N Kobayashi

NIHON KOHDEN CORPORATION, Edo, Tōkyō, Japan

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Publications (4)3.01 Total impact

  • M Oura · N Kobayashi · S Yamamori · S Takeda · K Iwasaki · M Umezu
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    ABSTRACT: We have studied noninvasive devices for measuring total hemoglobin and hemoglobin derivatives such as carboxyhemoglobin (COHb) and methemoglobin (MetHb). A calibration procedure needs to be developed to evaluate or calibrate these devices and pulse oximeters for clinical practice. However, people and animals are sometimes exposed to risk when they are used for calibration. In this paper, we propose a new in vitro calibration system for a pulse photometer. This system has a novel double-layer pulsation flow-cell that incorporates both venous and arterial blood flow. Using the calibration system, we are able to measure the in vitro pulsatile optical density ratio (Phivt). The measured Phivt agrees well with the in vivo pulsatile optical density ratio (Phivi). This system simulates an in vivo environment with high accuracy and enables safe calibration. Consequently, the calibration system is able to standardize the performance and accuracy of pulse photometry.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2009; 2009:896-9. DOI:10.1109/IEMBS.2009.5334889
  • M Oura · N Kobayashi · S Takeda · K Iwasaki · M Umezu
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    ABSTRACT: We have developed an extremely compact mock circulation system. This system can simulate artery blood circulation and generate a pulse wave with a very small amount of blood. We were also able to measure the in vitro pulsatile optical density ratio (Phivt) using this system with a flow cell [1]. Results showed a difference between Phivt and the in vivo pulsatile optical density ratio (Phivi) for the same oxygen saturations. To explain this difference, we proposed a new flow-cell model that includes venous flow and arterial flow. Because these systems can simulate the in vivo environment with very accurately, they can be applied to various pulse spectrophotometry studies. Moreover, the required blood volume is very small so the system can evaluate artificial blood or artificial red cells at very low cost. Thus, this system can reduce the time and cost of developing new pulse photometry techniques and other medical equipment.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2008; 2008:670-3. DOI:10.1109/IEMBS.2008.4649241
  • H Suzaki · S Takeda · N Kobayashi · H Kubota · T Aomi · T Nagaoka · K Iwasaki · M Umezu · A Uchiyama
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    ABSTRACT: Optical properties of living tissues have not been well established even today, and bioopticinstrumentations have to be based on empirical formulae. In order to examine optical properties of the tissue having pulsating blood perfusion, we investigated the relation between optical density (defined as O.D.) of whole blood and hematocrit by transmission spectrophotometry. We used Waseda mock circulatory system that simulates blood circulation in the tissue. It was found that with increasing light path length, O.D. per unit light path length due to scattering and absorption effect, tended to become constant in each hematocrit. For wavelengths of 660, 805 and 940 nm, the relations between O.D. of whole blood and hematocrit predicted by Twersky's equation, Loewinger's equation and photon diffusion equation fitted to the data obtained. Meanwhile, for 1300 nm, the relation predicted by Loewinger's equation gave the best fit to the data.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2005; 3:2626-9. DOI:10.1109/IEMBS.2005.1617008
  • Y Fujita · T Yamamoto · M Fuse · N Kobayashi · S Takeda · T Aoyagi
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    ABSTRACT: We evaluated the validity of a newly developed pulse dye densitometer for indigo carmine for measuring cardiac output and circulating blood volume. Measurements of cardiac output and circulating blood volume were performed with the indigo carmine densitometer during normovolaemia, hypovolaemia and hypervolaemia in nine mongrel dogs under general anaesthesia. The validity was evaluated by comparison of the values of cardiac output and circulating blood volume obtained by the thermodilution technique and the 51Cr-labelled red blood cell method, respectively. We also examined indigo carmine removal by continuous veno-venous haemofiltration after indigo carmine injection. There was good agreement between dye densitometer- and thermodilution-derived cardiac output (r = 0.885, P < 0.001). The bias and limits of agreement of these values were 0.09 and+/-1.07 L min(-1) (2 SD, n 22), respectively. The dye-densitometer-derived circulating blood volume was greater than that of the 51Cr-labelled red blood cell method, and both values showed weak agreement (r = 0.587, P < 0.027). The sieving coefficient of indigo carmine through continuous veno-venous haemofiltration was 0.34+/-0.06. These data indicate that indigo carmine densitometry is a reliable method for cardiac output determination, but it overestimates circulating blood volume, probably due to the transition of indigo carmine into the extravascular space in the systemic circulation.
    European Journal of Anaesthesiology 08/2004; 21(8):632-7. DOI:10.1017/S0265021504008087 · 3.01 Impact Factor