# US 10,869,977 B2 · System and method for accurate estimation of intentional and unintentional leaks in flow generation systems

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- Number: US 10,869,977 B2
- Document ID: US10869977B2
- Status: Granted
- Kind: B2
- Application number: 15/498,601
- Filed: 2017-04-27
- Published: 2017-11-02
- Granted: 2020-12-22
- Earliest claimed: 2016-04-28
- Assignees: Invent Medical Corporation
- Applicants: Invent Medical Corporation
- Inventors: Samuel M. Chang; Nhien M. Nguyen
- Web page: https://patentgrep.com/patent/US10869977B2

## CPC

- A61M 16/0069: {the speed thereof being controlled by respiratory parameters, e.g. by inhalation}
- A61M 16/0051: {with alarm devices}
- 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 16/1005: {with O2 features or with parameter measurement}
- A61M 16/1045: {Devices for humidifying or heating the inspired gas by using recovered moisture or heat from the expired gas}
- A61M 16/1055: {bacterial}
- A61M 16/125: {Diluting primary gas with ambient air}
- A61M 16/16: Devices to humidify the respiration air {(A61M16/1045 takes precedence)}
- A61M 16/208: {Non-controlled one-way valves, e.g. exhalation, check, pop-off non-rebreathing valves}
- G01M 3/26: by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors
- G01M 3/28: for pipes, cables or tubes; for pipe joints or seals; for valves {; for welds}
- A61M 16/0672: {Nasal cannula assemblies for oxygen therapy}
- A61M 2016/0027: {pressure meter}
- A61M 2016/0033: {electrical}
- A61M 2016/0039: {in the inspiratory circuit}
- A61M 2202/0208: Oxygen
- A61M 2205/15: Detection of leaks
- A61M 2205/50: with microprocessors or computers
- 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)}
- G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR

## Abstract

In one embodiment, a method for accurate leak estimation in a flow generation system includes measuring a total flow through the flow generation system, measuring a pressure in the primary flow circuit of the flow generation system, determining when the measured pressure is within a predetermined threshold of EPAP, and calculating an intentional leak flowrate and an unintentional leak flowrate based on the relationship QFS(t)=QIL(t)+QUL(t) when the measured pressure is within the predetermined threshold. In another embodiment, a flow generation system includes in one embodiment an airflow generator connected in-line to a flow sensor, a pressure sensor and a patient interface connection by a first gas flow circuit, and a controller electrically coupled to the airflow generator, the flow sensor and the pressure sensor. The controller sends a control signal to the airflow generator based on a first flow value measured from the flow sensor and an unintentional leak flow value that is derived from a proportional relationship with an intentional leak flow value.

## Claims

### Claim 1

A method for accurate leak estimation in a flow generation system comprising:
measuring, with a flow sensor, a total flow through the flow generation system;
measuring, with a pressure sensor, a pressure in a primary flow circuit of the flow generation system (PPS(t));
determining when the measured PPS(t) indicates no breathing by determining when PPS(t) is within a predetermined threshold of EPAP indicating that PPS(t)≅EPAP, when PPS(t) is within 1 cmH2Q from EPAP; and
calculating an intentional leak flowrate and an unintentional leak flowrate based on the relationship QFS(t)=QIL(t)+QUL(t) when the measured pressure is within the predetermined threshold.

### Claim 2 (depends on 1)

The method of claim 1, wherein the total flow includes a first flow source comprising ambient air and a second flow source comprising pressurized oxygen.

### Claim 3 (depends on 2)

The method of claim 2, the total flow includes a third flow source.

### Claim 4 (depends on 1)

The method of claim 1, wherein the primary flow circuit comprises the flow sensor for measuring the total flow, an airflow generator and a patient interface connection.

### Claim 5 (depends on 1)

The method of claim 1, wherein PPS(t)≅EPAP when PPS(t) is within 0.5 cmH2O from EPAP.

### Claim 6 (depends on 1)

The method of claim 1, wherein PPS(t)≅EPAP when PPS(t) is within 0.2 cmH2O from EPAP.

### Claim 7 (depends on 1)

The method of claim 1, wherein PPS(t)≅EPAP when PPS(t) is within 0.1 cmH2O from EPAP.

### Claim 8 (depends on 1)

The method of claim 1 further comprising:
determining the intentional leak flow rate at least partially based on a selected patient interface orifice size.

### Claim 9 (depends on 1)

The method of claim 1 further comprising:
determining a flowrate of the lungs QIL(t) by satisfying the equations:
QFS(t)=QIL(p,t)+QUL(p,t)+QL(t)
when PPS(t)≅EPAP,
QFS(t)=QIL(t)+QUL(t), and
QUL(p,t)=∝·QIL(p,t).

### Claim 10 (depends on 1)

The method of claim 1 further comprising:
determining a flowrate of the lungs QIL(t) by satisfying the equations:
QFS(t)=QIL(p,t)+QUL(p,t)+QL(t)
when PPS(t)≅EPAP, and
QFS(t)=QIL(t)+QUL(t).

### Claim 11 (depends on 1)

The method of claim 1 further comprising modeling an orifice equation for a total leak using an empirical equation.