Abstract: In accordance with illustrative embodiments of the present invention as disclosed herein, a retractable blade knife particularly adapted for use as a surgical scalpel or the like includes a thin metal blade positioned in a cavity inside a handle and being movable between an extended position and a retracted position. In the extended position the blade is releasably locked to the handle in response to resilience of the blade caused by flexure thereof from its relaxed condition. In one embodiment the relaxed state of the blade is slight curved, and in another embodiment, such state is substantially flat. A shoulder that locks the blade in extended position is released by pressing on a pin that extends through a slot in the handle, and the pin, also is used to shift the blade longitudinally.

Abstract: A method and apparatus for placing a nasogastric tube into a patient by inserting and releasably anchoring a pH detector in the bore of the tube adjacent the distal end. The detector is connected through the proximal end of the tube to a pH monitor. The tube and detector are inserted into the patient while monitoring the measured pH of the detector for determining the placement of the tube. After placing the tube, the detector is released from the bore of the tube and removed from the nasogastric tube while leaving the tube in the patient. The detector is releasably anchored by inflating a balloon connected to the detector.