Abbott Laboratories Corporation

Hospira, Inc.

Peter A Holst

Rudolph J Maske

David A Krajewski

Giovanni Pastrone

Robert G Poli

Thomas L Smith

V Stanton Thomas

Marc R Bunyard

Frank S Mo

Anthony C Yung

Michael E Kelly

A pump used to infuse a fluid into a patient is controlled in accordance with an algorithm that enables a microprocessor to monitor and adjust each pump cycle to compensate for a differential pressure between the pump's inlet and outlet. The algorithm defines a fluid delivery protocol that is applied in controlling the operation of the pump to achieve a desired rate, volume, and timing of the fluid infusion. Fluid is delivered by the pump when a plunger compresses an elastomeric membrane overlying a fluid chamber. Due to the small volume of the chamber, an incremental change in the plunger position before the delivery stroke produces a significant change in the delivery pressure. At the beginning of a pump cycle, the microprocessor determines the differential pressure between the inlet and outlet of the pump, and adjusts the plunger position before the delivery stroke to compensate for the differential pressure. A retraction of the plunger from the home position decreases the delivery pressure of the fluid, and an advancement of the plunger increases it. After the position of the plunger is adjusted to compensate for the differential pressure, the pump cycle proceeds. Following the plunger stroke, the outlet pressure is used to determine the actual volume of fluid delivered. The duration of the plunger stroke in the next pump cycle is adjusted to compensate for any volume delivery error produced by the differential pressure compensation.

Methods for compensating for pressure differences across valves in IV pumps

Method for compensating for pressure differences across valves in cassette type IV pump

A coupler for connecting a drive shaft to a driven member and accommodating a substantial misalignment between the drive shaft and the driven member, while minimizing audible noise and vibration. The coupling includes a hollow core nest element having a plurality of slots formed in one end, two substantially identical elongate body elements, and a plurality of spring elements. Each elongate body element has two ends, a first end being adapted to couple with either the drive shaft or the driven member, and a second end that includes a plurality of posts that engage the slots of the hollow core nest. An aperture in the hollow core nest is larger than the diameter of the elongate bodies, allowing for the components to move radially relative to each other to accommodate for any offset and misalignment between the longitudinal axes of the drive shaft and the driven member, while the spring elements ensure that the components positively contact one another to reduce audible noise that is otherwise produced by loose fitting components. In one embodiment, a spring element is integrally formed in the slots of the hollow core nest, such that the posts of the body elements are held in engagement with sides of the slots by the spring elements. This embodiment includes an end cap that prevents the posts from becoming disengaged from the slots. Another embodiment employs helical coil springs mounted externally around the hollow core nest.

Universal style coupling

A method and apparatus for driving a stepper motor such that when the motor is stepped, the velocity of the motor is substantially zero upon reaching a new stepped position, thereby eliminating overshoot and ringing, and the wasted energy associated with these effects. The method comprises energizing at least one of the stepper motor windings at a predetermined current level for a predetermined step time, wherein the current level is determined as a function of the step time and dynamic single-step response characteristics of the stepper motor and load so that the motor velocity is substantially zero when the adjacent stepped position is reached. At this point, the stepper motor windings that were energized to make the rotor of the motor move are de-energized, whereupon the rotor is held in place by the inherent detent torque of the stepper motor. Since the velocity of the motor is substantially zero when the adjacent stepped position is achieved, there is no overshoot, and thus ringing is eliminated.

Pseudo half-step motor drive method and apparatus

An IV pump actuates a disposable cassette having two parallel fluid paths that include first and second pumping chambers. The disposable cassette (12) has a housing(14) that includes a back portion (152) in which is defined a fluid path (60) between an inlet port (16) and an outlet port (18). An elastomeric membrane (150) is sealed between the back portion and a front portion (52). The elastomeric membrane is exposed through the front portion at a first pumping chamber (82), a second pumping chamber (84), inlet valves (70, 76), and outlet valves (86, 92). The inlet valves operate in a fully open mode, a fully closed mode, and a cracking mode. The cracking mode of the inlet valve occurs as the elastomeric membrane is initially forced further into the pumping chamber. If the pressure of the fluid in the pumping chamber exceeds a predetermined cracking pressure, the inlet valve is forced open so that the fluid flows from the pumping chamber back toward the inlet port. The inlet valve then fully closes and fluid flows through the outlet valve. Since fluid is forced alternatively from the first and second pumping chambers, the flow from the outlet port is substantially continuous. During the pumping stroke, operation of the inlet valves in the cracking mode compensates for variations in the proximal pressure. The outlet valves can also be operated in a cracking mode to compensate for variations in the pressure distal to the cassette.

Dual plunger cassette pump

A system and method for mounting a piezoelectric crystal and forming electrical connections to it in an air bubble sensor (10). Piezoelectric crystals (26, 54) are mounted against inner surfaces of two opposed cavities (16, 44) using a conductive epoxy. The conductive epoxy both adhesively secures the crystals in place and provides conductive paths to adjacent conductive pins (28, 30, 46, and 48). To mount one of the piezoelectric crystals, a drop of the conductive epoxy is placed on an inner planar surface of the cavity and the crystal is pushed into the conductive epoxy, forcing the conductive epoxy to flow from under the crystal and into contact with one of the conductive pins. The inner end of another conductive pin is bent over the crystal and a drop of the conductive epoxy is then placed on the outwardly facing surface of the piezoelectric crystal, electrically and mechanically coupling the end of the conductive pin that was bent over, to the outwardly facing surface of the crystal. One of the piezoelectric crystals is electrically excited at its resonant frequency, producing ultrasonic sound waves used to detect gaseous bubbles in a liquid flowing through an intravenous (IV) line disposed in a gap(42) formed between two upright supports (14, 40) in which the piezoelectric crystals are mounted. Bubbles in the line attenuate the ultrasonic signal received by the other piezoelectric crystal, reducing an output electrical signal that it produces in response.

Air bubble sensor with simplified mounting of piezo elements

A pressure sensor (10) that responds to stress introduced into a pair of cantilevered beams (42, 44), to sense pressures at two measurement points in a cassette (80). The pressure sensor includes a base (12) on which the cantilevered beams are mounted. The base also supports two S-shaped flat springs (34, 36) mounted in spaced-apart, parallel array. Pins (28, 29) supported by the S-shaped flat springs each contact a free end of a different one of the cantilevered beams. The pins transfer a force from an elastomeric membrane (86). This force is developed by fluid pressure acting on the elastomeric membrane in a fluid passage of a cassette used for pumping fluid. The pins transmit the force to the free ends of the cantilevered beams as an applied stress. Strain gauges (58, 60) that are fixed to the cantilevered beams each respond by producing a signal indicative of fluid pressure. This configuration senses a proximal and a distal fluid pressure in the cassette, with substantially zero displacement of the elastomeric membrane, thereby minimizing errors that would otherwise arise due to variations in the stiffness of the elastomeric membrane with displacement and providing a short response time to changes in pressure.

Sensor for measuring pressures in a cassette pump proximal and distal to

A identification system for a cassette pump wherein a plurality of different types of cassettes administer different types of drugs, and each type of cassette is characterized by a different type determinative indicia carried by the cassette, and the cassette pump includes a prime mover for actuating the plurality of different types of cassettes corresponding number of different operating modes, each operating mode being used with a corresponding different type of cassette, wherein the pump-cassette interface for receiving and actuating each of the different types of cassettes includes a sensor disposed at the pump-cassette interface, and when the sensor is engaged by the type determinative indicia of a cassette, the pump is able to identify the particular type cassette inserted into the pump, and initiate the operating mode of the pump associated with the specific type of cassette positioned at the pump-cassette interface.

Growing community of inventors

Castro Valley, CA, United States of America

Peter A Holst