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: 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.

Abstract: A calibration apparatus for use in calibrating a tissue stress sensor used in a blood pressure monitoring system. The calibration apparatus includes a calibration head which is adapted to be retained in close proximity to a tissue stress sensor. The calibration head includes means for heating the tissue stress sensor. A calibration system is also disclosed for calibrating a blood pressure monitoring system, the blood pressure monitoring system employing a stress sensor for generating an electric output signal representative of tissue stress data. The calibration system comprises a tissue stress sensor having a displaceable diaphragm and a sealed chamber. The chamber has a continuous wall defining an inner volume and an outer volume. The displaceable diaphragm comprises a portion of the continuous wall, whereby the displaceable diaphragm is responsive to a pressure differential between the inner chamber volume and the outer chamber volume.

Abstract: An air-in-line sensor is provided comprising an adapter for insertion in the fluid line and a sensor housing. The adapter is semi-compliant and includes convex-shaped acoustic coupling surfaces for engaging the straight and rigid transducer sensing walls of the housing. The convex surfaces of the adapter have a larger diameter than the distance between the housing sensing walls and an interference fit results. Due to this interference fit, the shape of the coupling surfaces, the varying thicknesses of the adapter walls and the difference in compliance of the materials of the adapter and the housing, a more uniform contact pressure profile is provided. The upper part of each sensing channel wall in the housing includes a ledge which wipes contaminants from the coupling surfaces of the adapter as it is inserted into the sensor channel of the housing.

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: An infrared detector receives infrared energy from the target and provides a detector signal based primarily on the difference between the infrared detector temperature and the temperature of the reference temperature area of the detector. A contact temperature measurement device provides a reference signal which is a function of the temperature of the reference temperature area of the detector. A processor receives the detector and reference signals and combines the two signals in a non-linear manner to result in a signal which is representative of the temperature of the target. The method of non-linearly combining includes the use of gain and offset terms which may be altered to a limited extent by a technician in the field with a blackbody calibration source. As a result of the recalibration, accurate target temperature measurements are continually provided.

Abstract: A sensor system has a two-housing arrangement, each housing of which contains a transducer. One housing includes the transmitter transducer and a flat engaging surface for pressing against the fluid line and deforming it. The other housing includes the receiver transducer mounted so that it is coupled to the bottom of a rectangular U-shaped channel for receiving the fluid line. A spring biases the flat surface of the first housing into contact with the fluid line and deforms the fluid line into the shape of the channel so that the fluid line fills the channel. The channel is shaped to force the fluid line into a general rectangular shape as it is pressed into the channel by the flat surface. Two walls of the deformed fluid line are oriented in a direction perpendicular to the flat engaging surface of the first housing and provide an opposing force to the flat surface.

Abstract: Automatic engagement of a lead screw with a lead screw drive mechanism. A plunger driver used to move the plunger of a syringe is connected to the screw drive mechanism. A first detector provides a plunger signal indicating the presence of a syringe plunger in the plunger driver and a second detector provides a thread engagement signal indicating engagement or disengagement of the lead screw drive mechanism with the lead screw. The thread engagement detector monitors movement of a rigid linkage at the screw drive mechanism which has a nonlinear characteristic curve. In the case where the plunger signal indicates the presence of a plunger and the thread engagement signal indicates engagement of the drive mechanism with the lead screw, the lead screw is rotated in a forward direction to remove the thread clearance.