Nasal Sensor Directional Flow Detection
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Solution Overview
Problem
Current nasal sensors that measure airflow using thermistors are insensitive to the direction of flow, leading to false detections and inability to accurately observe inhalation onsets, especially in cases of shallow breathing or small temperature differences.
Innovation Solution
A nasal sensor system that includes a light emitter and detector, along with detection modification elements such as thermosensitive elements or opto-mechanical units, to differentiate between inflowing and outflowing air based on light transmission changes, enabling direction-sensitive respiratory flow measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thermistor-based nasal sensor is used to measure airflow, then respiration rate can be detected through temperature changes, but the sensor cannot distinguish between inhalation and exhalation directions leading to false detections
Solution Approach 1:
The sensor is divided into two separate detection elements: a thermistor for temperature-based respiration rate detection and a flow direction sensor (such as a hot wire anemometer or pressure differential sensor) for determining inhalation/exhalation direction. This segmentation allows each element to specialize in one function, improving overall measurement precision while eliminating the reliability issue of direction sensitivity
Solution Approach 2:
A flow direction detection mechanism acts as an intermediary between the thermistor and the respiration rate calculation system. This intermediary provides directional information that allows the system to filter out false detections caused by ambient air flow and to accurately distinguish between inhalation and exhalation phases
2Measurement precision
If only temperature changes are detected by the thermistor, then respiration rate can be measured, but the sensor is insensitive to shallow breathing or small temperature differences
Solution Approach 1:
The thermistor-based temperature detection is merged with an additional detection mechanism such as a hot wire anemometer, pressure differential sensor, or optical flow sensor. This combination allows the system to detect both temperature changes and flow characteristics, providing redundant information that improves detection sensitivity for shallow breathing where temperature changes are minimal
Solution Approach 2:
The system monitors multiple parameters simultaneously: temperature change (from thermistor), flow rate (from anemometer or pressure sensor), and potentially humidity change. By analyzing changes in multiple parameters rather than relying solely on temperature, the system can detect shallow breathing events that produce only subtle thermal signals
3Measurement precision
If ambient air flows into the nose due to a fan or other external source, then false detections occur leading to erroneous respiration rates, but the sensor cannot differentiate between external and internal air flow
Solution Approach 1:
A flow direction sensor with a defined sensing direction is positioned to detect only air flow from the subject's nose. This directional sensitivity acts as a simple filter that rejects external air flow (such as from fans) that does not originate from the nasal cavity, thereby eliminating false detections without requiring complex signal 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
This solution allows for robust detection of exhalations, determination of respiration rate, and identification of inhalation cycles, improving the accuracy of physiological information monitoring and enabling efficient operation of devices like oxygen concentrators.
Implementation Method 1
a light emitter secured to the first support and configured to emit light in at least one wavelength range towards the second nostril; a light detector secured to the first or second support and configured to detect light in the at least one wavelength range
Implementation Method 2
one or more detection modification elements secured to the second support and configured to change the amount of light detected by the light detector based on the direction of flow of air within the second nostril
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The present invention relates to a nasal sensor (10, 110, 210), system and method for determining physiological information of a subject. The nasal sensor comprises a nasal mount (11, 12, 13), a light emitter (20, 21) secured to the first support and configured to emit light in at least one wavelength range towards the second nostril, a light detector (30, 31) secured to the first or second support and configured to detect light in the at least one wavelength range, and one or more detection modification elements (40, 41, 42, 43, 45) secured to the second support and configured to change the amount of light detected by the light detector based on the direction of flow of air within the second nostril.