US 6,390,091 B1 · Method and apparatus for controlling a medical ventilator

Abstract

An open- or closed-loop method and corresponding medical ventilator for providing breathing gas to a patient such that the patient exerts a desired work of breathing during pressure support ventilation, and such that the work of breathing of the patient is monitored and the pressure and/or flow rate of the breathing gas provided to the patient is controlled throughout the inspiratory phase to provide a pressure support ventilation level that provides the desired work of breathing in the patient. The medical ventilator includes at least a pressure sensor and a flow rate sensor, disposed in a functionally open ventilator conduit in fluid communication with the lungs of the patient, electrically coupled to a microprocessor to monitor the average respiratory muscle pressure of the patient and to predict the patient work of breathing as a function of the current value of the average respiratory muscle pressure of the patient, to detect when the patient work of breathing is not within a predetermined work of breathing range, and to generate a response signal thereof. Further, the medical ventilator has a driver circuit electrically coupled to the microprocessor and to an actuator of a pneumatic system which, responsive to the response signal, may adjust the selected pressure support ventilation level of the breathing gas provided to the patient by the ventilator until a pressure support ventilation level is reached such that the patient work of breathing is within the predetermined work of breathing range.

Claims45

Dependent claims

A medical ventilator for providing pressure support ventilation to a patient, the medical ventilator in fluid communication with a gas source of one or ignore breathing gases and in flow communication with a functionally open ventilator flow conduit having a patient breathing attachment in fluid communication with the patient, the medical ventilator comprising:

a) pressure sensing means disposed within the ventilator conduit for sensing the pressure of the gas within the ventilator conduit;
b) flow rate measuring means disposed within the ventilator conduit for measuring the flow rate of the gas within the ventilator conduit;
c) monitoring means, connected to the pressure sensing means and the flow rate measuring means, programmed for:
a) monitoring a patient work of breathing, and b) determining a selected pressure support ventilation level to maintain the patient work of breathing within a predetermined work of breathing range;
and
d) gas delivery means for controlling a supply of the gas so that the gas is delivered to the patient at the selected pressure support ventilation level.

3 more elements

A method of providing pressure support ventilation to a patient supplied with a breathing gas from a medical ventilator having a selectable pressure support ventilation level, the gas being received into the medical ventilator from a gas source of one or more breathing gases, and the gas exiting the medical ventilator being in flow communication with a functionally open ventilator flow conduit having a patient breathing attachment in fluid communication with the patient, wherein a supply of the gas is controlled by the medical ventilator, the method comprising the steps of:

a) delivering the breathing gas from the ventilator to the patient breathing attachment at a selected pressure support ventilation level;
b) sensing the pressure of the breathing gas within the ventilator conduit and generating a pressure signal representative of that pressure;
c) measuring the flow rate of the breathing gas within the ventilator conduit and generating a flow signal representative of that flow rate;
and
d) providing a program for:
i) processing the flow signal and the pressure signal to determine the patient work of breathing;
ii) monitoring the patient work of breathing;
and
iii) determining the pressure support ventilation level for which the patient work of breathing is maintained within a predetermined work of breathing range.

6 more elements

A medical ventilator for providing pressure support ventilation of a patient, the medical ventilator comprising:

a gas source of one or more breathing gases in flow communication with the medical ventilator;
a ventilator flow conduit in flow communication with the medical ventilator and in fluid communication with the patient;
a pneumatic system having at least one actuator for controlling a supply of the breathing gas so that a selected pressure support ventilation level of pressure support ventilation is provided to the patient;
a pressure sensor disposed in the ventilator flow conduit which senses the pressure of the breathing gas proximate the pressure sensor and which provides a pressure signal representative of that pressure;
a flow rate sensor disposed in the ventilator flow conduit which senses the flow rate of the breathing gas within the ventilator flow conduit and which provides a flow signal representative of that flow rate;
a microprocessor programmed for controlling the selected pressure support ventilation level of the ventilator, the microprocessor being electrically coupled to the output of the pressure sensor and flow rate sensor, wherein the microprocessor determines a work of breathing of the patient, compares the work of breathing to a predetermined work of breathing range, generates a response signal based on the comparison, and communicates the response signal to at least one of the actuators of the pneumatic system so that the selected pressure support ventilation level of the ventilator is adjusted to bring the work of breathing of the patient within the predetermined work of breathing range.

3 more elements

a) delivering the breathing gas from the ventilator to the patient breathing attachment at a selected pressure support ventilation level;
b) sensing the pressure of the breathing gas within the ventilator conduit and generating a pressure signal representative of that pressure;
c) measuring the flow rate of the breathing gas within the ventilator conduit and generating a flow signal representative of that flow rate;
d) processing the flow signal and the pressure signal to determine the patient work of breathing by:
i) extracting a measured tidal volume of the breathing gas from the flow signal;
ii) calculating a real-time respiratory muscle pressure according to:
Pmus(t)=Pao(t)−[(Vao(t)/CRS)−({dot over (V)}ao(t)×RRS)]−Baseline Pressure
wherein,
Pmus(t)=the real-time respiratory muscle pressure;
Pao(t)=the pressure sensed;
{dot over (V)}ao(t)=the flow rate sensed;
Vao(t)=the extracted tidal volume;
CRS=the measured predetermined compliance of the respiratory system;
RRS=the measured predetermined resistance of the respiratory system;
Baseline Pressure=the measured predetermined baseline pressure of the ventilator system;
and
t=time during the inspiration phase where the pressure and flow rate are sensed and/or measured;
iii) calculating an average respiratory muscle pressure for the inspiratory period of a single breath according to:
P ⁢ ⁢ mus avg ⁢ ⁢ ( t ) = ∫ 0 T i ⁢ ( P ⁢ ⁢ mus ⁢ ⁢ ( t ) ) ⁢ ⁢ ⅆ t ;
wherein:
Pmusavg(t)=the average respiratory muscle pressure of the patient during inhalation of a single breath;
t=0 is the beginning of inspiration by the patient 10;
and
Ti=is the end of inspiration of a single breath;
iv) calculating an average respiratory muscle pressure for the patient over a serial number of breaths according to:
P ⁢ ⁢ mus avgN ⁢ ⁢ ( t ) = 1 / N ⁢ [ ∑ breath = 1 N ⁢ ⁢ P ⁢ ⁢ mus avg ⁡ ( t ) ] .
wherein:
PmusavgN(t)=the average respiratory muscle pressure of the patient over a serial number of breaths;
and
N=the number of serial breaths;
and
v) determining the patient work of breathing from the calculated average respiratory muscle pressure (PmusavgN(t));
and
e) monitoring the patient work of breathing.

31 more elements

A medical ventilator for providing pressure support ventilation of a patient, the medical ventilator comprising:

a gas source of one or more breathing gases in flow communication with the medical ventilator;
a ventilator flow conduit in flow communication with the medical ventilator and in fluid communication with the patient;
a pneumatic system having at least one actuator for controlling a supply of the breathing gas so that a selected pressure support ventilation level of pressure support ventilation is provided to the patient;
a pressure sensor disposed in the ventilator flow conduit which provides a pressure signal representative of the pressure of the gas proximate the pressure sensor;
a flow rate sensor disposed in the ventilator flow conduit which provides a flow signal representative of the flow rate of the breathing gas within the ventilator flow conduit;
a microprocessor programed for controlling the selected pressure support ventilation level of the ventilator, the microprocessor being electrically coupled to the output of the pressure sensor and flow rate sensor, wherein the microprocessor:
a) extracts and stores a measured tidal volume of the breathing gas from the flow signal;
b) determines and stores a real-time respiratory muscle pressure (Pmus(t)) of the patient from the stored measured tidal volume, the stored inspiratory flow rate sensed, and the stored pressure sensed;
c) calculates an average respiratory muscle pressure for the inspiratory period of a single breath (Pmusavg(t)) from the stored real-time respiratory muscle pressure (Pmus(t));
d) calculates an average respiratory muscle pressure of the patient (PmusavgN(t)) from the stored Pmusavg(t) over a serial number of breaths;
e) determines a patient work of breathing (WOB) from the calculated average respiratory muscle pressure (PmusavgN(t));
f) compares the work of breathing to a predetermined work of breathing range;
g) generates a response signal based on the comparison;
and h) communicates the response signal to at least one of the actuators of the pneumatic system so that the selected pressure support ventilation level of the ventilator is adjusted to bring the work of breathing of the patient within the predetermined work of breathing range.

11 more elements

Dependencies are inferred from the claim text.

Method and apparatus for controlling a medical ventilator

Life of this patent

Method and apparatus for controlling a medical ventilator

Life of this patent

Abstract

Claims45