Micro-laser Finger Cuff for Neonatal Blood Pressure Measurement
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Solution Overview
Problem
Current finger cuff designs for non-invasive blood pressure monitoring using the volume clamp method face limitations, particularly with neonates and infants due to reduced light absorption and the tradeoff between optical device size and bladder inflation, leading to decreased system performance.
Innovation Solution
The use of a micro-laser and detector within the finger cuff, optionally with a reflector or multiple pairs, to enhance optical signal path length and accuracy, improving signal detection and bladder pressure control for precise blood pressure measurement across a wider range of patients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single LED and photodetector are used in the finger cuff, then the device structure is simple, but the optical signal path length is insufficient leading to decreased measurement precision especially in neonates and infants
Solution Approach 1:
The patent introduces a reflector to create an optical path that travels through the tissue multiple times (transmission-reflection-transmission), effectively increasing the optical path length in the dimension of light propagation without increasing the physical distance between LED and photodetector. This multi-pass optical path enhances light absorption by tissue while maintaining compact device structure.
Solution Approach 2:
The reflector acts as an intermediary element that redirects the optical signal back through the tissue, allowing the light to interact with the tissue multiple times. This intermediary component enables extended optical path length without requiring larger separation between light source and detector, thereby improving measurement precision in small patients.
2Measurement precision
If the optical devices (LED and photodetector) are placed in the middle of the bladder, then the alignment of transmitted and received signal is improved, but the bladder inflation and deflation capability is compromised
Solution Approach 1:
The patent divides the finger cuff into distinct functional zones: an optical sensing zone containing the LED, photodetector, and reflector, and a pneumatic zone containing the bladder. This segmentation allows the optical components to be optimally positioned for signal detection while the bladder maintains its inflation/deflation capability without interference from optical device placement.
Solution Approach 2:
The reflector serves as a mediator that enables the optical path to be configured independently of the bladder position. By using the reflector to redirect light, the system achieves proper optical alignment without requiring the optical devices to be positioned in the middle of the bladder, thus preserving bladder functionality.
3Adaptability or versatility
If the finger cuff is designed for adult tissue, then the optical signal absorption is sufficient, but the device performance decreases when used on neonates and infants with smaller tissue
Solution Approach 1:
The multi-pass optical path created by the reflector compensates for the reduced tissue thickness in neonates and infants. By increasing the effective optical path length through multiple transmissions and reflections, the system achieves sufficient light absorption even in small patients, thereby extending adaptability across different patient sizes while maintaining measurement precision.
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 implementation of micro-lasers and detectors in the finger cuff enhances signal coherence and focus, improving blood pressure measurement accuracy and suitability for various patient sizes, including neonates, by increasing signal path length and maintaining optimal bladder inflation.
Implementation Method 1
an optical transmitter to generate a signal at a desired wavelength that passes through a biological tissue (e.g., a finger) and a detector that detects the amount of light after passing through this tissue
Implementation Method 2
a reflector, wherein, the micro-laser emits a signal through the patient's finger, and the signal is reflected by the reflector back through the patient's finger to the detector
Data Source
AI summary
Disclosed is a finger cuff connectable to a patient's finger to be used in measuring the patient's blood pressure utilizing the volume clamp method. The finger cuff may comprise: a finger cavity to receive the patient's finger; a micro-laser and a detector to measure a pleth signal; a bladder mountable within the finger cavity, wherein the patient's finger received in the finger cavity abuts against the bladder; and a processor. The processor may be configured to control pressure applied by the bladder to the patient's finger based upon measuring the pleth signal received from the detector and the micro-laser to keep the pleth signal approximately constant to replicate the patient's blood pressure to implement the volume clamp method and to measure the patient's blood pressure.