Training facilities in gastrointestinal endoscopy: an animal model as an aid to learning endoscopic ultrasound.

Apart from dedicated fellowships, endoscopic ultrasound (EUS) training comprises "informal" methods, including EUS courses and the use of animal models. We have tried to determine the usefulness of a "hands-on" experience with a live animal model as a teaching strategy for EUS training. In 1997 and 2000 the American Society for Gastrointestinal Endoscopy (ASGE) sponsored hands-on EUS workshops using a live porcine model and participants in these courses were asked to complete a questionnaire about the course (2 years after the 1997 workshop and immediately after the 2000 workshop). The main outcome measurements were the usefulness and quality of the overall course and of the hands-on component in particular, and the effect on EUS practice patterns. Twenty of 38 attendees (53 %) responded to the survey administered 2 years after the 1997 course: 95 % thought the overall course was useful and 85 % valued the hands-on portion; 60 % of respondents had either started performing EUS or, if already experienced in EUS, had increased the number of EUS examinations and/or the complexity of EUS procedures they performed. Of the 34 participants who were at the 2000 ASGE course, over 90 % thought that the course enhanced their EUS skills and 88 % believed that they would be likely to perform EUS in the future. The study was limited in that it did not account for other methods of EUS training that could affect EUS practice patterns and also by the fact that not all the 1997 course participants responded to the questionnaire. In conclusion, live animal models may be a useful adjuctive method for learning EUS skills for the novice or the less experienced endosonographer.

Simultaneous endoluminal sonography and manometry to assess anal sphincter complex in normal subjects.

The purpose of this study was to use simultaneous anal manometry and high-frequency endoluminal ultrasonography (EUS) to determine the relationship between resting anal pressure and cross-sectional area of the internal and external anal sphincters. Eleven normal subjects underwent simultaneous anal EUS and manometry using catheters containing both pressure ports and ultrasound transducers. Resting pressure and cross-sectional area of the sphincters were made throughout the anal sphincter complex. The length of the internal anal sphincter (IAS) by sonography (27+/-5 mm) was significantly less than the length of the high pressure zone (HPZ) by manometry (44+/-8 mm; P < 0.001). Maximum IAS cross-sectional area (CSA) occurred 10+/-6 mm proximal to the peak resting pressure. The resting anal pressure correlated with external anal sphincter (EAS) CSA (r = 0.77), but not with IAS CSA (r = -0.17). The sum of EAS CSA and IAS CSA correlated strongly with resting pressure (r = 0.85). In conclusion, the IAS is shorter than the HPZ, with a significant distance separating maximum IAS CSA from peak resting pressure. The sum of the IAS and EAS CSAs, but not that of the IAS alone, correlated with resting pressure. Thus, this study suggests that the EAS, in addition to the IAS, contributes to resting anal pressure.

Prediction of the kinetics of disappearance of sulfur hexafluoride and perfluoropropane intraocular gas bubbles.

Intravitreal gases are useful in treating complicated retinal detachments by providing internal tamponade of retinal breaks. The geometry of the intraocular gas bubble and the kinetics of intraocular gas absorption determine the geometry and duration of internal tamponade of the retinal break. The authors derived a mathematical relationship based on a geometric model of the rabbit eye which allows calculation of the volume of an intraocular gas bubble from its observed meniscus height. When compared with actual measured bubble volumes, this technique was found to provide an accurate, noninvasive method for determining true intraocular gas volumes. Using this model, the absorption of nonexpansile concentrations of sulfur hexafluoride (SF6) and perfluoropropane (C3F8) were found to obey first-order kinetics. Both gases were found to have an intraocular half-life two to three times shorter in aphakic rabbit eyes after total vitrectomy than in phakic rabbit eyes with intact vitreous.