Abstract: A restrictor fitting is provided at the discharge side of an infusion pump to substantially reduce or eliminate the presence of undissolved gas such as air within the detection field of an air-in-line sensor. The restrictor fitting defines a flow orifice of reduced cross-sectional size disposed along an infusion line in close proximity with a pump discharge port, and at a position slightly downstream from the air-in-line sensor. The restrictor fitting maintains an infusion liquid under substantially constant pressure conditions, with minimal pressure drop across the sensor detection field, and thereby minimizes the occurrence of undissolved gas attributable to outgassing at that location. In addition, the flow orifice acts as a bubble trap to prevent backflow of gas bubbles to the sensor detection field.

Abstract: A non-invasive, fluid monitor engages an open resonator with a segment of fluid line. The fluid line is disposed such that it and the fluid within become a part of the dielectric loading on the resonator. The open resonator is a part of an oscillator circuit that changes frequency of oscillation in response to the dielectric loading on the resonator. A frequency discriminator monitors the frequency of the oscillator to detect an air bubble in the fluid line. In the case where the resonator comprises a microstrip line, the microstrip line is disposed in parallel to the segment of the fluid line and the length of the microstrip line is selected to be equal to or greater than the maximum length of air bubble permitted thus providing a volumetric air-in-line sensor. The output of the frequency discriminator is compared to a threshold to determine a frequency shift large enough to indicate the presence of an air bubble.

Abstract: A pressure waveform monitor for non-invasively monitoring the pressure waveform inside a vessel, such as an artery, includes a flexible diaphragm extended across an opening of a container containing a fluid. The flexible diaphragm is placed against tissue surrounding an artery such that arterial pressure causes a deflection in the diaphragm. A deflection in the diaphragm causes the fluid to be redistributed throughout the container which is effectively divided into an array of volume compartments. The relative volume distribution is determined through impedance plethysmography. The diaphragm is maintained in a calibrated position by maintaining the array of volume compartments at relatively unchanged volumes. When the relative volumes remain essentially unchanged, calibrated tonometry is possible. The pressure within the container is then used to determine the pulse waveform and the pressure within the artery.

Abstract: A fluid shut off valve for use in a parenteral fluid administration set includes a disk floating in a fluid chamber that shuts off fluid flow when the fluid in the chamber decreases below a certain level. The chamber includes a valve stem at its lower end that has both a valve seat and an alignment member with an alignment surface on the top end thereof for guiding the disk into proper seating on the valve seat. The valve seat and floating disk have complementary engagement surfaces for also guiding the disk into proper seating on the valve seat. In one embodiment, the alignment member includes fins located both on the valve stem and on the inside wall of the chamber. Because of the configuration of the alignment member, dislodgement of the disk from the valve seat is made easier.

Abstract: Bidirectional flow patterns are induced in a fluid supply line and the reverse flow resistance and the forward flow resistance are measured and compared. A measure of the resistance to flow is made by normalizing a sum of the entire pressure response about a pressure baseline according to the volume of fluid in the bidirectional flow pattern. In the event that the cannula is positioned near or against the vessel wall, the resulting relatively large negative pressure response can indicate the positional irregularity. In one embodiment, a time period of zero flow is included between the positive and negative flow volumes to permit the system to stabilize.

Abstract: An infusion system with an air-in-line sensor is provided with improved apparatus and method for quickly and easily clearing small quantities of undissolved gas such as air from the sensor detection field. The infusion system includes an infusion pump having control components responsive to the air-in-line sensor to activate an alarm and/or to cease pump operation when undissolved gas is detected. A "clear air" key or switch is provided on the pump for actuation by medical personnel to operate the pump in a manner delivering a small pulse of the infusion liquid to move a small detected quantity of gas past the air-in-line sensor. The system can be adapted for actuation of the "clear air" key up to a selected number of times, while monitoring and accumulating the total fluid quantity delivered to a patient.

Abstract: A fluid flow control system having a valve disposed in-line with a fluid conduit extending between a fluid container and a fluid receiver. The conduit and valve are designed to be used with a fluid infusion device such as a peristaltic pump. The valve is non-clamping and includes a rotatable member with an external handle for controlling the valve between flow and flow stop positions. The handle can be manually operated as well as automatically operated. Mounted to the infusion device is an automatic operating mechanism for cooperating with the pumping mechanism of the infusion device to control the position of the valve. In a disclosed embodiment, the operating mechanism is mounted to an access door of the pump which cannot be closed until the peristaltic mechanism is engaged with the tubing. When the door is closed, the operating mechanism automatically moves the valve to the flow position. When the access door is opened, the mechanism automatically moves the valve to the flow stop position.

Abstract: A compliant chamber is formed in a fluid line which connects a fluid supply to a fluid receiver. The compliant chamber is alternately in fluid communication with the upstream and downstream segments of the fluid line. When the chamber communicates with the upstream segment it receives and stores fluid at the head pressure. When the segment communicates with the downstream segment, a pressure equalization pulse occurs. A pressure sensor in the downstream segment measures the pressure equalization pulse which is proportional to the head pressure. Processing the equalization pulse with the downstream fluid system resistance, the compliance of the compliant chamber and the equilibrium pressure results in a determination of the head pressure. Comparing the head pressure to thresholds permits determination of an occlusion or empty fluid supply. Where a peristaltic pump is used, the chamber is formed between the end fingers of the pump.

Abstract: A pump mechanism using a drive motor having an external rotor. In one case, cams are mounted on the external surface of the rotor. Cam followers or peristaltic fingers engage the cams and move linearly in response to the rotational cam motion. The cam surfaces are rotated from adjacent cam surfaces to achieve a peristaltic effect through the peristaltic fingers sequentially pressing against the fluid tubing. In another case, the external surface of the rotor is threaded and elongated. A nut is mounted on the rotor and confined to travel in only a linear direction. A coupling arm is connected between the nut and a syringe plunger to force the plunger into the syringe barrel and thereby move the fluid.

Abstract: A valve for fluids employs two telescoping parts which cooperate with one another to block fluid flow when pulled partially apart and open a flow path therethrough when pushed together. A plunger component, having a central bore, a closed off end and perforated walls, is slidingly and sealingly received within the collar of the hollow valve body. When the plunger's closed end is pushed far enough into the valve body so as to expose the apertures, fluid is free to flow from within the valve body into the plunger component. When pulled apart so as to cause the perforations to be positioned within the confines of the collar, flow is blocked. An actuation mechanism integrated into a housing serves to automatically pull the valve's components apart to stop flow when its cover is swung open and conversely causes the two components to be pushed together to open flow when the cover is closed.

Abstract: A tissue contact stress sensing system incorporates a semiconductor assembly and a continuous diaphragm to noninvasively determine the intra-arterial blood pressure of a patient. The system comprises a continuous diaphragm placed against a patient's tissue which covers an underlying artery. The semiconductor assembly is placed in close proximity to and spaced apart from the diaphragm for directly irradiating the diaphragm with electromagnetic radiation and receiving a portion of the electromagnetic radiation which is reflected from the continuous diaphragm. The disclosed system also utilizes a technique for minimizing the system errors associated with temperature drift and aging of the sensor.

Abstract: A method, for use in a non-invasive blood pressure monitoring system, of determining optimum artery applanation. The system uses a stress sensor including a stress sensitive element for detecting stress of tissue overlying an artery of interest. The tissue stress sensor is placed in communication with tissue overlying the artery of interest and at least one electrical signal is obtained therefrom representing stress data across the length of the stress sensitive element. The data represents stress datum communicated to a preselected portion of the stress sensitive element. From the stress datum, various algorithms are used, singly or in combination, to provide the best measure of optimum applanation state. Intra-arterial blood pressure is then calculated using datum collected at the optimum applanation state. In addition, to the optimum applanation methods, a method is disclosed for determining which portion of the stress sensitive element is best suited for estimating intra-arterial blood pressure.

Abstract: A method, for use in a non-invasive blood pressure monitoring system, of determining which portion of a stress sensitive element of a tissue stress sensor is best located for detecting the stress of tissue overlying an artery of interest. The tissue stress sensor is placed in communication with tissue overlying the artery of interest and a plurality of electrical signals are obtained therefrom representing stress data across the length of the stress sensitive element. Each electrical signal represents stress datum communicated to a predetermined portion of the stress sensitive element. From the stress datum, a centroid of energy is computed and the centroid of energy is used to determine which portion of the stress sensitive element is best located for determining the blood pressure within the artery of interest. A second method is disclosed which uses the centroid of a tissue foundation flexibility function to determine the best location along the stress sensitive element for determining blood pressure.

Abstract: A method, for use in a non-invasive blood pressure monitoring system, of operating a tissue stress sensor at an off-optimum arterial applanation state. The system uses a stress sensor including a stress sensitive element for detecting stress of tissue overlying an artery of interest. The tissue stress sensor is placed in communication with tissue overlying the artery of interest and at least one electrical signal is obtained therefrom representing stress data across the length of the stress sensitive element. The data represents stress datum communicated to preselected portions of the stress sensitive element. From the stress datum, various techniques are used to determine the optimum applanation state and the actual applanation state. A waveform scaling factor function is created which compensates for the errors associated with operating the tissue stress sensor at an off-optimum applanation state.

Abstract: A non-invasive, in-line fluid monitor includes a segment of fluid line disposed such that it and the fluid within become a part of the dielectric loading on an energized electromagnetic sensor device. Perturbations of the dielectric loading on the sensor device are monitored to determine certain fluid properties, such as pressure, composition, and the presence of air. The fluid line segment disposed through the electromagnetic sensor may be compliant and thus changes size in response to fluid pressure, altering the volume of the fluid line segment tin the cavity and altering the dielectric loading on the cavity. In one embodiment, a resonant cavity is used to encompass the segment of fluid line and a processor is used to compare changes in the resonant characteristics of the cavity to predetermined data to determine the properties of the fluid.

Abstract: A medical valve assembly comprises a valve body having a fluid passage therethrough, a valve member, and an urging means disposed within the fluid passage. The valve member is adapted to seal against a sealing surface of the fluid passage and the urging means is adapted to urge the valve member against the sealing surface. The medical valve can be used without a needle thereby eliminating risks associated with needle stick injuries. In applications where it is expedient to use a needle (such as prepackage medications) the medical valve accommodates the use of a needle to administer medication. The urging means is disclosed in a first embodiment wherein it is formed integral with the head portion of the valve member. In an alternative embodiment, the urging means is separate from the head portion of the valve member and is comprised of a metallic spring element.

Abstract: An artery applanation actuator for use in a system for noninvasively determining the intra-arterial blood pressure of a user incorporates a fluid actuator to effect movement of a sensor. The movement of the sensor is effective for applanating an artery of interest and measuring the stress of the tissue overlaying the artery of interest. Alternative embodiments of the artery applanation actuator are presented wherein an electric motor is used to activate a rotating arm which has a sensor located thereon. The rotation of the arm causes the sensor to contact and press against the tissue overlying the artery of interest. The artery applanation actuator is presented having a protective sheath surrounding the sensor to protect the sensor against inadvertent contact.

Abstract: A syringe plunger position detection and alarm system continuously determines the position of a syringe plunger and provides near end of travel and end of travel alarms. Plunger movement is also monitored and if movement is less than a calculated amount, an alarm is provided. A variety of syringes of different sizes is usable. A potentiometer is mounted along the line of travel of the screw drive mechanism and a marker is mounted to extend from the screw mechanism to the potentiometer to force an internal contact in the potentiometer. The voltage provided by this internal contact is analyzed by the process to derive absolute and relative position of the plunger. The end of travel position of each plunger is stored in processor memory and from the operator input rate of infusion, the characteristic curve of the potentiometer also stored in memory, the plunger displacement of the syringe, and the time of the near end of travel alarm, the voltage of the near end of travel position is calculated.