Embedded Files
Medical Anesthesia Drug Delivery
___________________________________________________________________________________________________________________________________________
Pako Barba | Jamie Beasley | Rene Falquier | Michael Ix
Sponsored by: Dr. Benjamin Beal, UC San Diego School of Medicine
.
.
MAE156B: Fundamental Principles of Mechanical Design II | Spring 2014
Department of Mechanical and Aerospace Engineering | Jacobs School of Engineering | University of California, San Diego
___________________________________________________________________________________________________________________________________________
.
.
Figure 1: CAD of Final Design
.
Figure 2: Assembly of Final Design
.
Video 1: Medical Anesthesia Drug Delivery Project Demonstration
___________________________________________________________________________________________________________________________________________
Project Background
This project aims to improve the patient experience in the context of a Local Anesthetic Nerve Block (herein referred to simply as "Nerve Bock") procedure. Nerve Block procedures are used to anesthetize a local body area, such as a thigh, by targeting nerves of interest with an anesthetic drug and therefore anesthetizing the area. This allows other procedures to take place with no pain and minimal discomfort to the patient.
This project aims to improve the patient experience in the context of a Local Anesthetic Nerve Block (herein referred to simply as "Nerve Bock") procedure. Nerve Block procedures are used to anesthetize a local body area, such as a thigh, by targeting nerves of interest with an anesthetic drug and therefore anesthetizing the area. This allows other procedures to take place with no pain and minimal discomfort to the patient.
Nerve Block procedures are currently a two person operation requiring an anesthesiologist and an assistant. As is shown in the figure to the left, the anesthesiologist will use one hand to hold an ultrasound probe in place and the other to manipulate a needle through which anesthetic drug is injected. The ultrasound permits the anesthesiologist to see where the needle is in relation to the nerve they are attempting to target and therefore manipulate the needle accordingly, a screenshot of what the anesthesiologist sees through the ultrasound monitor is shown in the figure to the right. The anesthesiologist instructs the assistant to begin drug infusion when the needle is in the correct position and instructs an end to the procedure when the correct amount of drug has been injected into the area.
Nerve Block procedures are currently a two person operation requiring an anesthesiologist and an assistant. As is shown in the figure to the left, the anesthesiologist will use one hand to hold an ultrasound probe in place and the other to manipulate a needle through which anesthetic drug is injected. The ultrasound permits the anesthesiologist to see where the needle is in relation to the nerve they are attempting to target and therefore manipulate the needle accordingly, a screenshot of what the anesthesiologist sees through the ultrasound monitor is shown in the figure to the right. The anesthesiologist instructs the assistant to begin drug infusion when the needle is in the correct position and instructs an end to the procedure when the correct amount of drug has been injected into the area.
Project Objective and Functional Overview
Currently, one of the larges risks in such a procedure is that of an intraneural injection, defined as an injection directly into a nerve as opposed to it's immediate vicinity. This can cause permanent nerve damage and therefore
lasting consequences to a patient's well being. Currently, intraneural injections are sparsely documented but it has been reported that a build up of pressure can be felt at the syringe when such an injection is taking place. However, the pressures associated with these injections are not well documented. This project was inspired by the necessity of documenting intraneural pressures for future medical reference and the desire to put the control of the entire procedure in the hands of a single anesthesiologist.
Functionally, the system aims to replace the assistant with a Syringe Pump that is controlled by a Handheld Flow Control Device. This device will be held in one hand by the anesthesiologist and will allow them to manipulate the drug flow rates via a user interface such as a joystick. Furthermore, the Handheld Flow Control Device would have to securely hold a Braun 17 Gage Tuohy (hollow hypodermic) Needle in place so as to be able to inject and remove the needle from a patient. An ergonomic concept prototype of the Handheld Flow Control Device held by Dr. Beal can be seen in the figure to the right. The system must also incorporate a Pressure Transducer to sense pressures in the system and replace the tactile feedback of the person manipulating the syringe. Finally the system must include a Control Box housing a microprocessor to process signals from the Handheld Flow Control Device, Syringe Pump and Pressure Transducer and relay them to screens that would display both live pressure readouts and infused drug volume readouts.
Overview of Final Design
Overview of Final Design
The objective of the project was to design and manufacture a functional prototype for an Anesthesia Drug Delivery System for proof of concept purposes and basic research and documentation. The system had the overall objective of giving the anesthesiologist exclusive control over the procedure. This objective was to be met by placing the ability to manipulate the needle placement as well as infusion and withdrawal flow rates in a single hand. This would thus leave the other hand free to manipulate the ultrasound probe. Additionally, the system would need to provide the anesthesiologist with live readings of injected drug volume and system pressure so they can make decisions based on their professional training.
.
Figure 5: Annotated Photograph of Final Design
Our Final Design consists of four main modules: Control Box, Syringe Pump, Handheld Flow Control Device, and the Pressure Transducer. The control box is an off-the-shelf unit with a customized face plate and inner component shelves for securing of electronics. The screens and button layout was designed to facilitate user interface and minimize the amount of time required to prepare the system for a procedure. The Syringe Pump is also an OEM unit that matches our functional requirements for flow rates and processor-communication parameters. The Handheld Flow Control Device is a custom design incorporating feedback from multiple ergonomic concept prototype iterations as well as feedback from multiple sensor interfaces. Finally, the Pressure Transducer was an off the shelf medical grade unit originally designed for intravenous pressure monitoring. The pressures encountered by the system were outside the design specifications of the transducer. As such the device had to be adapted by calibration and engineering analysis to perform as per the functional requirements set by our sponsor. The creation of a model to generate P2 is outlined below.
Our Final Design consists of four main modules: Control Box, Syringe Pump, Handheld Flow Control Device, and the Pressure Transducer. The control box is an off-the-shelf unit with a customized face plate and inner component shelves for securing of electronics. The screens and button layout was designed to facilitate user interface and minimize the amount of time required to prepare the system for a procedure. The Syringe Pump is also an OEM unit that matches our functional requirements for flow rates and processor-communication parameters. The Handheld Flow Control Device is a custom design incorporating feedback from multiple ergonomic concept prototype iterations as well as feedback from multiple sensor interfaces. Finally, the Pressure Transducer was an off the shelf medical grade unit originally designed for intravenous pressure monitoring. The pressures encountered by the system were outside the design specifications of the transducer. As such the device had to be adapted by calibration and engineering analysis to perform as per the functional requirements set by our sponsor. The creation of a model to generate P2 is outlined below.
Overview of Performance Results
Overview of Performance Results
Pressure Sensing Model
Pressure Sensing Model
System:
The disposable pressure transducer was placed close to the syringe, as shown in the figure below.
The pressure of interest is Pressure P2, at the end of the needle
Steps were taken to parameterize the extended Bernoulli equation to determine P2 as a function of P1, a change in area term, a height term, and a head loss term
P1 - Calibration of Transducer to verify linear outputs for range of interest (-1:30psi)
Head Loss (pHL) - Performed experiment to inject fluid into atmosphere while maintaining all other terms constant to find the head loss
Height change (pgh) - changes in height accounted for by setting a reference height using tare button on handheld and incortporating it into the code
Parameterization of these values returned P2 as a function of P1
Figure 6: System schematic showing Syringe, tubing, needle, and pressure transducer
Experiment Performed: Incorporated a reference transducer at far end of system as shown below to gather approximately true readouts and compare with calculated pressures
Figure 8: Results of experiment
Experiment Results:
Model consistently underestimates actual pressure. Average error: 7.02% Maximum error 11%
Source of offset unknown
Flow and Pressure Control Performance
Experiment performed to verify human-software-display feedback loop
Process: The control box display would prompt a flow rate, and the user would attempt to match the flow rate using the handheld device. After matching the flow rate prompted and holding the match for 3 seconds, another flow rate was prompted and the process was repeated
Results: Experiment indicates that information displayed on the screen can effectively be used to complete a feedback loop
Figure 7: Experiment setup with Omega PX26 placed at other end
Page updated
Report abuse