Ventilator Triggering via Virtual Pressure Under Active PEEP
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Solution Overview
Problem
In mechanical ventilation systems that maintain positive end-expiratory pressure (PEEP) actively, pressure-based triggering is ineffective due to offsetting inhalation effort by increased blower flow, leading to potential spurious triggering from flow noise, which can desynchronize with the patient's spontaneous inspiration.
Innovation Solution
The implementation of a 'proxy' pressure calculation, where the inhalation gas delivery phase is triggered when a computed proxy pressure decreases below a threshold, mimicking the pressure drop if the exhalation valve were closed, using the equation Pprox(t) = PEEP − ∫[To tf] Qlung(t) / Ctube dt, where PEEP is the extrinsic PEEP level, Qlung(t) is the gas flow into the lungs, and Ctube is the tubing circuit compliance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure-based triggering is used in mechanical ventilation with active PEEP maintenance, then the ventilator can detect patient's breathing effort, but spurious triggering occurs due to flow noise offsetting the pressure drop
Solution Approach 1:
The patent introduces a virtual pressure calculation as an intermediary mechanism that combines actual pressure measurements with flow integration to create a corrected triggering signal. This virtual pressure acts as a mediator that filters out the spurious effects of flow noise while preserving the patient's genuine breathing effort detection.
Solution Approach 2:
The patent replaces the direct mechanical pressure-based triggering system with a computational approach that uses integrated flow measurements to derive virtual pressure. This substitution transforms the triggering mechanism from a purely pressure-sensitive system to one that uses computational processing of flow and pressure data.
2Reliability
If flow-based triggering is used to avoid spurious pressure triggering, then auto-triggering from leaks is reduced, but desynchronization with patient's spontaneous inspiration occurs
Solution Approach 1:
The patent merges flow-based triggering and pressure-based triggering into a unified virtual pressure calculation. By integrating flow measurements over time and combining them with pressure data, the system achieves the leak resistance of flow triggering while maintaining the breathing effort detection accuracy of pressure triggering.
3Stress or pressure
If active PEEP maintenance is implemented, then positive end-expiratory pressure is maintained, but pressure triggering becomes ineffective due to offsetting blower flow
Solution Approach 1:
The patent changes the parameter used for triggering from direct pressure to virtual pressure derived from integrated flow. This parameter transformation allows the system to maintain accurate triggering detection while active PEEP and blower flow are present, as the virtual pressure calculation accounts for the cumulative effect of flow into the circuit.
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 improves monitoring of pressure levels during ventilation, reduces auto-triggering due to leaks, and maintains synchronicity with the patient's breathing effort, providing a pressure threshold related to passive PEEP settings, thus avoiding spurious flow-based triggering.
Implementation Method 1
a gas flow meter connected to measure gas flow into lungs of the patient
Implementation Method 2
a pressure sensor connected to measure gas pressure at the patient port
Implementation Method 3
compute a proxy pressure based on an integral of gas flow into the lungs measured by the gas flow meter
Data Source
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AI summary
A respiratory monitoring system includes (10) a mechanical ventilator (12) configurable to perform a ventilation mode that includes an inhalation gas delivery phase and provides extrinsic positive end-expiratory pressure (PEEP) at a PEEP level during an exhalation phase. A breathing tubing circuit (26) includes: a patient port (28), a gas inlet line (16) connected to supply gas from the mechanical ventilator to the patient port, a gas flow meter (30) connected to measure gas flow into lungs of the patient, and a pressure sensor (32) connected to measure gas pressure at the patient port. At least one processor (38) is programmed to: compute a proxy pressure comprising an integral of gas flow into the lungs measured by the gas flow meter; and trigger the inhalation gas delivery phase of the ventilation mode when the proxy pressure decreases below a trigger pressure threshold.