Virtual Pressure Triggering for Active PEEP Ventilators

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Solution Overview

Problem

Mechanical ventilation systems with active extrinsic positive end-expiratory pressure (PEEP) maintenance face challenges in pressure-based triggering due to offset inhalation effort by increased blower flow, leading to ineffective triggering and potential spurious triggering from flow noise, which can desynchronize with patient's spontaneous inspiration.

Innovation Solution

A respiratory monitoring system that calculates a 'proxy' pressure by integrating gas flow into the lungs, estimating the pressure drop as if the exhalation valve were closed, and triggers inhalation gas delivery when this proxy pressure decreases below a threshold, mimicking passive PEEP control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If pressure triggering is used with active extrinsic PEEP maintenance, then the ventilator can maintain positive end-expiratory pressure, but the blower flow offsets the patient's inhalation effort, leading to ineffective triggering

Engineering Contradiction:

Improvetriggering effectivenessVSAvoidtrigger responsiveness

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent introduces a virtual pressure signal as an intermediary that mediates between the actual pressure measurements and the triggering decision. Instead of directly using the pressure sensor signal which is offset by blower flow, the system computes a virtual pressure that represents what the pressure would be without active PEEP maintenance, thereby restoring effective triggering while maintaining PEEP support

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system transforms the triggering parameter from direct pressure measurement to a computed virtual pressure parameter. By changing the parameter used for triggering from raw pressure to integrated flow-derived virtual pressure, the system eliminates the offset effect of blower flow while maintaining the ability to detect patient inhalation effort

Inventive Principle:

Principle #35Parameter changes

2Productivity

If pressure triggering threshold is set to detect patient effort, then inhalation can be triggered, but spurious triggering occurs from flow noise in the tubing circuit

Engineering Contradiction:

Improvebreath initiation detectionVSAvoidfalse trigger rate

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system performs preliminary integration of flow signals to compute virtual pressure before using it for triggering decisions. This preliminary processing of the flow data smooths out noise and transient fluctuations, allowing the system to distinguish between genuine patient effort and spurious flow noise, thereby reducing false triggers while maintaining sensitivity to real breaths

Inventive Principle:

Principle #10Preliminary action

3Ease of operation

If the ventilator suspends gas delivery during exhalation to enable pressure triggering, then triggering can occur based on pressure drop, but gas must flow between tubing and lungs which depletes the tubing pressure

Engineering Contradiction:

Improvetriggering mechanismVSAvoidgas volume in tubing

Core Design Contradiction:

Ease of operationVSQuantity of substance

Solution Approach 1:

The patent replaces the mechanical pressure-based triggering system with a computational flow-integration system. Instead of relying on physical pressure drops in the tubing that deplete gas volume, the system uses electronic integration of flow signals to compute virtual pressure, thereby eliminating the need for gas depletion while maintaining triggering functionality

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 sensitivity to leaks, and maintains synchronicity with patient's breathing efforts, even with active PEEP control, by using a proxy pressure calculation to determine the appropriate threshold for inhalation gas delivery.

Implementation Method 1

a pressure sensor connected to measure gas pressure at the patient port

Methodology Applied

Scientific EffectPressure sensing:

Implementation Method 2

a gas flow meter connected to measure gas flow into lungs of the patient

Methodology Applied

Scientific EffectFlow measurement:

Implementation Method 3

compute a proxy pressure comprising an integral of gas flow into the lungs measured by the gas flow meter

Methodology Applied

Scientific EffectIntegration of flow to compute pressure:

Data Source

PatentUS11904093B2Ventilator gas delivery initiation via a virtual pressure triggering mechanism

Publication Date: 2024.02.20 KONINKLIJKE PHILIPS NV

AI summary

A respiratory monitoring system includes (10) a mechanical ventilator (12) configurable to perform a ventilation mode in 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.