Mainstream Exhaled Oxygen Sensing With Compact Multi-Pass Optics
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Solution Overview
Problem
Existing oxygen sensors for breath monitoring are bulky, inaccurate, or have slow response times, failing to meet the demands of high temporal resolution and accuracy required for real-time metabolic function analysis in critical care settings.
Innovation Solution
A compact, lightweight sensor using laser spectroscopy with a miniaturized multi-pass cell and lock-in amplifier for high sensitivity and precision, capable of measuring oxygen concentration cycles in breath with a sampling rate of 100 Hz and precision of <0.5% O2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If long absorption pathlengths or optical enhancement techniques are used to compensate for small absorption cross-sections of O2, then detection sensitivity is improved, but sensor size and sampling volume increase making it bulky
Solution Approach 1:
The patent employs a multi-pass cell configuration that folds the optical path through the sample gas multiple times using mirrors, effectively increasing the absorption pathlength from a linear dimension to a multi-dimensional optical path. This allows achieving long effective pathlengths (several meters) within a compact physical volume, resolving the contradiction between detection sensitivity and sensor size.
2Measurement precision
If conventional oxygen monitoring techniques are used, then device simplicity is maintained, but temporal resolution and measurement accuracy are insufficient for critical care applications
Solution Approach 1:
The patent replaces conventional mechanical or electrochemical oxygen sensing mechanisms with laser-based spectroscopic detection. The system uses a tunable diode laser tuned to the oxygen A-band absorption feature, enabling high temporal resolution measurements at 100 Hz sampling rate while maintaining a relatively compact and integrated device architecture suitable for clinical use.
3Measurement precision
If high sampling rate of 100 Hz is implemented to capture breath cycle dynamics, then temporal resolution is improved, but response time and measurement speed demands increase
Solution Approach 1:
The patent implements continuous wave laser operation with real-time detection and signal processing to maintain uninterrupted oxygen concentration measurements at 100 Hz sampling rate. The system continuously tracks oxygen absorption features through the breath cycle, providing uninterrupted temporal resolution without requiring mechanical resetting or intermittent measurements, thus achieving both high sampling rate and fast response time.
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
The sensor achieves real-time, precise measurement of oxygen concentration with a response time of 10 ms, enabling continuous monitoring of metabolic function and aiding in clinical diagnostics such as neonatal complications and hypoxia detection.
Implementation Method 1
a laser configured to emit light at an A-band of oxygen... The light passes through the multi-pass cell and is attenuated by oxygen in the sample cell
Implementation Method 2
The light passes through the multi-pass cell and is attenuated by oxygen in the sample cell
Implementation Method 3
a photodetector configurated to convert the attenuated light into an electrical signal
Data Source
AI summary
According to various embodiments, a sensing device for measuring oxygen concentration cycles in breath is disclosed. The sensing device includes a laser configured to emit light at an A-band of oxygen, a lens configured to collimate the light, and a multi-pass cell configured to contain a replaceable sample cell. The light passes through the multi-pass cell and is attenuated by oxygen in the sample cell. The sensing device further includes a photodetector configurated to convert the attenuated light into an electrical signal, and a lock-in amplifier or an equivalent processing circuit configured to determine oxygen concentration from the electrical signal.