title: Development of a method for estimating oesophageal temperature by multi-locational temperature measurement inside the external auditory canal.
abstract: We aimed to develop a practical method to estimate oesophageal temperature by measuring multi-locational auditory canal temperatures. This method can be applied to prevent heatstroke by simultaneously and continuously monitoring the core temperatures of people working under hot environments. We asked 11 healthy male volunteers to exercise, generating 80 W for 45 min in a climatic chamber set at 24, 32 and 40 °C, at 50% relative humidity. We also exposed the participants to radiation at 32 °C. We continuously measured temperatures at the oesophagus, rectum and three different locations along the external auditory canal. We developed equations for estimating oesophageal temperatures from auditory canal temperatures and compared their fitness and errors. The rectal temperature increased or decreased faster than oesophageal temperature at the start or end of exercise in all conditions. Estimated temperature showed good similarity with oesophageal temperature, and the square of the correlation coefficient of the best fitting model reached 0.904. We observed intermediate values between rectal and oesophageal temperatures during the rest phase. Even under the condition with radiation, estimated oesophageal temperature demonstrated concordant movement with oesophageal temperature at around 0.1 °C overestimation. Our method measured temperatures at three different locations along the external auditory canal. We confirmed that the approach can credibly estimate the oesophageal temperature from 24 to 40 °C for people performing exercise in the same place in a windless environment.
authors.affiliation: Department of Health Policy and Management, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Nakada
authors.affiliation: Department of Health Policy and Management, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan. horie@med.uoeh-u.ac.jp.
authors.forename: Seichi
authors.identifier: http://orcid.org/0000-0002-8347-2630
authors.initials: S
authors.lastname: Horie
authors.affiliation: Department of Health Policy and Management, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan.
authors.forename: Shoko
authors.initials: S
authors.lastname: Kawanami
authors.affiliation: Department of Health Policy and Management, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan.
authors.forename: Jinro
authors.initials: J
authors.lastname: Inoue
authors.affiliation: Midori Electric Company, Chikuma, Nagano, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Iijima
authors.affiliation: Midori Electric Company, Chikuma, Nagano, Japan.
authors.forename: Kiyoharu
authors.initials: K
authors.lastname: Sato
authors.affiliation: Midori Anzen Company, Tokyo, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Abe
mesh_terms: D000328:Adult; D001831:Body Temperature; D004424:Ear Canal / Q000502:physiology*; D004947:Esophagus / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D006801:Humans; D006813:Humidity; D007259:Infrared Rays; D008297:Male; D008954:Models, Biological; D013696:Temperature; D055815:Young Adult
keywords: Body temperature changes; Heatstroke; Occupational health services; Occupational medicine; Physiologic monitoring