Respiratory Flow Frequency Analysis for Unsealed Breathing Rate Monitoring

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Solution Overview

Problem

Determining respiratory rate in unsealed respiratory systems, such as nasal high flow therapy, is challenging due to turbulent flow and noise in the signal, leading to inaccurate breath detection and compromised accuracy in respiratory rate measurement.

Innovation Solution

Performing frequency analysis of gases flow parameters, including flow rate, pressure, and motor speed, to extract magnitude and frequency information, providing more reliable respiratory rate data and improving accuracy by using processors to determine respiratory rate and patient connection status.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If frequency analysis is performed on respiratory gas flow signals, then respiratory rate monitoring accuracy is improved, but device complexity increases

Engineering Contradiction:
Improverespiratory rate monitoring accuracyVSAvoiddevice complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The respiratory device performs multiple functions using a single sensor system: it monitors respiratory rate, detects patient interface removal, identifies talking/eating events, and provides therapy compliance tracking. This multi-functionality approach improves measurement precision without proportionally increasing device complexity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system uses the patient's own respiratory gas flow characteristics to automatically determine respiratory rate and detect various patient states. The frequency analysis is performed on signals naturally generated by the patient's breathing, eliminating the need for additional active sensors or complex external monitoring equipment.

Inventive Principle:
Principle #25Self-service

2Ease of operation

If non-sealed patient interface is used, then ease of operation is improved, but measurement precision deteriorates

Engineering Contradiction:
Improveease of operationVSAvoidmeasurement precision
Core Design Contradiction:
Ease of operationVSMeasurement precision

Solution Approach 1:

The system continuously monitors the respiratory gas flow signal and provides feedback about patient status (respiratory rate, interface removal, talking, eating). This feedback mechanism allows the system to adapt to varying conditions and maintain measurement precision even with non-sealed interfaces that may have variable contact.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The system analyzes changes in the frequency parameters of the respiratory gas flow signal to detect different patient states. By monitoring parameter variations rather than relying on fixed contact conditions, the system maintains measurement precision with non-sealed interfaces while preserving ease of operation.

Inventive Principle:
Principle #35Parameter changes

3Loss of information

If frequency analysis is performed on respiratory gas flow signals, then therapy compliance monitoring is improved, but use of energy increases

Engineering Contradiction:
Improvetherapy compliance monitoringVSAvoiduse of energy
Core Design Contradiction:
Loss of informationVSUse of energy by moving object

Solution Approach 1:

The system performs continuous frequency analysis of the respiratory gas flow signal throughout the therapy period to continuously monitor respiratory rate and detect patient status changes. This continuous monitoring provides comprehensive therapy compliance data without requiring intermittent sampling, improving information quality while using energy efficiently through continuous low-power signal processing.

Inventive Principle:
Principle #20Continuity of useful action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The frequency analysis method enhances respiratory rate measurement accuracy and detects patient disconnection, improving therapy compliance monitoring and long-term respiratory function tracking.

Implementation Method 1

performing one or more frequency analyses of a signal from the gases flow

Methodology Applied
Scientific EffectFrequency analysis:

Data Source

PatentEP4438094B1Respiratory rate monitoring for respiratory flow therapy systems
Publication Date: 2026.05.13 FISHER & PAYKEL HEALTHCARE LTD
  • EP4438094B1 patent drawingFigure 1
  • EP4438094B1 patent drawingFigure 2
  • EP4438094B1 patent drawingFigure 3

AI summary

Systems and methods can determine respiratory rates of a patient using a respiratory device by performing one or more frequency analyses of a signal from the gases flow. The signal from the gases flow can be one that varies with the patient's breathing. The system can include a non-sealed patient interface, such as a nasal cannula in a nasal high flow therapy, or any other patient interfaces. The respiratory system can also detect whether the patient has taken off the patient interface and/or whether the patient connected to the patient interface is talking or eating. Data of the patient's use of the respiratory system and the patient's respiratory rates can provide therapy compliance and long-term trend of use information and/or progress in the patient's respiratory functions and/or other physiological functions.