Vol.1 No.1 2008

52/76

Research paper : Improving the reliability of temperature measurements taken with clinical infrared ear thermometers (J. Ishii)−48−Synthesiology - English edition Vol.1 No.1 (2008) thermometer that enabled “short measurement time” and “non-contact measurement”[1].In Japan, ear thermometers were introduced as instrument for medical specialists in the beginning of the 1990s. In 1996, it was formally approved as a medical device for general use, and became commercially available. The number of production and sales of ear thermometers in the Japanese market increased rapidly, and in a few years, reached around one million a year. The reasons for this rapid expansion were the fact that new ear thermometer satisfied user demands, and that the manufacturers had high hopes for this new innovative product that appeared in clinical thermometer market that reached maturity since the development of clinical electronic thermometer about a quarter of a century ago[2].On the other hand, with rapid diffusion of ear thermometers, questions and claims against the reliability of temperature readings of ear thermometers were made by users and consumer organizations, and drew attention of mass media such as newspapers and magazines. Therefore, as the national metrology institute of Japan, AIST started a research project to improve measurement accuracy of ear thermometers. After adjustments with manufacturers, users, and administrative bodies, the traceability system was established by 2002, and technological and social infrastructures were laid to maintain accuracy of temperature readings of ear thermometer.Also, the standard facility for calibration of ear thermometer which resulted from this research was provided to national standard institutions of Asian countries when severe acute respiratory syndrome (SARS) epidemic occurred in Asia in 2003, and helped to prevent the spread of infection[3].2 Public-private cooperation for problem solutionCurrently, mercury-in-glass and clinical electronic thermometers are designated “specified measuring instruments” under the Measurement Law administered by the Ministry of Economy, Trade and Industry. Instrumental error test (verification test) is conducted for all thermometers along with pattern approval test under government control. In contrast, testing and inspection according to technical guidelines of respective companies are conducted under responsibility of the thermometer manufacturers, for maintaining the reliability of temperature readings for newly developed and marketed ear thermometers.Ear thermometer attracted attention for its usability, and its use spread immediately after it became commercially available. On the other hand, complaints from users increased concerning its performance and reliability including differences in measurement principle and usage compared to conventional clinical thermometers. In 1998, the National Consumer Affairs Center of Japan, a public institution that conducts surveillance study from standpoint of consumer protection, reported “Attention! Ear Thermometers Tend to Measure High”,[4] and subsequently newspapers and magazines wrote that “the temperature readings show large variation” or “measurement is higher than actual temperature”.[5]In such a situation, “Survey and Research Committee for New Clinical Thermometer” was established in 1998 with members from the government (former Ministry of International Trade and Industry; former Ministry of Health and Welfare), medical professions, consumer organizations, clinical thermometer manufacturers, AIST (formerly National Research Laboratory of Metrology, Agency of Industrial Science and Technology). The committee conducted questionnaire survey to manufacturers and retailers of clinical thermometers, medical institutions, and consumers, to study the situation in Japan. According to this survey, while manufacture and sales of ear thermometer reached nearly 1 million per year, it became clear that neither medical specialists nor consumers had sufficient understanding of performance, measurement principle, usage, or reliability of ear thermometers[2].With cooperation of the committee members, AIST checked the temperature readings of ear thermometers in the market using an existing simple blackbody furnace, and found that some types of thermometers presented bias and large variations of 0.5 °C or more in temperature readings.Through this survey, two points were highlighted as technical issues arising from rapid market expansion of new ear thermometers:(1) Provision of sufficient information to users about measurement principle and proper usage(2) Establishment of technical standard, and traceability system for calibration and conformity assessment of ear thermometerOf the above two points, (1) was an issue mainly for manufacturers, retailers, and industry, while immediate effort by the government centering on AIST was strongly in demand for (2).The committee also conducted survey for the status of standardization,measurement standard and traceabilityTerm 4 for ear thermometers. Work on ear thermometer was done primarily in the United States, which was first in the world to market the product, and Germany, where it diffused widely after acquiring the technology from the U.S. In the United States, industrial

※このページを正しく表示するにはFlashPlayer9以上が必要です