title: A comparison of the temperature difference according to the placement of a nasopharyngeal temperature probe.
abstract: BACKGROUND
  The purpose of this study was to compare temperatures measured at three different sites where a nasopharyngeal temperature probe is commonly placed.
  
  
  METHODS
  Eighty elective abdominal surgical patients were enrolled. After anesthesia induction, four temperature probes were placed at the nasal cavity, upper portion of the nasopharynx, oropharynx, and the esophagus. The placement of the nasopharyngeal temperature probes was evaluated using a flexible nasendoscope, and the depth from the nares was measured. The four temperatures were simultaneously recorded at 10-minute intervals for 60 minutes.
  
  
  RESULTS
  The average depths of the probes that were placed in the nasal cavity, upper nasopharynx, and the oropharynx were respectively 5.7 ± 0.9 cm, 9.9 ± 0.7 cm, and 13.6 ± 1.7 cm from the nares. In the baseline temperatures, the temperature differences were significantly greater in the nasal cavity 0.32 (95% CI; 0.27-0.37)℃ than in the nasopharynx 0.02 (0.01-0.04)℃, and oropharynx 0.02 (-0.01 to 0.05)℃ compared with the esophagus (P < 0.001). These differences were maintained for 60 minutes. Twenty patients showed a 0.5℃ or greater temperature difference between the nasal cavity and the esophagus, but no patient showed such a difference at the nasopharynx and oropharynx.
  
  
  CONCLUSIONS
  During general anesthesia, the temperatures measured at the upper nasopharynx and the oropharynx, but not the nasal cavity, reflected the core temperature. Therefore, the authors recommend that a probe should be placed at the nasopharynx (≈ 10 cm) or oropharynx (≈ 14 cm) with mucosal attachment for accurate core temperature measurement.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Chonbuk National University Medical School and Hospital, Jeonju, Korea.
authors.forename: Hyungsun
authors.initials: H
authors.lastname: Lim
authors.affiliation: Department of Anesthesiology and Pain Medicine, Chonbuk National University Medical School and Hospital, Jeonju, Korea.
authors.forename: Boram
authors.initials: B
authors.lastname: Kim
authors.affiliation: Department of Anesthesiology and Pain Medicine, Chonbuk National University Medical School and Hospital, Jeonju, Korea.
authors.forename: Dong-Chan
authors.initials: DC
authors.lastname: Kim
authors.affiliation: Department of Anesthesiology and Pain Medicine, Chonbuk National University Medical School and Hospital, Jeonju, Korea.
authors.forename: Sang-Kyi
authors.initials: SK
authors.lastname: Lee
authors.affiliation: Department of Anesthesiology and Pain Medicine, Chonbuk National University Medical School and Hospital, Jeonju, Korea.
authors.forename: Seonghoon
authors.identifier: 0000-0003-2742-9985
authors.initials: S
authors.lastname: Ko
keywords: Body temperature; Esophagus; Nasopharynx; Thermometers