Limb-Worn Pulse Oximeter Bone-Avoidance Alignment
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Solution Overview
Problem
Pulse oximetry measurements on sites other than the fingertip, such as the forearm or lower leg, face challenges due to larger pathlengths, bone structures, and movement, leading to inaccurate readings and misalignment of emitters and detectors.
Innovation Solution
A wearable patient monitoring device is designed to be worn on limbs, with emitters and detectors aligned to avoid bone collisions and secured by resilient members, using a housing that limits movement and includes a large area detector to improve signal reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If pulse oximetry measurements are taken on sites other than fingertip (such as forearm or lower leg), then the device can be worn on limbs for continuous monitoring, but the larger pathlengths and bone structures lead to inaccurate readings
Solution Approach 1:
The patent positions the emitter and detector at specific locations on the limb (between radial and ulnar bones for forearm, or between tibia and fibula for lower leg) to create a localized measurement path that avoids bone interference. This spatial differentiation allows the device to function on various limb locations while maintaining measurement accuracy by selecting optimal local measurement zones.
Solution Approach 2:
The patent transitions from traditional fingertip measurement to limb-based measurement by utilizing the dimensional space between bones (interosseous space). This dimensional change allows light to pass through tissue without bone interference, enabling wearable monitoring on limbs while maintaining signal quality and measurement accuracy.
2Measurement precision
If the emitter and detector are positioned to avoid bone structures, then measurement accuracy improves, but device alignment becomes more complex
Solution Approach 1:
The housing is pre-configured with the emitter and detector positioned at predetermined locations that correspond to optimal measurement zones on the limb. This preliminary positioning ensures that when the device is applied, the optical path automatically avoids bone structures without requiring complex real-time alignment adjustments by the user.
Solution Approach 2:
The housing design incorporates universal positioning features that work for different limb types (forearm with radius and ulna, or lower leg with tibia and fibula). This universal design allows the same device structure to achieve proper alignment on various limbs, simplifying the alignment process while maintaining measurement accuracy across different application sites.
3Measurement precision
If the device is secured tightly to the skin to prevent movement, then measurement accuracy improves, but patient comfort decreases
Solution Approach 1:
The housing incorporates flexible materials and thin film structures that can conform to the contours of the limb while maintaining secure contact. This flexibility allows the device to be snug enough to prevent movement and maintain alignment stability, while remaining comfortable for extended wear by adapting to the patient's anatomy rather than imposing a rigid structure.
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 device provides accurate physiological parameter measurements by maintaining alignment and secure contact with the skin, reducing movement-related errors and enhancing signal quality across larger pathlengths.
Implementation Method 1
The detector can sense the light after it passes through and is attenuated by the tissue and generate a signal indicative of the sensed light
Data Source
AI summary
The present disclosure describes example systems, methods, apparatuses, and medical devices for obtaining physiological parameter data from a wearable patient monitoring device. An example patient monitoring device can include an emitter and a detector. The emitter can emit light through tissue of a patient. The detector can sense the light after it passes through and is attenuated by the tissue and can generate a signal indicative of the sensed light. When the patient monitoring device is attached to or worn by the patient, the emitter and detector are aligned such that the light from the emitter travels through an opening between a first bone and a second bone of the patient prior to being sensed by the detector.