The sphincteric function of the crural diaphragm has been difficult to measure in humans. The authors recently reported the use of a Dent sleeve device to measure esophagogastric junction pressure during contraction of the crural diaphragm. However, the major limitation of the conventional sleeve device is its slow response rate, and sustained diaphragmatic contractions of 6-8 seconds must be induced to measure the true pressure. In this article, the principles of a reverse-perfused sleeve device and the theoretical basis for its fast response rate are reported. The reverse-perfused sleeve is validated in an in vitro model of the lower esophageal sphincter. Furthermore, in vivo studies were performed in seven healthy human subjects. Standardized Muller maneuvers and straight-leg raises were performed to induce diaphragmatic contractions. Pressure increases of 50-150 mm Hg during diaphragmatic contractions were attained in less than 1 second. The delay between the actual contraction of the diaphragm as measured by simultaneously recorded crural diaphragm electromyography and pressure recorded by the sleeve was only 0.25-0.50 seconds. Increasing the rate of infusion of the sleeve from 0.5 to 1.0 mL/min did not further improve the response rate of the reverse perfused sleeve. It was concluded that the reverse-perfused sleeve is a considerable improvement over the conventional sleeve for quantitating the sphincteric function of the crural diaphragm. The role of the crural diaphragm in reflux esophagitis may be easily investigated using a reverse-perfused sleeve device.