# US 11,027,081 B2 · Method and systems for patient airway and leak flow estimation for non-invasive ventilation

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- Number: US 11,027,081 B2
- Document ID: US11027081B2
- Status: Granted
- Kind: B2
- Application number: 15/742,545
- Filed: 2016-07-06
- Published: 2018-07-19
- Granted: 2021-06-08
- Earliest claimed: 2015-07-07
- Assignees: Koninklijke Philips N.V.
- Applicants: Koninklijke Philips N.V.
- Inventors: Michael Anthony Borrello
- Web page: https://patentgrep.com/patent/US11027081B2

## CPC

- A61M 16/026: {specially adapted for predicting, e.g. for determining an information representative of a flow limitation during a ventilation cycle by using a root square technique or a regression analysis}
- A61M 11/00: Sprayers or atomisers specially adapted for therapeutic purposes (in general B05B; {aerosol containers B65D83/14})
- A61M 16/0003: {Accessories therefor, e.g. sensors, vibrators, negative pressure}
- A61M 16/0051: {with alarm devices}
- A61M 16/0057: {Pumps therefor}
- A61M 16/06: Respiratory or anaesthetic masks
- A61M 16/0875: {Connecting tubes}
- A61M 2016/0036: {in the breathing tube and used in both inspiratory and expiratory phase}
- A61M 2205/15: Detection of leaks
- A61M 2205/18: with alarm
- A61M 2205/3334: Measuring or controlling the flow rate
- A61M 2230/40: Respiratory characteristics
- A61M: DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY (introducing media into or onto the bodies of animals A61D7/00; means for inserting tampons A61F13/26; devices for administering food or medicines orally A61J; containers for collecting, storing or administering blood or medical fluids A61J1/05); DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY (surgery A61B; chemical aspects of surgical articles A61L); DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR {(Electrotherapy, e.g. producing anaesthesia by the use of alternating or intermittent currents A61N1/36021)}

## Abstract

A method for estimating patient airway flow in a non-invasive ventilator system. The method includes the steps of (i) determining an estimated gas flow at the proximal end of the tubing; (ii) determining a proximal pressure error value by subtracting the measured pressure at the proximal end of the tubing from the estimated pressure at the proximal end of the tubing; (iii) compensating for the determined proximal pressure estimate error value; (iv) compensating for an error in the estimated gas flow at the proximal end of the tubing by feeding the estimate back into a sum of accumulated flows; (v) determining an estimated gas flow leak; (vi) monitoring for a leak in the non-invasive ventilator system; (vii) determining a gas flow leak factor; (viii) adjusting the estimated gas flow leak; and (ix) compensating for bias in the patient airway flow.

## Claims

### Claim 1

A method for estimating patient airway flow in a non-invasive ventilator system, the method comprising the steps of:
providing a non-invasive ventilator system, the non-invasive ventilator system comprising tubing having a distal ventilator end and a proximal patient end;
obtaining a measurement of tubing compliance and a measurement of one or more parameters of a nonlinear leak flow model of the non-invasive ventilator system comprising leak flow resistance;
measuring, using a distal gas flow sensor of the non-invasive ventilator system, gas flow at the distal ventilator end of the tubing;
measuring, using a proximal pressure sensor of the non-invasive ventilator system, pressure at the proximal patient end of the tubing;
determining an estimated gas flow at the proximal patient end of the tubing, the estimated gas flow comprising the measurement of gas flow at the distal ventilator end of the tubing, the measurement of pressure at the proximal patient end of the tubing, the obtained measurement of tubing compliance, and the obtained measurement of the one or more parameters of the nonlinear the leak flow model comprising leak flow resistance;
determining a proximal pressure error value by subtracting the measured pressure at the proximal patient end of the tubing from an estimated pressure at the proximal patient end of the tubing;
compensating, using a compensator, for the determined proximal pressure estimate error value;
compensating for at least one error in the estimated gas flow at the proximal patient end of the tubing by feeding the estimated gas flow back into a sum of accumulated flows;
determining an estimated gas flow leak, the estimated gas flow leak comprising the estimated pressure at the proximal patient end of the tubing and the obtained measurement of the one or more parameters of the nonlinear leak flow model comprising the leak flow resistance;
monitoring for an unknown leak in the non-invasive ventilator system using a feedback controller to estimate a size of the unknown leak during ventilation;
determining, when the unknown leak is identified, a gas flow leak correcting factor comprising leak information from a previous breath;
adjusting, with the determined gas flow leak correcting factor, the estimated gas flow leak; and
compensating for bias in the patient airway flow.

### Claim 2 (depends on 1)

The method of claim 1, wherein the step of obtaining the measurement of the one or more parameters of the nonlinear leak flow model comprising the leak flow resistance comprises determining one or more calibration measurements during a calibration procedure prior to breath delivery.

### Claim 3 (depends on 1)

The method of claim 1, further comprising the step of comparing the gas flow leak correcting factor to a predetermined lower limit.

### Claim 4 (depends on 3)

The method of claim 3, wherein an alarm is triggered if the gas flow leak correcting factor is below the predetermined lower limit.

### Claim 5 (depends on 1)

The method of claim 1, further comprising the step of comparing the gas flow leak correcting factor to a predetermined upper limit.

### Claim 6 (depends on 5)

The method of claim 5, wherein an alarm is triggered if the gas flow leak correcting factor is above the predetermined upper limit.

### Claim 7 (depends on 1)

The method of claim 1, wherein the compensator is a proportional-integral compensator that utilizes the following equation:
Q
^
L
=
(
K
i
+
K
p
⁢
s
s
)
⁢
(
P
p
-
P
^
p
)
.

### Claim 8 (depends on 1)

The method of claim 1, further comprising the step of suspending estimation when the gas flow at the distal ventilator end of the tubing or the pressure at the proximal patient end of the tubing cannot be measured, wherein the step of suspending estimation comprises suspending the estimated gas flow or the estimated gas leak flow.

### Claim 9

A non-invasive ventilator system, comprising:
airway tubing comprising a distal ventilator end and a proximal patient end;
a distal gas flow sensor configured to measure gas flow at the distal ventilator end of the airway tubing, the distal gas flow sensor comprising a blower flow sensor;
a proximal pressure sensor configured to measure pressure at the proximal patient end of the airway tubing; and
a gas flow controller configured to supply a determined volume of gas to the distal ventilator end of the airway tubing, wherein the gas flow controller is configured to determine the supplied volume of gas by: (i) determining an estimated gas flow at the proximal patient end of the airway tubing, the estimated gas flow comprising a measurement of gas flow at the distal ventilator end of the airway tubing, a measurement of pressure at the proximal patient end of the airway tubing, a measurement of tubing compliance, and a measurement of one or more parameters of a nonlinear leak flow model comprising leak flow resistance; (ii) determining a proximal pressure error value by subtracting a measured pressure at the proximal patient end of the airway tubing from an estimated pressure at the proximal patient end of the airway tubing; (iii) compensating for the determined proximal pressure estimate error value; (iv) compensating for at least one error in the estimated gas flow at the proximal patient end of the airway tubing by feeding the estimated gas flow back into a sum of accumulated flows; (v) determining an estimated gas flow leak, the estimated gas flow leak comprising the estimated pressure at the proximal patient end of the airway tubing and the obtained measurement of one or more parameters of the nonlinear leak flow model comprising the leak flow resistance; (vi) monitoring for an unknown leak in the non-invasive ventilator system using a feedback controller to estimate a size of the unknown leak during ventilation; (vii) determining, when the unknown leak is identified, a gas flow leak correcting factor comprising leak information from a previous breath; (viii) adjusting, with the determined gas flow leak correcting factor, the estimated gas flow leak; and (ix) compensating for bias in the patient airway flow.

### Claim 10 (depends on 9)

The non-invasive ventilator system of claim 9, wherein the controller comprises a compensator configured to compensate for the determined proximal pressure estimate error value.

### Claim 11 (depends on 10)

The non-invasive ventilator system of claim 10, wherein the compensator is a proportional-integral compensator that utilizes the following equation:
Q
^
L
=
(
K
i
+
K
p
⁢
s
s
)
⁢
(
P
p
-
P
^
p
)
.

### Claim 12 (depends on 9)

The non-invasive ventilator system of claim 9, wherein the controller is further configured to obtain the measurement of tubing compliance and the measurement of one or more parameters of the nonlinear leak flow model during a calibration procedure or from a database.

### Claim 13 (depends on 9)

The non-invasive ventilator system of claim 9, wherein the controller is further configured to compare the gas flow leak correcting factor to a predetermined lower limit.

### Claim 14 (depends on 13)

The non-invasive ventilator system of claim 13, wherein the controller is further configured to trigger an alarm if the gas flow leak correcting factor is below the predetermined lower limit.

### Claim 15 (depends on 9)

The non-invasive ventilator system of claim 9, wherein the controller is further configured to compare the gas flow leak correcting factor to a predetermined upper limit.

### Claim 16 (depends on 15)

The non-invasive ventilator system of claim 15, wherein the controller is further configured to trigger an alarm if the gas flow leak correcting factor is above the predetermined upper limit.

### Claim 17 (depends on 9)

The non-invasive ventilator system of claim 9, wherein the controller is further configured to suspend at least one of the estimations comprising the estimated gas flow and the estimated gas leak flow when the gas flow at the distal ventilator end of the tubing or the pressure at the proximal patient end of the tubing cannot be measured.

### Claim 18 (depends on 17)

The non-invasive ventilator system of claim 17, wherein the controller is further configured to suspend at least one of the estimations comprising the estimated gas flow and the estimated gas leak flow when the controller determines that circuit model behavior has been compromised by one of a standby, circuit disconnect, or emergency ventilation condition.

### Claim 19 (depends on 17)

The non-invasive ventilator system of claim 17, wherein when the pressure at the proximal patient end of the tubing cannot be measured, an alternate proximal pressure estimate is substituted for the measurement based on an inlet circuit flow, a machine pressure measurement, and a calibrated model of tubing flow resistance.