US 5,303,698 A · Medical ventilator

Abstract

A medical ventilator is provided for providing continuous, closed-loop control of the pressure of gas within a patient's mouth or respiratory tract in accordance with any selected pressure input waveform. The medical ventilator comprises an adaptive, feedback controller which provides independent control of the inspiratory and expiratory branches of the ventilator, while continuously controlling mouth pressure. The digital coefficients of the controller are updated to adjust for variations in the resistance of the patient's respiratory tract resulting from the magnitude of flow of inspiratory gas into the tract and patient-to-patient differences. Pressure in the expiratory branch is controlled by controlling, through a pressure-regulating valve, the magnitude of back pressure applied to a diaphragm valve. A venturi provides a reference pressure for the pressure-regulating valve below that of the surrounding atmosphere to enable application of a negative back pressure to the diaphragm valve.

Claims59

Dependent claims

A medical ventilator for controlling the pressure of gas within a patient's respiratory tract, comprising:

(a) a source of inspiratory gas;
(b) an inspiratory conduit for directing the flow of said inspiratory gas from said source to said patient's mouth;
(c) inspiratory flow-control means for controlling the flow of said inspiratory gas within said inspiratory conduit;
(d) means for measuring the actual pressure of gas at a location such that the measurement is indicative of the actual pressure within said patient's respiratory tract;
(e) first comparator means for comparing said actual pressure with a desired pressure and for generating a first error signal indicative of the difference between said actual pressure and said desired pressure;
(f) processing means for processing said first error signal and for generating a first control-signal, in response to said first error signal, said processing means further comprising means for executing an inspiratory control function having a first time constant and for controlling said inspiratory flow-control means to cause said actual pressure to track said desired pressure;
and
(g) time-constant updating means for updating the value of said first time constant.

5 more elements

A medical ventilator for providing continuous, closed loop control of the pressure of gas within a patient's mouth, comprising:

(a) a source of inspiratory gas;
(b) inspiratory means for transmitting said inspiratory gas to the mouth of said patient;
(c) expiratory means for transmitting expiratory gas from the mouth of said patient;
(d) means for measuring the actual pressure of gas at a location such that the measurement is indicative of the actual pressure within said patient's mouth;
(e) comparator means for comparing said actual pressure with a desired pressure and for generating an error signal indicative of the difference between said actual pressure and said desired pressure;
(f) a control system for processing said error signal in accordance with a first set of processing parameters and for generating a first control signal for controlling said inspiratory means, and for processing said error signal in accordance with a second set of processing parameters and for generating a second control signal for controlling said expiratory means;
(g) evaluating means for evaluating the capacity of said first control signal and said inspiratory means, and the capacity of said second control signal and said expiratory means, for causing said actual pressure to track said desired pressure;
and
(h) selecting means for selecting, on the basis of said evaluating, either said first control signal and said inspiratory means, or said second control signal and said expiratory means, for controlling said actual pressure.

6 more elements

A system for providing closed loop control of the pressure of gas within a patient's mouth, comprising:

(a) an expiratory conduit for directing the flow of expiratory gas from said mouth;
(b) a diaphragm valve for controlling the pressure of said expiratory gas within said expiratory conduit;
(c) pressure means for applying back pressure to said diaphragm valve;
(d) means for measuring the actual pressure of gas at a location such that the measurement is indicative of the actual pressure within said mouth;
(e) first comparator means for comparing said actual pressure with a desired pressure and for generating a first error signal indicative of the difference between said actual pressure and said desired pressure;
(f) first processing means for processing said first error signal in accordance with a first set of processing parameters and for generating a first control signal;
(g) means for measuring the actual back pressure applied to said diaphragm valve;
(h) second comparator means for comparing the magnitude of said first control signal with said actual back pressure and for generating a second error signal indicative of the difference between said actual back pressure and the magnitude of said first control signal;
and
(i) second processing means for processing said second error signal in accordance with a second set of processing parameters and for generating a second control signal for controlling said pressure means such that said actual pressure of gas within said mouth tracks said desired pressure.

7 more elements

Dependencies are inferred from the claim text.

Medical ventilator

Life of this patent

Medical ventilator

Life of this patent

Abstract

Claims59