Capnogram Display With Airflow Direction Sensing
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Solution Overview
Problem
Existing capnography devices cannot distinguish between the direction of airflow during breathing cycles, leading to uncertainty about whether a patient is inhaling CO2-rich air they have exhaled or experiencing pauses in breathing, which can be life-threatening.
Innovation Solution
A breath monitoring apparatus with an airflow direction sensor and CO2 monitor that produces a capnogram displaying CO2 levels versus time, using different graphical qualities to indicate airflow direction, allowing clinicians to differentiate between inhaled, exhaled, and stationary air CO2 levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a CO2 monitor is used to measure CO2 levels in breath, then CO2 level data is obtained, but the direction of airflow (inhalation vs exhalation) cannot be determined
Solution Approach 1:
The patent segments the CO2 waveform data by creating separate graphical representations for inhalation and exhalation phases. The processor divides the continuous CO2 signal into distinct segments based on airflow direction detected by the flow sensor, allowing independent visualization and analysis of CO2 levels during inspiration and expiration.
Solution Approach 2:
The patent adds a temporal dimension to the CO2 measurement by introducing time delays between displaying CO2 level data and airflow direction data. This allows the system to align and correlate CO2 measurements with the corresponding breathing phase by offsetting one signal relative to the other in the time domain.
2Speed
If CO2 levels are displayed in real-time, then immediate monitoring is achieved, but the data may be misaligned with corresponding airflow phases
Solution Approach 1:
The system performs preliminary alignment by calculating and applying appropriate time delays to synchronize CO2 measurements with airflow phase detection. Before displaying the data, the processor pre-adjusts the timing of CO2 readings to account for the time required for gas transport through the sampling system, ensuring accurate correlation between CO2 levels and breathing phases.
Solution Approach 2:
The system uses feedback from the airflow direction sensor to continuously adjust and refine the alignment between CO2 measurements and breathing phases. The flow sensor provides real-time feedback about inhalation and exhalation states, which the processor uses to dynamically adjust the time delay and ensure accurate data correspondence throughout the monitoring process.
3Loss of information
If different graphical qualities are used to distinguish airflow directions, then breathing phase information becomes visible, but the display complexity increases
Solution Approach 1:
The patent employs color changes to differentiate between inhalation and exhalation phases in the capnogram display. Different colors are assigned to represent different airflow directions and CO2 concentration ranges, providing intuitive visual cues that enhance the information content without requiring complex additional hardware or processing.
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
Enables immediate and understandable visualization of CO2 rebreathing and breathing status, facilitating rapid response to potentially life-threatening situations by clearly distinguishing between CO2 levels associated with inhalation, exhalation, and pauses in breathing.
Implementation Method 1
a differential pressure sensor attached to two apertures provided in the airflow means tube arranged linearly with respect to one another such that one aperture is downstream of the other
Implementation Method 2
a CO2 monitor for repeatedly determining the presence, and level, of CO2 in the air within the airflow means
Data Source
Figure 1~2
AI summary
It is known to produce capnograms showing levels of CO2 in a patient's breath when they breathe-out. This apparatus is able to produce a capnogram (100) for a patient, comprising airflow means (30) arrangeable such that air flowing into and out of a patient during a breathing cycle of the patient are conducted through the airflow means; a CO2 monitor (50) for repeatedly determining the presence, and level, of CO2 in the air within the airflow means; an airflow direction sensor (40) for distinguishing between periods when air is flowing into the patient, when air is flowing out of the patient, and when air in the airflow means is stationary; a processor (70) for producing a graph on a display (90) of time versus an indication of CO2 levels, wherein the display includes different graphical qualities (142, 144, 146) to distinguish between the level of CO2 in the air flowing out of the patient, the level of CO2 in the stationary air between breaths, and the level of CO2 in the air flowing into the patient.