Variable Cycling Threshold Ventilator Synchronization
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Solution Overview
Problem
Current ventilator technologies face challenges in accurately synchronizing pressure responses with a patient's respiratory cycle, particularly in abnormal respiratory mechanics, leading to improper detection of expiration and reduced support during inspiration in conditions like COPD, resulting in discomfort and potential dynamic hyperinflation.
Innovation Solution
A variable cycling threshold that changes as a function of time within the inspiratory cycle, becoming more sensitive towards the end, and incorporating a refractory period to prevent premature transitions, ensuring accurate synchronization and optimal gas exchange.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed threshold is used for cycling detection, then the device structure is simple, but synchronization accuracy deteriorates in abnormal respiratory mechanics
Solution Approach 1:
The patent applies the dynamics principle by making the cycling threshold variable rather than fixed. The threshold dynamically adjusts based on the inspiratory time and respiratory phase, allowing the system to adapt to abnormal respiratory mechanics in COPD patients. This dynamic adjustment improves synchronization accuracy without requiring complex additional hardware, as the complexity is managed through software control algorithms.
Solution Approach 2:
The patent implements parameter changes by modifying the cycling threshold parameter as a function of inspiratory time. The threshold evolves from a less sensitive initial value to a more sensitive final value during the inspiratory phase. This parameter transformation allows the system to accurately detect expiration events across varying respiratory patterns while maintaining a relatively simple device structure.
2Measurement precision
If cycling threshold is highly sensitive, then expiration detection accuracy is improved, but premature cycling into expiration may occur
Solution Approach 1:
The patent applies preliminary action by establishing a refractory period that prevents cycling detection during the early inspiratory phase. This preliminary restriction on cycling capability ensures that even when the threshold becomes highly sensitive later in the inspiratory phase, premature cycling cannot occur. The refractory period acts as a preventive measure that maintains cycling stability while allowing high sensitivity detection later in the breath cycle.
Solution Approach 2:
The system dynamically adjusts the cycling threshold sensitivity throughout the inspiratory phase. The threshold starts as less sensitive during early inspiration and progressively becomes more sensitive toward the end of inspiration. This dynamic sensitivity adjustment allows the system to avoid premature cycling while maintaining high detection accuracy for genuine expiration events near the end of the intended inspiratory time.
3Ease of operation
If fixed inspiratory time is used, then device operation is simple, but dynamic hyperinflation occurs in COPD patients
Solution Approach 1:
The patent implements dynamics by making the effective inspiratory time variable rather than fixed. The system allows the inspiratory phase to extend beyond a predetermined time limit when respiratory mechanics indicate the need for longer inspiration. This dynamic time adjustment prevents dynamic hyperinflation in COPD patients by adapting the inspiratory duration to actual patient needs, while the overall control structure remains relatively simple through automated detection algorithms.
Solution Approach 2:
The system uses feedback from continuous monitoring of respiratory flow and pressure to determine when to extend the inspiratory phase beyond the predetermined time limit. The feedback mechanism detects ongoing inspiration patterns and adjusts the cycling point accordingly, preventing premature termination that would cause dynamichyperinflation. This feedback-based adjustment maintains ease of operation as the system autonomously adapts without requiring complex manual intervention.
Data Source
AI summary
A ventilator that delivers air at different pressures to a patient during inspiratory and expiratory cycles of breathing and that cycles from inspiratory to expiratory operation when the patient's respiratory flow passes a threshold level. The threshold generally increases from the beginning of inspiration to the end of inspiration. The increase can be linear over all or only a portion of the inspiratory cycle, and the threshold can be adjusted so that cycling is prevented during the initial portion of an inspiratory cycle. The minimum and maximum levels may both be functions of peak flow and the threshold may increase as a function of elapsed inspiratory time. The rate at which the threshold increases from a minimum level to a maximum level may be adjustable for individual patient needs and may be determined from previous breaths.