Low Flow Blood Chamber with Elongated Cavity
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Solution Overview
Problem
Existing optical blood monitoring systems are not suitable for low blood flow applications, such as those with flow rates between 10 to 500 ml/min, as they tend to cause clotting and hemolysis, and are not compatible with existing sensor clip assemblies and control systems.
Innovation Solution
A low flow blood chamber with a flat, elongated internal blood flow cavity and oval-shaped perimeter edges, maintaining consistent dimensions with conventional chambers, ensuring non-laminar flow and compatibility with existing systems, eliminating the need for turbulence posts and allowing for easy installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional blood chamber design is used for low flow rates (10-500 ml/min), then the chamber can be compatible with existing sensor assemblies, but the blood flow becomes laminar causing clotting and hemolysis
Solution Approach 1:
The invention transitions from a conventional circular cross-section blood chamber to an elongated rectangular cross-section design. This dimensional change creates a longer blood flow path relative to the width, ensuring that blood flows through the entire chamber length and passes uniformly through the viewing area, thereby preventing laminar flow-induced clotting and hemolysis while maintaining compatibility with existing optical sensor assemblies
Solution Approach 2:
The invention introduces rounded corners at the four corners of the rectangular blood flow cavity. This curvature modification eliminates sharp edges that could cause blood cell damage (hemolysis) during flow, while maintaining the overall elongated rectangular shape that ensures homogeneous flow distribution through the viewing area
2Reliability
If turbulence posts are added to create non-laminar flow, then blood flow homogeneity improves, but device complexity increases
Solution Approach 1:
The invention removes the need for turbulence posts and other flow-disrupting structures by relying on the geometric configuration of the elongated rectangular chamber itself. The extended length and rounded corners naturally promote homogeneous flow without requiring additional components, thereby simplifying the overall device structure while maintaining reliable blood flow characteristics
Solution Approach 2:
The invention changes the geometric parameters of the blood chamber from a compact circular or square shape to an elongated rectangular shape with specific length-to-width ratios. This parameter change fundamentally alters the flow dynamics, creating naturally homogeneous flow patterns without requiring additional turbulence-inducing structures
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 solution provides consistent, non-laminar homogeneous blood flow without clotting or hemolysis issues at low flow rates, ensuring accurate hematocrit and oxygen saturation measurements, and is compatible with existing sensor clip assemblies and control systems.
Implementation Method 1
Multiple wavelengths of visible and infrared light are directed through the blood chamber and the patient's blood flowing through the blood chamber, and a photodetector measures the resulting intensity of light at each wavelength. The preferred wavelengths are about 810 nm (e.g. 829 nm), which is substantially isobestic for red blood cells, and about 1300 nm, which is substantially isobestic for water.
Implementation Method 2
a photodetector measures the resulting intensity of light at each wavelength
Implementation Method 3
The blood chamber comprises a molded, clear polycarbonate chamber body which includes an integral viewing lens on one side of the blood flow cavity
Data Source
AI summary
A low flow blood chamber for optically monitoring blood flowing through extracorporeal tubing has a flat elongated blood flow cavity but preserves the circular viewing area of conventional blood chambers. The blood chamber provides consistent, mixed flow through the blood cavity even at low blood flow rates, e.g. 10 to 500 ml/min., while maintaining certain dimensional characteristics of conventional blood chambers.