: An IV flow monitor is connected to a conventional IV bag via a self-contained puncture tube, and includes a liquid reservoir at the top, which allows the liquid to transfer through a transfer tube and then through a calibrated orifice tube into an orifice chamber, from which the liquid falls through an exit tube connected to a patient or other IV equipment. A manometer tube is connected between the liquid reservoir and the orifice chamber and is aligned with a measurement scale fixed to a backing plate upon which the apparatus is mounted. The pressure drop across the calibrated orifice tube produces a standing column of liquid in the manometer tube and principles of fluid flow allow the rate of flow through the apparatus to be read from the scale. An air trap chamber in an upper portion of the orifice chamber and hydrophobic gas membranes provide safety features that prevent air from being entrained in the liquid flowing through the exit tube to the patient.

Abstract: The proposed device comprises an outer tube having a central canal and perforations at its one end, a stylet fitted in the central canal of the outer tube, an inner tube, which is in fact a non-return valve and with its one end tightly connected to the outer tube and with its opposite end stretched over the stylet with a possibility of slipping off the latter and getting everted. The device has a receptacle for collecting the pleural fluid, tightly connected to the outer tube and the inner tube, and a retainer for fixing the device in position.

Abstract: An apparatus for controllably intermixing two or more components in a sterile, closed environment to produce a flowable substance and then for expelling the flowable substance from the apparatus at a precisely contolled rate. The apparatus is particularly useful for medical applications and includes a dispenser portion with its own stored energy element provided in the form of an elastomeric membrane and a coupling mechanism for coupling a drug vial to the dispenser portion for controlled mixing a medicament contained within the drug vial with a diluent stored within the dispenser portion of the apparatus via a sterile pathway.

Abstract: A device for use in intravenous feeding comprises a reservoir of an intravenous fluid and an intravenous tube connected at one end to the reservoir, the tube being provided on an inner surface with a layer of a water-soluble biocompatible material visible through a wall of the tube. In use, an intravenous fluid is flushed through the tube or tube assembly until the water-soluble biocompatible layer dissolves and is no longer visible. Upon the dissolution of that layer into the intravenous fluid flowing through the tube assembly, a free end of the tube assembly is connected to a patient, while the tube assembly is maintained filled with the intravenous fluid.

Abstract: A system and method for connecting two fluid carrying tubes includes a first tube having a lumen therethrough and an open end, and a bubble elimination port proximate the open end and in fluid communication with the lumen, and a second tube having a lumen therethrough and an open end. The first and second tubes are connected in a first position, wherein the lumen of the first tube and the lumen of the second tube form a fluid-tight circuit and the bubble elimination port is open to the circuit, to eliminate any bubbles in the fluid circuit. The first and second tubes then are connected in a second position, wherein the lumen of the first tube and the lumen of the second tube form a continuous, fluid-tight circuit and the bubble elimination port is closed to the fluid circuit.

Abstract: An apparatus for controllably intermixing two or more components in a sterile, closed environment to produce a flowable substance and then for expelling the flowable substance from the apparatus at a precisely controlled rate. The apparatus is particularly useful for medical applications and includes a dispenser portion with its own stored energy element provided in the form of an elastomeric membrane and a coupling mechanism for coupling a drug vial to the dispenser portion for controlled mixing a medicament contained within the drug vial with a diluent stored within the dispenser portion of the apparatus via a sterile pathway.

Abstract: A device for use in controlling the intravenous drip comprises a cap and a dripping vessel. The cap is connected with a solution bottle of the intravenous drip by means of an upper connecting tube while the dripping vessel is in communication with a hypodermic needle by means of a lower connecting tube. The cap is provided thereon with a gas column having therein a gas duct in which a press rod is movably disposed. The gas in the upper connecting tube and the dripping vessel can be let out rapidly by means of the press rod.

Abstract: A resilient material pressurizing plunger for syringes or like containers in which the plunger construction is such that on the initial insertion into the syringe by a first inserting member, the plunger is distortable thus allowing the gas pressure generated by the plunger insertion to escape. The plunger is also capable of pressurizing the chamber when further insertion occurs by use of a second insertion member which prevents the distortion.

Abstract: Medical infusion apparatus comprises a housing in which a standard flexible liquid reservoir is disposed. A constant-force spring applies pressure to the reservoir to force liquid out of the reservoir and along a conduit to a patient. The spring is energized by the opening of a lid of the housing which permits replacement of the reservoir.The liquid flowing out of the reservoir passes through a molded conduit part which is configured so that it is positioned at a predetermined location with respect to a flow monitor. The flow monitor injects a pulse of heat, and detects the rate at which the heat pulse travels along the conduit. A microprocessor uses the sensed flow rate to control a stepper motor which regulates fluid flow by squeezing the conduit via a spring-biased member. The apparatus has active and standby modes in which the monitor is operated respectively more and less frequently.

Abstract: A device for detecting air in large bore thin walled transparent tubing, including a body providing accommodation for the tubing; an LED in a passage body for transmitting light energy towards the tubing; a phototransistor mounted in an orthogonally extending passage for receiving light transmitted by LED and modified by changes in the constituency of fluid passing through tubing; and an optical spacer in the form of a slotted collar of material optically matched to the material of tubing occupying space between LED and the tubing and phototransistor.

Abstract: Apparatus and method for detecting the presence of friable atheromatous deposits in or near the aortic arch of a patient. Fluid aspirated from the aorta in the region of the inner curvature of the transverse arch and the descending aorta through a cannula attached to a handle is drawn by suction through a filter in the handle, and any particulate is trapped for determining the presence of atherosclerotic plaque. A manually operated valve in the handle controls the suction and an elastomeric check valve prevents fluid backflow.

Abstract: A plaster which comprises a gas check valve being inserted in an aperture and which, on the side facing the skin, is provided with a carrier being coated with a pressure sensitive adhesive, makes the emergency treatment of open thorax injuries possible.

Abstract: A blood aspiration assembly has an aspirator receiver. The receiver has a housing with a rigid casing and a resilient plug, and a liquid flow chamber. The chamber has an offset lower wall surface, to create turbulence to remove air bubbles during initial set up. The offset wall can be elevated with an intermediate part of larger cross section to accommodate the blunt needle. The plug has a slit or perforation to allow passage of a blunt needle therethrough. The plug can have two parts of different compliance, with aligned slits or perforations. The blunt needle tip can be rounded or flat, with a side opening for the needle bore. The contour of the needle tip and the design of the plug are correlated such that the working force required to penetrate the needle tip into the plug perforation is considerably less than the force required for said needle tip to penetrate normal intact human skin of the hands or arms. A stop prevents the needle from contacting the aspiration chamber wall.

Abstract: A one-way valve for use in the emergency closing of an open thoracic wound to prevent inflow of air into the thoracic cavity but permitting one-way outlet flow of air and liquid from the cavity thus preventing pressure build up within the thoracic cavity.

Abstract: A blood reservoir serves to suppress generation of air bubbles in blood in an extracorporeal blood circulation circuit. The blood reservoir includes a blood storage chamber for temporarily storing the blood, the blood storage chamber having blood inlet and outlet ports, and a fluid-permeable blood spouting inhibitor disposed over the blood inlet port. Since the blood flows into the blood storage chamber through the blood spouting inhibitor, the blood is prevented from being spouted into the blood reservoir, so that air bubbles are prevented from being generated in the blood.

Abstract: The apparatus for priming a hypodermic needle with hazardous fluid and for retaining the hazardous fluid expelled from the needle in purging air from the needle includes a hypodermic needle and a tubular sheath member with a distal fluid containment chamber. The proximal end of the needle is adapted to be connected to a syringe or I.V. tubing, and is preferably removably mounted in the base portion of the sheath. The containment chamber includes a sealing membrane through which the needle extends, and a vent with a hydrophobic filter is disposed in the distal end of the containment chamber for venting air. A deflector shield is also provided within the containment chamber between the hydrophobic filter at the vent opening and the hypodermic needle for deflecting the hazardous fluid expelled from the distal end of the needle.

Abstract: An apparatus for controllably intermixing two or more components in a sterile, closed environment to produce a flowable substance and then for expelling the flowable substance from the apparatus at a precisely controlled rate. The apparatus is particularly useful for medical applications and includes a dispenser portion with its own stored energy element provided in the form of an elastomeric membrane and a coupling mechanism for coupling a drug vial to the dispenser portion for controlled mixing a medicament contained within the drug vial with a diluent stored within the dispenser portion of the apparatus via a sterile pathway.

Abstract: Liquid infusion apparatus comprises a drip chamber in which an outlet tube projecting into the chamber is enclosed by a cap including a side wall enclosing the upper portion of the outlet tube. The cap side wall has an inner diameter which is substantially largre than the outer diameter of the outlet tube, to thereby define a large passageway at the entrance of the outlet tube. This passageway substantially reduces the flow velocity of the liquid at its interface with the air in the drip chamber, and thereby substantially eliminates the possibility of air bubbles being trapped within the liquid fed through the outlet tube under high rates of liquid flow and under exceptionally rough handling conditions, such as when the transfusion is being administered while the patient is in a helicopter or in a land vehicle.

Abstract: An air detector according to the present invention utilizes a unitary type sensor for detecting air bubbles or columns in an infusion solution flowing through a tube. Because of a unique design for a tube-receiving groove and a cooperating abutting member, the difficulty in loading a tube heretofore encountered with the use of unitary type sensor is obviated. Thus, the tube can be loaded in the air detector easily with good reliability.

Abstract: A blood reservoir device comprising a generally flexible blood collection chamber having an inlet portion and a main portion. The inlet portion is preferably sized and configured such that blood entering the inlet portion will avoid turbulence and will undergo generally laminar flow through the inlet portion, into the main portion of the chamber. A vent tube is provided for venting coalesced or collected gas bubbles from the top edge of the chamber. Additionally, one or more filter elements may be positioned within the chamber to further facilitate removal of air bubbles from blood passing through the chamber.

Abstract: The Rapid Infusion Device is a mechanical pumping system for the rapid delivery of filtered, bubble free, warmed volume to a patient suffering from acute hypovolemia. The principle of operation is one of overcoming resistance mechanically, The flow of fluids is totally regulated by the resistance encountered at the smallest tubing orifice along the infusion pathway. The RID components, assembled as a system, provide the capability for the rapid infusion of filtered, bubble free, and warm volume. The word volume is used to describe the fluid delivered by the device as any desired fluid may be delivered by the device. The RID is composed of two systems, i.e., durable permanent equipment and a disposable unit for one time use. Durable equipment consists of a roller pump, its controls, a permanently mounted heating element and its controls, and a mounting bracket to attach the heating element to the housing of the roller pump. The disposable unit is made of molded plastic cast in two halves.

Abstract: A bubble detection system for use in a fluid delivery line leading to a patient for automatic delivery of a fluid. The system monitors a parameter indicative of compressibility of the fluid being delivered and compares that monitored parameter with a known value of the same parameter using a relatively incompressible fluid. If the fluid being delivered is more compressible by a predetermined amount, the system recognizes the existence of a bubble and stops the further movement of fluid toward the patient and reduces the pressure in the fluid delivery line upstream of the bubble to prevent the bubble from progressing further toward the patient. The parameter may include pressure in the fluid delivery line, force required to deliver the fluid or motor current in the event an electric motor is used in delivering the fluid.

Abstract: An in-line fluid conduit condition analyzer which includes a chamber placed in the conduit flow path and having one wall forming a piezoceramic bender that varies the chamber volume (or pressure) according to a predetermined waveform or noise spectrum and an associated piezoceramic pressure or displacement sensor. The time derivative of the displacement or the pressure are analyzed under computer control to identify conduit abnormalities. In particular application to intravenous fluid administration to patients, the system is capable of distinguishing a number of abnormalities including cathether obstruction, catheter needle out of the vein, catheter needle into the vein, as well as fluid bubble presence or conduit disconnection.

Abstract: An infusion device includes an infusion pump for delivering a liquid through an infusion conduit from a separate source of the liquid into a patient, a bubble detector for detecting the presence of an air bubble in the infusion conduit, and control circuitry responsive to the bubble detector for determining if the size of the air bubble is unacceptable. The control circuitry is configured to determine if during the time the air bubble is detected it advances a distance indicative of the unacceptable size, one embodiment counting the steps of a linear peristaltic infusion pump for that purpose.

Abstract: Blood is stored under refrigeration at a temperature of about 4.degree. C. When it is utilized on a relatively rapid basis within a surgical theater it is transported by tubing through a blood warming apparatus which, while warming the blood, causes an outgasing of entrained air. This air is trapped in an air trap receptacle having a drip chamber within which a gas-blood interface is developed. To assure that the capacity of the trap is not exceeded, an improved technique of gas removal and interface level setting is provided wherein access is achieved essentially through the entrance region of the gas trap receptacle.

Abstract: In a blood reservoir comprising a container casing defining a space for accommodating blood, the casing having a generally rectangular contour defining a pair of top and bottom sides and a pair of laterally opposed sides, provided that the casing assumes a vertically upright attitude, an inlet port is disposed in one lateral side of the casing for introducing blood into the space, an outlet port is disposed in the bottom side of the casing for discharging blood from the space, and a vent port disposed in the top side of the casing in fluid communication with the space. In another form, a partition separates the space into upper and lower compartments, and apertures are formed in the partition for allowing partial fluid communication between the compartments. The inlet port and the vent port are in communication with the upper compartment, and the outlet port is in communication with the lower compartment.

Abstract: An over-the-needle I.V. catheter is depicted for attachment to an I.V. fluid supply. This product is primed prior to puncture of a patient's blood vessel. This product includes a catheter hub with an attached flexible catheter having its forward end tapered to provide penetration capability. This hub has a connection to I.V. fluid supply. The catheter is sized to accept a needle which in mounted condition has its sharpened tip extending from the entering end of the catheter. Venting is provided. The needle when and as withdrawn leaves a hole in a seal which in this product utilizes a resilient disc which may or may not be slit. Two washers are employed to assist in sealing of this needle withdrawal hole. A threaded cap is rotated just prior to use to bring this resilient disc under compression. Alternate means is provided by a bayonet-type of force actuation and lock.

Abstract: A device for administering solid or semisolid preparations in an organism subcutaneously. The equipment comprises a barrel having a nozzle for attachment of a hollow needle, a plunger slidably arranged in the barrel and is used in combination with a guide member adapted to be snugly accommodated within the lumen of the barrel. The solid preparations are generally housed in the guide member and/or needle and forced into the body subcutaneously through the needle.

Abstract: An irrigation system for arthroscopy of a joint includes a high pressure bleed valve assembly and a monitor check valve assembly to control fluid communication to the joint via suitable tubing for the purposes of directing fluid inflow, joint fluid pressure monitoring, and to assist with connection of the tubing for an arthroscope and cannula inserted into the joint. The high pressure bleed valve assembly is pressure responsive to direct fluid to the joint via alternative paths.

Abstract: A device for use in the sampling or infusion of liquids from or to the human or animal body having a first connecting means (8) for connection to a cannula, a second connecting means (13) for connection to a source or drain of liquid and valve means (4,9) operable to open or close a flow path therebetween, the arrangement being such that in a closed condition of the valve means each of the connecting means is connected to a respective chamber (6, 7), each chamber having a respective venting means (20, 21) allowing the escape of air therefrom while preventing the escape of liquid and such that in an open condition of the valve means a flow path is established from one connecting means to the other through at least one of the chambers. The device allows connection to be made without spillage and removes air from the liquid.

Abstract: A Y-joint eliminates air space between an injection member and an injection uct by inducing flow from the intake duct towards the injection membrane. The induced flow may be generated by a deflection duct or a bypass duct. In either case, fluid infusion solution is induced to flow in a direction opposite the normal flow of the discharge duct.

Abstract: A device for administering liquid in a device for the parenteral administration of liquid, comprising a pump which conveys the liquid through an elastic tube to the patient, the entry of air into the tube is prevented by the provision of a valve (20) in the tube downstream of the pump. This valve opens in the patient's direction under a pressure of such magnitude that the pressure inside the tube upstream of the valve is at least approximately as great as the external air pressure. The check valve provided may be used together with a pump as well as under mere gravity feeding.

Abstract: A modular, power augmented medical infusion apparatus to provide rapid transfusion of relatively large quantities of blood, blood components, colloid, and fluids to patients. All components of the infuser that contact blood are sterlie, disposable, and easily assembled. Disassembled or partially assembled the components are also easily transportable. The major components comprise a pair of filtered cardiotomy reservoirs, an air embolus sensor, a modular double roller pump, a heat exchanger, a bubble trap-filter and disposable fluid conduits. The bubble trap-filter is located in the distal most location of the recirculating loop just upstream of the Y-connector to the patient and the air sensor just downstream of the cardiotomy reservoir in the proximal location of the recirculating loop.

Abstract: A venous reservoir for use in cardiotomy bypasses comprising a flexible, variable capacity bag having a vertical seal positioned between the outlets and inlets along the lower seal line. The vertical seal line is positioned off-center such that the velocity of blood decreases as it passes the top of said seal line and towards the lower outlet to increase the removal of bubbles from the blood. All ports serving the reservoir are constructed without internal projections into the reservoir to decrease the possibility of thrombosis. The upper and lower edges of the reservoir are looped to receive horizontal rods slidably attached to a vertical support. Adjustment of the distance between the rods varies the volume possible within the reservoir.

Abstract: A method of reducing the adhesion of bubbles to the surfaces of a medical administration set with which a parenteral liquid comes in contact prior to its introduction into a patient by treating the surfaces of the medical administration set with which the liquid comes in contact to increase the critical surface tension thereof prior to contacting the surfaces of the medical administration set with the liquid, preferably by radiation grafting with a solution of a monofunctional monomer compound.

Abstract: An air-in-line detector for use with an IV administration system comprises a light emitter positioned relative to a plurality of light sensors for receiving an IV tube therebetween. A comparator is connected with the light sensors to determine the relative intensity of light respectively incident on each sensor. Means connected with the comparator generates signals in accordance with the relative intensities to indicate whether an IV tube is present and, if so, whether there is fluid or air in the tube.

Abstract: Air entrained in a pumped liquid is released from a pumping chamber operated by a single piston and having an outlet passage controlled by a back-seating valve biased closed by a spring, when the piston near the end of its compression stroke causes positive mechanical engagement to open the outlet valve.

Abstract: This device relates to an improvement on mechanical enhancement of the pumping action of the human heart, which is achieved by an external venting source, such as a pump joined to an instrument insertable into a patient's heart or aorta and serving to vent excessive gases from the heart, thereby improving brain and lung functions in a closed-loop fashion, by improving the pumping ability of the human heart.

Abstract: A vascular catheter for cannulating arterial or venous vessels, for example in the fermoral region, or the vena cava and/or the right auricle of the heart, comprises a flexible tube having blood passage orifices in the nature of holes at its anterior and insertion end to be inserted in the vessel or the auricle, which tube is directly or indirectly connectable at its other open end to a conduit or appliance. A piston-like closure member is movable to and fro in the tube in lengthwise direction thereof, such that it covers and thereby closes at least same of the blood passsage orifices in one position in the tube and clears these orifices in other positions. Preferably, the closure member is so fashioned that in its closure position, it covers all blood passage orifices in the insertion end of the cathether tube.

Abstract: A central venous pressure catheter has a long flexible tube containing at least three channels or lumens. Toward the tip or distal end of the catheter are three ports in the wall of the tube each providing access to one of the lumens, respectively. An inflatable balloon, formed about the tube is located between a distal and a proximal of the ports and a balloon-inflating port lies within the balloon. The balloon is spaced away from the distal port by about 8 centimeters so that when the balloon is located in an upper region of the superior cava vein of an upright-positioned patient undergoing surgery of the head or neck, the balloon may be inflated just enough to raise the blood pressure at the site of the surgery to about equal that of the ambient atmosphere. There is thus no bleeding from cut veins and neither is there any tendency for cut veins to aspirate leading to an air induced embolism.

Abstract: A pressure sensor comprising a main body having an inlet connectable to a source of liquid under pressure, an outlet, a passage extending through the main body from the inlet to the outlet and a surface outside of the passage. A flexible diaphragm confronts the surface and is coupled to the main body to at least partially define a sensing chamber. The main body has a port extending from the passage to the sensing chamber to provide communication between liquid under pressure in the passage and the sensing chamber. The port has a transverse cross section with at least one dimension which is no greater than about 0.060 inch.

Abstract: A method for preventing the introduction of air into the vascular system of a patient during intravenous or intra-arterial procedures, as well as for preventing the reflux of fluids into the body of a patient. Also, novel fluid directing means and catheters which include integral or attached fluid flow control means for use in this method.

Abstract: First and second spaced apart optical emitter-receiving pairs are located along a liquid carrying conduit. A regulator circuit is coupled to each emitter-receiver pair to control the operation of that pair inside a maximum response range regardless of the transparency of the liquid. The regulator circuit is so arranged as to supply the emitter with a voltage which is a function of the difference between a voltage supplied by the receiver portion of an optical-receiver pair and a reference voltage. A differential circuit produces a differential signal representing the difference between the signals produced by the receiver portions of the optical emitter-receiver pairs and a comparator circuit is connected to the differential circuit in order to generate an alarm signal as a function of the differential signal. The detector is particularly useful as an air bubble detector in a transfusion or perfusion system, and can also provide a container-empty alarm in such systems.