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Guidewire Final Presentation Apr 12
1. Gastro-Jejunal Feeding Tube Guide Wire for Infants Dr. RiadRahhal, Director, Pediatric Gastroenterology Fellowship Program University of Iowa Children's Hospital Department of Pediatrics ArunanArivalagan, Ahmad El-Hattab, Sean Ephraim, Ryan Hoeman Biomedical Engineering, University of Iowa, Iowa City, IA Toby Donjakowski, Medical Device Specialist
2. Gastro-jejunal procedure What is it? Placement of feeding tube into the patient’s jejunum Addresses infants that cannot swallow
25. Looking Ahead More testing Biocompatibility Paper work Confidentiality agreements patenting FDA approval
Notas del editor
UPDATE:-Broke down the procedure steps into different slides
A force versus position test was implemented. Initially, we had envisioned a number of different tests that would investigate the same phenomenon – the behavior of the wire as it moved through the feeding tube. We envisioned velocity testing under constant loading, and force testing under constant velocity. These tests proved quite difficult to conduct reliable, and the results varied to the extend that no statistically significant trends were observed. The test that was eventually carried out with a force gage and a way to secure the feeding tube was simple and produced meaningful results that we will discuss in detail shortly.
After modifying the testing methods to make testing simpler, we found that The results of the investigation are seemingly contradictory to the hypothesis. What we expected initially as seen on the previous slide, was that the force to move the wire out of the tube would increase at the valve. Our results show otherwise, with the forces being maximal at the main body of the feeding tube. There are several possible reasons for this, one of them being the fact testing environment did was not identical to the practical one. This leads us to speculate that there are many factors that affect the forces required to move the guidewire that were absent in our investigation. For instance, by keeping the feeding tube completely straight, we wanted to ensure that we were studying only the effect of the geometrical aspects of the wire itself on the forces. In reality, the geometry of the feeding tube inside the infant is likely to have a greater effect on these forces than we had originally anticipated. It is also likely that the region where the greatest exertion is needed occurs in areas of large geometric change inherent in the position of the wire. Another limitation of the investigation is that sufficient and homogeneous lubrication of the inner membrane of the feeding tube was difficult to achieve. Additionally, the lubricant used tended to coagulate after a short period of time, and as clots accumulated in the feeding tube, they seemed to increase friction, thereby incrementally reducing the reliability of subsequent tests carried out on each tube. This may account for the differences in the forces within he main boy of the feeding tube, wherein frictional and occlusive forces are expected to be constant throughout. In the surgical setting, non-homogenieties in the lubricated inner area of the tube may be a realistic problem that contributes to the problem we are attempting to address herein. However, lubricant coagulation is not something that was reported to us by Dr. Rahhal, although he has indicated that he uses water or glycerin solution for a lubricant. Our prototype has demonstrated that it requires less force to remove from the feeding tube, which moves us closer to achieving our goal. This constitutes a partial fulfillment of out hypothesis for this test. Valvular contact with the guidewire tip as the main source of the damaging forces to wire was largely an assumption that the results of this investigation seem to contend. It may be that the reason the valve did not exert the force that we expected to observe on the wire is that it is a rather compliant structure and probably offers little resistance to the motion of the wire.ConclusionWe may need to modify our tests further to include factors that are present in the surgical setting. We may incorporate curvature of the feeding tube, and perhaps find a lubricant that has less tendency to coagulate. The tests results indicate that the problem arises due to inadequate lubrication of the feeding tube as well as excessive diameter of the tip.
