Pulse Oximeter Plethysmography for Respiratory Effort and Apnea Discrimination
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Solution Overview
Problem
Existing devices struggle to accurately discriminate between obstructive sleep apnea (OSA) and central sleep apnea (CSA), and they lack the ability to monitor patient respiratory effort and cardiovascular parameters effectively, leading to sub-optimal treatment outcomes.
Innovation Solution
The use of a pulse oximeter to generate a patient effort signal, which is then used to derive an estimated breath phase independent of measured flow, allowing for improved discrimination between OSA and CSA, and enabling the monitoring of respiratory effort and cardiovascular parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the Forced Oscillation Technique is used to discriminate between OSA and CSA by injecting pressure oscillation and measuring flow, then open/closed airway discrimination is achieved, but the method cannot determine concurrent OSA and CSA events
Solution Approach 1:
The patent combines multiple monitoring approaches ( Forced Oscillation Technique for airway status, cardiogenic flow detection for central apnea, and pulse oximeter plethysmography for respiratory effort) into a unified system. This merging allows simultaneous detection of both obstructive and central sleep apnea events, resolving the limitation of using any single method alone.
Solution Approach 2:
The monitoring system is designed to perform multiple functions: discriminating open/closed airway status, detecting central apnea events, monitoring respiratory effort, and identifying concurrent apnea types. This multi-functional approach enables the system to handle diverse apnea scenarios that single-method systems cannot address.
2Measurement precision
If cardiogenic flow detection is used to discriminate between OSA and CSA, then central apnea detection is improved, but the method is unable to determine if CSA and OSA have occurred concurrently
Solution Approach 1:
The system merges cardiogenic flow detection with Forced Oscillation Technique and pulse oximeter plethysmography. This combination allows the system to simultaneously detect central apnea events (via cardiogenic flow) and obstructive events (via FOT), enabling identification of concurrent apnea types that neither method could detect alone.
3Measurement precision
If traditional effort monitoring methods (oesophageal catheter, respiratory bands, EMG sensors) are used to monitor patient respiratory effort, then measurement accuracy is achieved, but the devices are uncomfortable, awkward, or unsuitable for home use
Solution Approach 1:
The patent replaces complex mechanical effort monitoring systems (oesophageal catheters, respiratory bands, EMG sensors) with pulse oximeter plethysmography. This substitution maintains measurement accuracy for respiratory effort while eliminating the discomfort and complexity associated with traditional methods, making the system suitable for home use.
Solution Approach 2:
The pulse oximeter, already in use for oxygen saturation monitoring, is utilized to additionally provide respiratory effort information through plethysmography. This self-service approach eliminates the need for separate effort monitoring devices, reducing patient burden while maintaining measurement capabilities.
4Device complexity
If basic nasal CPAP ventilators are used without monitoring, then device simplicity is maintained, but patients lack the benefit of control loop monitoring for optimized treatment
Solution Approach 1:
The patent integrates multiple monitoring functions (airway status detection via FOT, central apnea detection via cardiogenic flow, respiratory effort monitoring via pulse oximeter plethysmography) into the CPAP system. This multi-functional monitoring capability enables optimized treatment through control loops while maintaining reasonable system complexity.
Solution Approach 2:
The system implements feedback control by using monitored parameters (airway status, respiratory effort, apnea events) to automatically adjust CPAP pressure settings. This feedback mechanism optimizes treatment reliability by continuously adapting to patient needs, addressing the limitation of non-monitoring basic CPAP devices.
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
This approach enhances the accuracy of apnea discrimination, reduces side effects, and allows for more effective auto-titration of CPAP pressure, thereby optimizing patient therapy and management.
Implementation Method 1
a pulse oximeter configured to generate, during a treatment period, a patient effort signal for input to control operation of the flow generator
Data Source
AI summary
In certain example embodiments, an air delivery system includes a controllable flow generator operable to generate a supply of pressurized breathable gas to be provided to a patient for treatment and a pulse oximeter. In certain example embodiments, the pulse oximeter is configured to determine, for example, a measure of patient effort during a treatment period and provide a patient effort signal for input to control operation of the flow generator. Oximeter plethysmogram data may be used, for example, to determine estimated breath phase; sleep structure information; autonomic improvement in response to therapy; information relating to relative breathing effort, breathing frequency, and/or breathing phase; vasoconstrictive response, etc. Such data may be useful in diagnostic systems.