Bear Medical Systems, Inc.

Bourns Medical Systems, Inc.

Raymond A Ellestad

Harold U Bartels

Finn Sveen

Charles M Gropper

A pressure-limited, time-cycled pulmonary ventilator includes a pressurized gas system that supplies respiratory gas to a patient at a selected inspiratory flow rate; an exhalation valve that (a) opens an expiratory flow path in response to the elapsing of a selected inspiratory time period, and (b) maintains a selected proximal pressure limit during the inspiratory time period; and a volume-cycle override system that actuates the exhalation valve so as to open the expiratory flow path if the patient's tidal volume reaches or exceeds a selected volume limit during the inspiratory time period. The volume-cycle override system includes a flow sensor that outputs an inhalation flow rate signal. The flow rate signal is integrated to derive a measured tidal volume signal. An operator control produces a volume limit signal, indicating a selected volume limit, that is compared with the measured tidal volume signal to yield a difference signal. The exhalation valve opens the expiratory flow path in response to the difference signal having a value indicating that the measured tidal volume is equal to or greater than the selected volume limit, as long as the proximal pressure exceeds a selectable reference pressure. An exhalation control system provides a first reference pressure at the beginning of the inspiratory time period, and a second reference pressure at the end of the inspiratory time period, or when the difference signal indicates that the measured tidal volume is equal to or greater than the selected volume limit, whichever first occurs.

Pressure-limited, time-cycled pulmonary ventilation with volume-cycle

A directional sensor for the detection of a very feeble effort to breathe on the part of a patient whose breathing needs are under the influence and control of a mechanical ventilator. A self-heated thermistor assembly is mounted in a small diameter sensor tube. A diaphragm and chamber arrangement provides a low volume flow of air in the sensor tube past the thermistor assembly at a high velocity, so that a very small effort to breathe will draw a limited volume of air past the thermistor assembly at a high velocity, causing rapid cooling. The air will flow past the thermistor assembly in a first direction in response to an inhalation effort, and in a second direction in response to an exhalation effort. A heating element is arranged in the tube so that a first temperature-related voltage change is produced across the thermistor assembly when air flow is in the first direction, and a second such temperature-related voltage change is produced when air flow is in the second direction. The first voltage change resulting across the thermistor assembly is utilized to signal a patient effort to inhale and to command the ventilator to furnish an appropriate response, while the second voltage change, signaling an exhalation effort, is used to block such a response.

Directional thermistor assist sensing

A system for sequentially providing a volume of gas containing a high frequency oscillation to a proximal airway. In a preferred embodiment a control means periodically drives in synchronism both inhalation and exhalation means into an inspiratory phase of an oscillatory cycle and then into an expiratory phase of the oscillatory cycle. The inhalation means during the inspiratory phase delivers a volume of fresh gas to the proximal airway of a patient, and during the expiratory phase refills itself from a source of low pressure gas while simultaneously blocking therefrom expired gas from the proximal airway. The exhalation means during the inspiratory phase vents to atmosphere expired gas withdrawn from the proximal airway during the previous expiratory phase and simultaneously blocks therefrom fresh gas from said inhalation means and during the expiratory phase extracts the expired volume of gas from the proximal airway.

High frequency breath pump

A sensor for the detection of a very feeble effort to breathe on the part of a patient whose breathing needs are under the influence and control of a mechanical ventilator. A self-heated thermistor is mounted in a small diameter sensor tube. A diaphragm and chamber arrangement limits the volume of air that flows in the sensor tube past the self-heated thermistor. The self-heated thermistor is mounted in the center of the small diameter sensor tube so that a low volume flow rate of fluid will cause a relatively large amount of cooling. Thus a very small effort to breathe will draw a limited volume of fluid past the thermistor at a high velocity, causing rapid cooling. A voltage change resulting across the thermistor is utilized to signal a patient effort to breathe and to command the ventilator to furnish an assisted breath where appropriate.

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Rialto, CA, United States of America

Raymond A Ellestad