TEST METHOD OF HIGH-SPEED ON-OFF VALVE DYNAMIC CHARACTERISTICS

According to the valve port features of high speed on-off valve and its actions, the valve port can be simplified into an a-type half bridge construction. A method that tests the dynamic characteristics of the high speed on-off valve by the output pressure signal of the a-type half bridge is proposed. Having analyzed the factors related to the dynamic characteristics of an a-type half bridge, a rule for designing the outlet chamber＇s volume is worked out. According to the rule, a test stand is built to test the self-developed high-speed on-off valve. From the test results, it can be seen that with the outlet chamber＇s volume controlled by the rule the rise time of the pressure signals driven by signals with different frequencies changes very little. The test results conform to the simulation results, which nroves the correctness of the method.

Ileocecal valve dysfunction in small intestinal bacterial overgrowth: A pilot study

AIM: To explore whether patients with a defective ileocecal valve (ICV)/cecal distension reflex have small intestinal bacterial overgrowth. METHODS: Using a colonoscope, under conscious sedation, the ICV was intubated and the colonoscope was placed within the terminal ileum (TI). A manometry catheter with 4 pressure channels, spaced 1 cm apart, was passed through the biopsy channel of the colonoscope into the TI. The colonoscope was slowly withdrawn from the TI while the manometry catheter was advanced. The catheter was placed across the ICV so that at least one pressure port was within the TI, ICV and the cecum respectively. Pressures were continuously measured during air insufflation into the cecum, under direct endoscopic visualization, in 19 volunteers. Air was insufflated to a maximum of 40 mmHg to prevent barotrauma. All subjects underwent lactulose breath testing one month after the colonoscopy. The results of the breath tests were compared with the results of the pressures within the ICV during air insufflation. RESULTS: Nineteen subjects underwent colonoscopy with measurements of the ICV pressures after intubation of the ICV with a colonoscope. Initial baseline readings showed no statistical difference in the pressures of the TI and ICV, between subjects with positive lactulose breath tests and normal lactulose breath tests. The average peak ICV pressure during air insufflation into the cecum in subjects with normal lactu-lose breath tests was significantly higher than cecal pressures during air insufflation (49.33 ± 7.99 mmHg vs 16.40 ± 2.14 mmHg, P = 0.0011). The average percentage difference of the area under the pressure curve of the ICV from the cecum during air insufflations in subjects with normal lactulose breath tests was significantly higher (280.72% ± 43.29% vs 100% ± 0%, P = 0.0006). The average peak ICV pressure during air insufflation into the cecum in subjects with positive lactulose breath tests was not significantly different than cecal pressures during air insufflation 21.23 ± 3.52 mmHg vs 16.10 ± 3.39 mmHg. The average percentage difference of the area under the pressure curve of the ICV from the cecum during air insufflation was not significantly different 101.08% ± 7.96% vs 100% ± 0%. The total symptom score for subjects with normal lactulose breath tests and subjects with positive lactu-lose breath tests was not statistically different (13.30 ± 4.09 vs 24.14 ± 6.58). The ICV peak pressures during air insufflations were significantly higher in subjects with normal lactulose breath tests than in subjects with positive lactulose breath tests (P = 0.005). The average percent difference of the area under the pressure curve in the ICV from cecum was significantly higher in subjects with normal lactulose breath tests than in subjects with positive lactulose breath tests (P = 0.0012). Individuals with positive lactulose breath tests demonstrated symptom scores which were significantly higher for the following symptoms: not able to finish normal sized meal, feeling excessively full after meals, loss of appetite and bloating. CONCLUSION: Compared to normal, subjects with a positive lactulose breath test have a defective ICV cecal distension reflex. These subjects also more commonly have higher symptom scores.