Infusion Device Startup Routine for Syringe Piston Control
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Solution Overview
Problem
Existing infusion devices face challenges in efficiently starting the infusion process due to potential delays and risks of unwanted bolus delivery, as they rely on unreliable force or distance criteria to determine when the piston begins to move, especially with syringes that may stick after prolonged rest.
Innovation Solution
Implementing a startup routine where the pusher device is initially moved at a first velocity, and upon detecting a drop in measured force indicating piston movement, switched to a second velocity corresponding to the targeted flow rate, thereby overcoming system play and elasticity while preventing initial bolus delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the pusher device is initially moved at an increased velocity to overcome system play and elasticity, then the delay time before infusion starts is reduced, but the risk of uncontrolled bolus delivery increases
Solution Approach 1:
The system continuously monitors the force acting on the piston during the quickstart phase and uses this feedback to detect when the piston begins to move. When a predetermined force threshold is exceeded, the system automatically reduces the pusher velocity from initial to operational speed, preventing bolus delivery while minimizing delay.
2Manufacturing precision
If the pusher device is moved at the targeted pushing velocity from the start, then the flow rate is accurate from the beginning, but a long delay time occurs before fluid delivery starts
Solution Approach 1:
The system performs a preliminary quickstart phase where the pusher device is accelerated at a higher velocity to rapidly overcome system play and elasticity. This preliminary action brings the piston close to movement quickly, after which the velocity is reduced to achieve precise flow rate control once fluid delivery begins.
3Device complexity
If a predetermined maximum distance is used to determine when infusion starts, then the control method is simple, but the estimation may be inaccurate especially when syringes stick after prolonged rest
Solution Approach 1:
The system replaces distance-based detection with force-based detection. Instead of measuring how far the pusher has moved, the system monitors the force acting on the piston in real-time. This substitution provides more accurate detection of piston movement onset, especially when syringes have stuck after prolonged rest, without significantly increasing system complexity.
4Device complexity
If force comparison with predetermined maximum force is used to estimate infusion start, then the method is straightforward, but the accuracy depends on syringe type and waiting time
Solution Approach 1:
The system dynamically adjusts the predetermined force threshold based on the waiting time since syringe installation. As the waiting time increases and the risk of piston sticking increases, the force threshold is adjusted accordingly. This dynamic adaptation maintains accurate infusion start detection across different syringe types and waiting periods while keeping the control method straightforward.
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 approach allows for a reliable and efficient quickstart of the infusion process, minimizing delays and the risk of unwanted bolus delivery by accurately determining when the piston starts moving and transitioning to the targeted flow rate.
Implementation Method 1
a sensing device outputting a sensing signal indicative of the measured force acting in between the pusher device and the piston of the syringe
Data Source
Figure 1
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AI summary
A method for operating an infusion device (1) for administering a medical fluid to a patient comprises: receiving a syringe (2) in a receptacle (11) of the infusion device (1); moving, using an electric drive device (141), a pusher device (12) in a pushing direction (P) for acting onto a piston (21) of the syringe (2) received in the receptacle (11); and obtaining, using a sensing device (171), a sensing signal indicative of a measured force (F) acting in between the pusher device (12) and the piston (21) of the syringe (2). Herein it is provided that, at the beginning of moving the pusher device (12) for acting onto the piston (21), a startup routine is executed in which in a first phase the electric drive device (141) drives the pusher device (12) to move at a first velocity (V0), and if by means of the sensing signal a drop in the measured force (F) acting in between the pusher device (12) and the piston (21) of the syringe (2) is observed, the electric drive device (141) is controlled to drive the pusher device (12) to move at a second velocity (V1) different than the first velocity (V0). In this way a method for administering a medical fluid to a patient is provided which allows for an efficient quickstart procedure.