Minimally Invasive Surgery and Interventional Techniques
Department of Biomechanical Engineering - Delft University of Technology
Contact Dennis van Gerwen
Dr. John J van den Dobbelsteen
Loss-Of-Resistance Simulator for Epidural Anesthesia Training
24 April 2013


Epidural anesthesia (a.k.a. de ruggenprik, depicted in Fig.1) is a form of regional anesthesia that is very common for pain relief during labor and also for a large variety of clinical interventions. The technique involves the injection of an anesthetic solution into the epidural space, close to the spinal cord. This is done using a large needle (1.7mm diameter, 8 to 15cm length) which is inserted into the epidural space.


Epidural procedure with LOR technique

Figure 1: Epidural anesthesia with the Loss-Of-Resistance technique


Getting this needle in the right place is not without risk, because it is inserted directly towards the spinal cord. Even a small overshoot (a few mm) can cause damage to the meninges or even to the spinal cord itself. Moreover, there is no visual feedback of the distance between the needle tip and spinal cord: The clinician is forced to rely solely on his/her sense of touch.

There are two main sources of touch-information that are used to estimate the needle position, one being the force required to advance the needle, and the other being Loss-Of-Resistance (LOR) to injection.

While the needle tip is surrounded by muscle or ligament, injection of a fluid will be difficult, i.e. the clinician experiences resistance to injection. However, as soon as the tip enters the epidural space, this resistance to injection is lost. Thus, Loss-Of-Resistance is an indication that the needle has entered the epidural space.

Together with Erasmus MC, we are developing a virtual-reality training simulator that teaches clinicians how to perform this procedure without putting real patients at risk. The epidural needle insertion simulator (Fig. 2) reproduces the force required to insert the needle, and allows insertion in different directions. The next step in the development is to include a Loss-Of-Resistance module.


Epidural needle insertion simulator

Figure 2: The epidural needle insertion simulator



Your assignment is to develop, implement, and evaluate a Loss-Of-Resistance module that is integrated with the existing simulator.

This LOR-module has to be able not only to control the injection pressure, but also to allow a reverse flow of both water and fake-blood. An experimental evaluation study of the resulting prototype is also part of the assignment. 

In this assignment you will need to cooperate closely with our clinical partners, and your work will lay the foundation for future clinical research.  

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