Ventilator Lung Compliance Estimation via Extended Inspiratory Hold
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Solution Overview
Problem
Conventional methods for measuring respiratory parameters in mechanically ventilated patients, such as lung compliance and resistance, often result in inaccurate readings due to lung pressure overshoot during the pause maneuver and assume a passive patient, which does not reflect therapeutic mechanical ventilation conditions.
Innovation Solution
A respiratory device with an airway pressure sensor and airway flow sensor, controlled by an electronic processor, provides a pressure-controlled breath with an extended inspiratory interval to maintain airway pressure at a preset level, allowing for accurate measurement of lung compliance and elastance without overshoot, even in actively breathing patients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pause maneuver is used to measure respiratory parameters, then lung pressure can equilibrate for parameter assessment, but lung pressure overshoot occurs causing measurement inaccuracy
Solution Approach 1:
The patent applies preliminary action by extending the inspiratory hold time before measurement to allow respiratory muscle pressure to fully vanish. This preliminary extension ensures that when the actual measurement begins, all active muscle pressure has already dissipated, eliminating the source of pressure overshoot and enabling accurate compliance and resistance measurements without the harmful overshoot effect.
2Measurement precision
If conventional measurement methods are used, then respiratory parameters can be estimated, but the methods assume a passive patient which does not reflect therapeutic mechanical ventilation conditions
Solution Approach 1:
The patent applies dynamics by implementing a time-varying measurement approach that specifically addresses active patient conditions. The method dynamically extends the inspiratory hold period and uses real-time detection of when muscle pressure vanishes (through flow zero-crossing detection) to determine the optimal measurement window. This dynamic adaptation allows accurate parameter estimation in active patients while maintaining therapeutic ventilation conditions, making the system versatile for both passive and active patient states.
3Measurement precision
If the inspiratory breath interval is extended to allow muscle pressure to vanish, then measurement accuracy improves, but the measurement time increases
Solution Approach 1:
The patent applies feedback by using airway flow detection to monitor when the flow rate reaches zero, which indicates that respiratory muscle pressure has vanished. This feedback mechanism allows the system to dynamically determine the optimal end point for the extended inspiratory hold, ensuring measurements are taken at the precise moment when muscle pressure is eliminated. This feedback-based approach minimizes the extended time required while guaranteeing measurement accuracy, as the system stops extending the hold interval as soon as the zero-flow condition is detected.
Data Source
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AI summary
A mechanical ventilator (10) is controlled by an electronic processor (14) to provide respiratory support to a patient (12) using a pressure controlled ventilation mode while being monitored by an airway pressure sensor (30) and an airway flow sensor (32). The electronic processor also controls the ventilator to perform a respiratory system measurement process (44) including: controlling the ventilator to provide a pressure controlled breath at a preset pressure (Ppreset) over an extended inspiratory breath interval that is extended by an extension time interval (TIE) beyond end of physiological inspiration; controlling an exhalation valve (40) at least during the extension time interval to maintain airway pressure at the preset pressure (Ppreset). Lung compliance or elastance is determined from airway pressure measurements and airway flow measurements acquired during the extended inspiratory breath interval.