CPAP Air Delivery Conduit Sizing for Stable Pressure Control

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Solution Overview

Problem

Existing CPAP systems face issues with large and bulky air delivery conduits that cause discomfort, interfere with the patient's environment, and are restrictive in communicating airflow and electrical signals, leading to high impedance and pressure swings.

Innovation Solution

A CPAP system with a smaller diameter air delivery conduit (less than 22 mm outer diameter and 19 mm internal diameter) that includes a heated option with reduced surface area, lower heat loss, and a recognition system to adjust operating parameters based on conduit type, combined with a low inertia blower and advanced pressure control algorithms to compensate for impedance and pressure disturbances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If medical grade tubing with 22 mm outer diameter is used, then the tubing can communicate airflow effectively, but the tubing becomes bulky, looks out of place in bedroom environment, and causes high impedance

Engineering Contradiction:
Improveairflow communicationVSAvoidvisual discomfort and environmental interference
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the dimensional parameters of the tubing from standard 22 mm outer diameter to smaller dimensions (15-18 mm outer diameter), transforming the tubing from bulky medical grade to compact home-use size while maintaining airflow communication capability through optimized internal geometry

Inventive Principle:
Principle #35Parameter changes

2Object-affected harmful factors

If smaller diameter tubing is used, then the tubing becomes more compact and comfortable, but the impedance increases and pressure swings occur

Engineering Contradiction:
Improvevisual discomfort and bulkVSAvoidpressure stability
Core Design Contradiction:
Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent optimizes the internal diameter and wall thickness parameters of the tubing to achieve a balance between compact external dimensions and adequate internal airflow capacity, reducing impedance while maintaining small size

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The system incorporates pressure sensing and control mechanisms that provide feedback to compensate for impedance variations and pressure swings caused by the smaller tubing dimensions, maintaining stable pressure delivery

Inventive Principle:
Principle #23Feedback

3Ease of manufacture

If standard 22 mm tubing is used, then the tubing is easily available and standardized, but the tubing causes high impedance and requires external insulation accessories

Engineering Contradiction:
ImprovestandardizationVSAvoidadditional accessories required
Core Design Contradiction:
Ease of manufactureVSDevice complexity

Solution Approach 1:

The patent establishes a new standard tubing dimension (15-18 mm outer diameter) that integrates electrical signal communication capability directly into the tubing structure, eliminating the need for separate external insulation accessories and reducing system complexity

Inventive Principle:
Principle #35Parameter changes

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 system provides a more comfortable, compact, and efficient CPAP therapy with reduced power consumption, less rainout, and improved patient compliance by minimizing impedance and pressure swings.

Implementation Method 1

The air delivery conduit having a reduced overall surface area compared to a standard 22 mm outer diameter air delivery conduit

Methodology Applied
Scientific EffectThermal energy transfer: Conduction (thermal)

Implementation Method 2

provides less heat loss in the air delivery conduit

Methodology Applied
Scientific EffectHeat loss reduction: Thermal Insulation

Implementation Method 3

a flow generator including a blower that supplies breathable gas at pressure

Methodology Applied
Scientific EffectPressure generation: Pressure Increase

Implementation Method 4

The air delivery conduit having a reduced overall surface area compared to a standard 22 mm outer diameter air delivery conduit

Methodology Applied
Scientific EffectHeat transfer: Conduction (thermal)

Data Source

PatentEP3821928B1CPAP systems
Publication Date: 2026.04.01 RESMED PTY LTD
  • EP3821928B1 patent drawingFigure 1~3
  • EP3821928B1 patent drawingFigure 4
  • EP3821928B1 patent drawingFigure 5

AI summary

The present disclosure relates to a continuous positive airway pressure, CPAP, system comprising: a flow generator including a blower that supplies breathable gas at pressure; a patient interface; and an air delivery conduit interconnecting the flow generator and the patient interface, the air delivery conduit including a conduit portion having an internal diameter of less than 19 mm.