Development of the micro-TOS system

A sensor compatible with the TOS-OR rSO₂ monitor (Fujita Medical Instrument) was shaped into a 250-mm rod (Figure 2) for use in a minimally invasive endoscopic surgery. A light source and a sensor were built into the tip of the stainless-steel rod at a 30° angle. An ultra-small infrared light-emitting diode (LED) light source and two types of infrared light sensors were placed at the tip of the rod. The tips of the sensors were covered with black resin for measurement of the intended targets under light shielding. Three wavelengths of light (770, 805, and 870 nm) were irradiated from the LED light source for measurement. They were received for measurement by a sensor 6 mm away from the source. By attaching this custom sensor to the bronchial wall, TOS could be measured at a depth of 4–5 mm from the surface of the bronchus. The device captured 10 continuous time series data every second. Validation testing of the micro-TOS system was performed using the small intestine of a live porcine, as the organ has a simple anatomical structure and it is easy to surgically control the blood flow. While blood flow through the intestinal serosa was maintained, the rSO₂ level was 80.7%±1.7%, but the rSO₂ level decreased to 29.4%±2.5% in the ischemic state. The blood vessels of the intestinal tract that we wished to evaluate were ligated, and both sides of the intestinal tract were blocked with clamp forceps to inhibit mucosal blood flow. We were then able to accurately determine the TOS of the intestinal wall of several millimeters (figure not shown).

The newly developed micro-TOS sensor and thoracoscopic tissue oxygen saturation measurement. (A) An extremely small-sized tissue oxygen saturation monitor was molded into a rod with a diameter of 8 mm and a length of 250 mm to be inserted through the access port during endoscopic surgery. (B) A near-infrared LED and a near-infrared sensor were built on the tip of the rod. (C) When the surrounding area was covered with black resin and brought into close contact with the tissue, tissue oxygen saturation could be measured in a state where local light was shielded. UL, upper lobe of right lung; ML, middle lobe; LL, lower lobe; MLB, middle lobe bronchus; BS, bronchial stump (the location of the cut and stapled inferior trunk).