Previous studies on variable stiffness colonoscopes showed mixed results. Different methods of activating the variable stiffness function were used and might explain part of the controversy. To determine the most efficient way of activating the variable stiffness function, this study compared 3 methods (no activation, regular activation, activation on an as-needed basis) using 1 single type of pediatric variable stiffness colonoscope. Asymptomatic patients admitted for physical check-up at the Buddhist Dalin Tzu Chi General Hospital were included. A single endoscopist performed all of the colonoscopic examinations of patients under sedation using a variable stiffness pediatric colonoscope. Consecutive patients were randomized to undergo colonoscopy using 3 different methods of activating the variable stiffness function: no activation ("no" group), regular activation at descending colon ("regular" group), and activation on an as-needed basis ("as-needed" group). Completion rate, cecal intubation time, and use of adjunct measures were evaluated and compared among the 3 groups. Subgroup analysis by gender was also performed. Between January and July 2006, a total of 250 patients were enrolled. The completion rates of the examinations were 97.6%, 91.7% and 96.4% in the no, regular and as-needed groups, respectively (p = 0.17). The cecal intubation times were 5.6 +/- 2.6 minutes, 5.6 +/- 2.7 minutes and 6.2 +/- 2.3 minutes, respectively (p = 0.22). Multivariate logistic regression analysis showed that activation of the variable stiffness function regularly (odds ratio [OR], 0.53; 95% confidence interval [CI], 0.28, 0.98; p = 0.04) or on an as-needed basis (OR, 0.52; 95% CI, 0.28, 0.97; p = 0.04) were independent factors that were related with less use of abdominal pressure. When only women were considered, the completion rate was lower in the regular group (98.0%, 86.8% and 96.5%, p = 0.04). The use of abdominal pressure was more in the no group than the other 2 groups (56%, 34% and 33%, p = 0.03). When only men were considered, the cecal intubation time was longer in the as-needed group (4.6 +/- 1.4, 4.6 +/- 1.8 and 5.8 +/- 2.5 minutes, p = 0.02). The other outcomes were similar in both genders. The 3 different methods did not result in significantly different completion rates or cecal intubation times. However, activation of the variable stiffness function decreased the need for abdominal pressure. When males and females were considered separately, activation of the variable stiffness function on an as-needed basis in females was the only useful setting.
