Medical Device with Misaligned Cannula and Controlled Retraction
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Solution Overview
Problem
Existing medical devices for percutaneous or venous access often face issues with accidental cannula tip exposure to healthcare operators, leading to infection risks and unintended cannula detachment during use, causing fluid spills, pain, noise, and vibration, due to rapid return mechanisms and potential activation during cannula insertion.
Innovation Solution
A medical device with a rigid cannula-holder and a recall mechanism using a compression spring, slider, and inclined plane to control cannula retraction, ensuring the cannula is securely housed within the device after use, preventing accidental exposure and maintaining safety without flexible components that require operator force for activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a preloaded resilient element (spring) is used to automatically move the protective body or retract the cannula, then the safety function is improved and automatic operation is achieved, but the return speed becomes excessive causing fluid spurts, patient pain, noise, and vibration
Solution Approach 1:
The patent transforms the static spring mechanism into a dynamic controlled-release system. The spring remains preloaded but its action is modulated by a blocking element that controls the timing and speed of cannula retraction. This allows the system to maintain automation while regulating the return speed to avoid harmful effects.
Solution Approach 2:
The blocking element acts as an intermediary between the spring and the cannula-holder. It mediates the force transmission from the spring, controlling when and how the cannula retracts. This intermediary component prevents direct uncontrolled action of the spring, thereby reducing excessive speed and associated harmful effects.
2Extent of automation
If a resilient spring mechanism is used for cannula retraction, then automatic safety function is improved, but unintended activation during cannula insertion may occur
Solution Approach 1:
The blocking element is pre-positioned to prevent spring action during insertion. This preliminary blocking action ensures that the spring mechanism cannot activate unintentionally during cannula insertion, while still being ready to activate automatically after use when the blocking element is removed.
Solution Approach 2:
The system incorporates a feedback mechanism where the blocking element's position determines whether the spring can act. The blocking element responds to operational conditions (insertion vs. post-use), providing feedback control that prevents unintended activation while enabling proper automatic retraction when appropriate.
3Ease of operation
If flexible plastic components are used in the device body, then ease of insertion and skin breathability are improved, but device structural integrity and precision may be compromised
Solution Approach 1:
The patent applies different material properties to different parts of the device. Flexible plastic components are used where ease of insertion and skin contact are needed (fins, body), while rigid materials are used for precision components (cannula-holder, blocking element, slider). This local differentiation allows each component to optimize its function without compromising overall device precision.
Solution Approach 2:
The device is segmented into flexible components (body, fins) and rigid components (cannula-holder, blocking element, slider). This segmentation allows the flexible parts to provide ease of insertion while the rigid parts maintain manufacturing precision and proper alignment, particularly for the misaligned cannula configuration.
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 controlled and safe cannula retraction, reducing the risk of infection and fluid spills, while ensuring the cannula tip remains inaccessible, maintaining protection characteristics over time, and simplifying production and assembly for reliable and cost-effective operation.
Implementation Method 1
The movement is generated by a compression spring (26) disposed between the first end (2A) of the first casing (20) and a collar (29) provided on the first end part (7) of the cannula-holder (8)
Implementation Method 2
a protuberance (53) provided on the slider (24) and sliding on an inert part (88) of the cannula-holder (8) before sliding on a blocking tooth (35) of the cannula-holder (8), which tooth (35) co-operates with the inclined side (32)
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A medical device (1) for percutaneous or venous access, for the purpose of administering or collecting a fluid to or from a patient, comprising a tubular body (2) with an internal cavity (25), from which a cannula (4) extends in a first position of work, said cannula being supported by a distal end (7) of a cannula-holder (8), said cannula-holder (8) movable within the cavity (25) of said body (2) of the device (1) by means of a resilient thrust element (26), such as to propulse the cannula (4) inside the tubular body (2), actuation means (24) permitting this movement, which means are associated with the body (2) of the device (1), and cooperate with actuation counter-means (35) integral with said cannula-holder (8). The cannula (4) has its longitudinal axis (W) disposed inclined relative to the longitudinal axis (K) of the tubular body (2), said cannula-holder (8) being substantially rigid.