A miniature extracorporeal circulation model for a rat is used to study the mechanism of pathophysiological changes during extracorporeal circulation. The miniature extracorporeal circulation model consists of an extracapillary blood flow type oxygenator, a roller pump and a tubing. In this study, the extracapillary blood flow type oxygenator for the miniature extracorporeal circulation model for a rat was developed and evaluated in in vitro experiments. Three types of oxygenators with different priming volume (Type A: 7ml; Type B: 5ml; Type C: 3ml) were prototyped. The gas exchange performance and pressure drop in each oxygenator were evaluated in in vitro experiments. These oxygenators were installed horizontally and vertically in order to evaluate the influence of blood flow in the oxygenator. As a result, O₂ gas transfer rate of the oxygenator Type C with the lowest priming volume of 3ml in vertical installation was higher than the reference value of AAMI. Furthermore, it was confirmed that the change in blood flow by installation direction of the oxygenator affects gas exchange performance. It is considered that the developed oxygenator Type C has the performance that can be used for the miniature extracorporeal circulation model for a rat.

Natural orifice translumenal endoscopic surgery (NOTES) is a minimally invasive surgery performed using an endoscope. However, this surgery is challenging for surgeons owing to the insufficient view of the operative field during the surgery. In this paper, a supporting tool system that enhances the field of view (FOV) of an endoscope is introduced. The developed tool is attached to the endoscope and inserted into the patient's abdominal cavity from the patient's mouth. The tool is mounted on the abdominal cavity using a magnet mounted on the outside surface of the body. When the tool is released from the endoscope, the arms of the tool, which have LEDs and a miniature camera, are opened. The FOV of the workspace are then enhanced by the camera and LEDs on the tool. The arms can be folded when the tool is reattached to the endoscope and thus recollected. A prototype of the tool was manufactured by metal and resin and its basic performance for a series of movements was confirmed using a pseudo abdominal cavity. The attached LEDs and camera enhance the FOV for endoscopy because the planar view of the forceps is also added. Further, the performance for attracting the tool by the magnet on to the abdominal wall was evaluated. The tool can be attached to an acrylic board with a maximum thickness of 24.7 mm using a Φ20 × 10 mm neodymium magnet. The maximum pressure was 19 × 10³ N/m², that was less than the value by which the skin was damaged. However, the attraction force is small and under 1.0 N for a board with thickness greater than 11.0 mm, which is estimated to be that of the human body. Using a support tool that can enhance the FOV of the surgical field has large potential to increase the usefulness, safety, and demand of NOTES surgery.