Ivac Corporation

Heinz W Georgi

Robert Dwaine Butterfield

Wallace L Knute

Richard L Foreman

Oliver J Smith

The method and system for detecting occlusion in a fluid line upstream of a pump concerns a fluid pump with a pump cycle in which the upstream pressure of the fluid line is communicated to the downstream portion of the fluid line. A pressure sensor located downstream of the pump is capable of measuring a relatively large negative-going pressure in the fluid line. A signal is generated to indicate occlusion based upon detection of negative-going pressure.

Method and system for upstream occlusion detection

An electronic method and apparatus for automatically determining systolic and diastolic blood pressures and heart rate by accurately detecting, verifying and evaluating the full stream of korotkoff sounds produced as electrical signals from a microphone in a cuff occluding the brachial artery of a patient and the corresponding blood pressure pulse signals which accompany and are precursors to genuine korotkoff sound signals. Blood pressure is measured with the aid of a programmed data processor such as a microprocessor. Waveform analysis is first performed upon the incoming signal waveforms to initially separate true pressure pulses and korotkoff sound signals from a variety of artifact and noise signals and to provide digital pulse streams in memory correctly indicating proper pressure pulse and korotkoff sound occurrences in the time and blood pressure domains, with each pressure pulse proportional in amplitude to the amplitude of the corresponding detected precursor input pressure signal represented and each korotkoff pulse proportional to the negative slope amplitude of the corresponding detected korotkoff sound. The output pulse signal streams are then further analyzed by the digital processing subsystem and compared with each other to additionally remove any noise and artifact signals passed as otherwise misleading genuine signals, to modify and certify the resultant data as either reliable or suspect, to determine heart rate and the most probable values of systolic and diastolic blood pressure levels indicated by the pulse signal streams detected during the measurement cycle.

Electronic sphygmomanometer

An improved method and apparatus for parenteral administration of medical fluids, wherein a normally shut-off intravenous feeding tube is selectively opened at a frequency and open period duration automatically regulated by a digital control system to establish a fluid flow rate at any selected rate over a wide dynamic range. Measured and desired flow rates are converted to digital electrical signals and compared, the electrical difference being used to vary a control voltage which establishes the width of energizing pulses controlling a member for opening the feeding tube. The frequency of the energizing pulses is preferably a non-integral multiple of the desired drop flow rate and varies from a very high ratio, e.g. 15.5, at very low flow rates to a much smaller ratio, e.g. 2.5, at very high flow rates.

Method and apparatus for fluid flow control

An electronic method and apparatus for automatically determining systolic and diastolic blood pressure and heart rate by accurately detecting, verifying and evaluating the full stream of korotkoff sounds produced as electrical signals from a microphone in a cuff occluding the brachial artery of a patient. Waveform analysis is first performed upon the incoming signal waveforms by an analog prescreening subsystem to initially separate true korotkoff sound signals from a variety of artifact and noise signals and to provide an output pulse stream correctly indicating korotkoff sound occurrences in the time and blood pressure domain, with each pulse proportional in amplitude to the amplitude of the corresponding korotkoff sound represented. The output korotkoff sound pulse stream is then digitized by an analog to digital converter and further analyzed by a digital processing subsystem to additionally remove any noise and artifact signals passed as otherwise misleading quasi-korotkoff sound pulses by the prescreening subsystem, to modify and certify the resultant data as either reliable or suspect, to determine heart rate and the most probable values for systolic and diastolic blood pressure levels indicated by the signal stream detected during the measurement cycle.

A syringe pump operated by a stepping motor to repetitively fill and empty a syringe cartridge over a plurality of operational cycles of successive fill stroke and pump stroke periods. The motor is driven by drive pulses from a digital pulse generation and control system, the pulse frequency establishing a predetermined fixed rate of fill during the fill stroke and being preselected, in accordance with desired output flow rate, to establish the rate at which the syringe is emptied during the pump stroke. The drive pulse rate during a fill stroke exceeds the maximum pulse rate during a pump stroke and, in order to maintain a proportional relationship between the preselected pumping rate and the actual pumping rate over each complete cycle of successive fill and pump strokes, the drive pulse frequency during each pump stroke is automatically increased to compensate for the time lost during each fill stroke. This is accomplished by accelerating counting up of the electrical network defining each individual pump stroke drive pulse period for a time interval equal to a single fill stroke drive pulse period. A start-up subsystem insures proper cartridge installation prior to initiation of a pumping cycle. Appropriate alarms respond to improper operating conditions including leakage from the source during the pump stroke, empty bottle or insufficient flow during fill, air in the I.V. line, a stalled motor, lack of flow due to system component failure, or occurrence of a runaway high pumping rate.

Fluid flow control system

A digital system wherein a wide variety of different electromechanical output control devices, e.g., stepping motor pump or solenoid actuated I.V. tube pincher, is driven by electrical output pulses of varible frequency and pulse width from a digital pulse generation and control system, the frequency and pulse width of the output pulses being selected and controlled by the system to establish drop flow rates with digital precision over an extremely wide dynamic range. Pulse width is determined by the relative states of a pair of digital counters in a digital memory, frequency being determined by a high, preferably non-integral, multiple of the desired drop flow rate. The equivalent of negative pulse width in the digital memory can be effectively utilized to expand the effective dynamic range of the memory for specified types of electromechanical output devices. A start up subsystem temporarily presets the initial pulse rate and speeds up early regulation. Duty cycle limitation and visual output pulse width monitoring is also provided. Appropriate alarms also respond to a variety of out-of-limit conditions.

An electronic method and apparatus for measuring temperatures by means of a thermistor in one arm of an electrical bridge, bridge output being varied by the on and off duty cycle of a shunting impedance selectively switched into and out of the balancing arm of the bridge in accordance with the relative states of a counting display register and a cyclically scanned counting register, the display register state being altered by gated pulses, under the control of bridge output, to provide a digital indication of measured temperature. Bridges of both the nulling and non-nulling types are disclosed using either a dual ramp integrator or conventional detector acting upon bridge output to provide an impedance measurement subsystem independent of reference supply voltage and also enabling non-linear analog to digital conversion to compensate for a non-linear thermistor temperature vs. thermistor resistance characteristics, without sacrificing measurement sensitivity. Anticipation circuitry is provided for monitoring and correlating the display register pulses with the time vs. temperature response characteristic of the thermistor, to selectively alter bridge balance and display register state so as to provide an advance indication of the anticipated temperature at which the termistor will finally stabilize.

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Del Mar, CA, United States of America

Heinz W Georgi