1 Esophageal Stricture Compliance Measuring Device Biomedical Engineering Design 200/300 William Stanford- Team Leader/BSAC Dan Frost – BWIG Tom Fleming – Communicator Client: Mark Reichelderfer, MD Department of Gastroenterology, UW Medical School Advisor: John Webster, Ph.D. Professor Emeritus, Department of Biomedical Engineering October 24, 20072 Table of Contents Abstract………………………………………………………………...…3 Background……………………………………………………………….3 Problem Statement………………………………………………………5 Design Requirements and Constraints…………………………….…6 Design Option 1……………………………………………………..…..7 Design Option 2………………………………………………….…..….9 Design Option 3…… ………………………………………………….11 Design Matrix………………………………………………………......11 Future Work…………………………………………………………….13 References………………………………………………………………153 Abstract Esophageal strictures occur in the lower esophagus just above the cardiac sphincter. The main cause of strictures is acid reflux disease but they can also be caused by cancer and genetics. Larger strictures cause the opening of the esophagus to shrink, making difficult to swallow. The goal of this project is create a device that can measure the compliance of esophageal strictures by measure the pressure of the stricture against the dilation balloon and the volume of liquid inside the balloon. LabView will be used to design a program that can display a real time pressure vs. volume graph from which compliance can be measured. In the future, this data will be used to analyze different esophageal strictures and better understand how they form and work. Background The esophagus (Figure 2) is the tubular structure connecting the throat to the stomach. A specialized muscle called the lower esophageal sphincter (LES, Figure 1) and located at the distal end of the esophagus regulates the Figure 2: Stomach and Esophagus (from: http://intmed.muhealth.org/gast/patient_resource/anatomy_function/esophagus.html) Figure 1: Lower Esophageal Sphincter (from:http://www.gicare.com/pated/eiegnmle.htm)4 passage of food and liquid into the stomach. When working properly, the LES relaxes to allow foods and liquids to pass into the stomach and then contracts to prevent stomach acids and the digested food to move back up the esophagus. Occasionally, the LES fails to contract properly and allows digestive enzymes and stomach acids to reflux into the esophagus. This acid reflux damages the tissue of the lower esophagus. When damage occurs frequently, repeated healing cycles cause scar tissue to build up in the esophagus. This scarring causes a narrowing of the esophagus called an esophageal stricture (Figure 3). About 70-80% of esophageal strictures are caused by this type of gastroephageal reflux (Vasudeva, 2006). Other causes of these strictures include the ingestion of corrosive substances like cleaning solution, damage caused by endoscopy, and infection by bacteria or viruses, but each of these accounts for only a small fraction of stricture occurrences. A person with an esophageal stricture will experience some difficulty swallowing, called dysphagia. In mild cases, this dysphagia is limited to the swallowing of solid foods, but in more severe cases even swallowing liquids can be extremely painful. The most common treatment method for these strictures is called balloon dilation (Figure 3). This procedure utilizes a balloon attached to a syringe via a narrow plastic tube. The balloon Figure 3: Balloon Dilation of an Esophageal Stricture5 is pushed through the esophagus and into the narrow stricture opening. Saline solution is then delivered to the balloon from the syringe to gradually widen the area of the stricture. Typically, the diameter stricture is widened anywhere from 5-20mm (Vasudeva, 2006). Though this procedure widens the stricture, there is a large rate of stricture recurrence, and any single patient may have to undergo this procedure many times in his or her lifetime. Most of the time this procedure is safe, but in some cases, the dilation can cause a perforation of the tissue of the esophagus. These cases of perforation can be very dangerous as they can lead to infections and even death. A study of the compliance (the change in volume per unit of applied pressure) of the esophageal stricture could provide valuable insight into the kinds of applied pressures that generally cause perforation. If compliance could be measured effectively, these dangerous cases could be minimized or even eliminated. Problem Statement Little work has been done with the compliance of esophageal strictures. If more was known about the compliance of different size strictures, doctors could categorize them and develop trends that would lead to more efficient treatment options. Currently, there are no devices on the market that measure the compliance of esophageal strictures. The objective of the client and the team is to create a device that can measure the compliance of esophageal strictures. The output of the device should provide a real time graph of compliance that can be viewed during the procedure and also be capable of altering the procedure team to any perforation of the esophagus that requires immediate action.6 Design Requirements and Constraints The device and the software used to display information while using it require some capabilities which are critical when monitoring what is happening during an esophageal dilation surgery. Quite simply, it must measure volume of saline that is being injected into the dilation balloon and also the pressure the balloon exerts on the esophagus. With this, it must then graph in real time these results, creating a tissue compliance curve that can be used by the physician to maintain a safe dilation process. This curve is an example of what our software may display to the physicians in real time. Eventually, the compliance data should be accurate to three significant figures past the decimal. Other design requirements have to do with maintaining the simplicity of the procedure for the physician, and not
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