# US 8,739,789 B2 · Respiratory apparatus with improved flow-flattening detection

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- Number: US 8,739,789 B2
- Document ID: US8739789B2
- Status: Granted
- Kind: B2
- Application number: 11/611,315
- Filed: 2006-12-15
- Published: 2007-04-19
- Granted: 2014-06-03
- Earliest claimed: 2000-08-29
- Assignees: ResMed Limited
- Applicants: Nicola Frances Wickham
- Inventors: Peter John D. Wickham
- Web page: https://patentgrep.com/patent/US8739789B2

## CPC

- A61B 5/7278: {Artificial waveform generation or derivation, e.g. synthesizing signals from measured signals}
- A61B 5/085: Measuring impedance of respiratory organs or lung elasticity
- A61B 5/087: Measuring breath flow
- A61B 5/4818: {Sleep apnoea}
- A61B 5/7282: {Event detection, e.g. detecting unique waveforms indicative of a medical condition (cough events A61B5/0823; seizures A61B5/4094; sleep apnoea A61B5/4818)}
- A61M 16/0069: {the speed thereof being controlled by respiratory parameters, e.g. by inhalation}
- A61M 16/024: {including calculation means, e.g. using a processor}
- A61M 16/0066: {Blowers or centrifugal pumps}
- A61M 16/06: Respiratory or anaesthetic masks
- A61M 2016/0039: {in the inspiratory circuit}
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- 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

In a respiratory apparatus for treatment of sleep apnea and other disorders associated with an obstruction of a patient's airway and which uses an airflow signal, an obstruction index is generated which detects the flattening of the inspiratory portion of the airflow. The obstruction index is used to differentiate normal and obstructed breathing. The obstruction index is based upon different weighting factors applied to sections of the airflow signal thereby improving sensitivity to various types of respiration obstructions.

## Claims

### Claim 1

An apparatus for determining the presence of an obstruction in the airway of a patient comprising:
a sensor for sensing the flow of air during the inspiration portion of a patient's breath and for generating a sensor signal representing the air flow in a patient's airway;
a mechanism coupled to said sensor for processing successive samples of said sensor signal using successive varying weighting factors to derive successive weighted samples; and
a processor for comparing a function based on said weighted samples to an obstruction threshold to determine the presence of an airway obstruction,
wherein said function is a measure of the flatness of the inspiration portion of the patient's breath.

### Claim 2 (depends on 1)

The apparatus of claim 1 wherein each of said successive weighing factors is determined based upon the magnitude of each sample.

### Claim 3 (depends on 1)

The apparatus of claim 1 wherein each of said successive weighing factors is determined based upon the time position of each sample.

### Claim 4 (depends on 1)

The apparatus of claim 1 wherein each of said successive weighing factors is determined based upon a comparison to a threshold value.

### Claim 5

A method for determining the presence of an obstruction in the airway of a patient comprising the steps of:
generating for the inspiratory portion of the respiratory cycle a signal representing the air flow in a patient's airway;
processing successive samples of the generated signal using successive varying weighting factors to derive successive weighted samples; and
comparing the value of a function based on said weighted samples to an obstruction threshold to determine the presence of an airway obstruction,
wherein said function is a measure of the flatness of the inspiration portion of the patient's breath.

### Claim 6 (depends on 5)

The method of claim 5 wherein each of said successive weighing factors is determined based upon the magnitude of each sample.

### Claim 7 (depends on 5)

The method of claim 5 wherein each of said successive weighing factors is determined based upon the time position of each sample.

### Claim 8 (depends on 5)

The method of claim 5 wherein each of said successive weighing factors is determined based upon a comparison to a threshold value.