Core temperature is 98.6°F (37.0 °C)
(1) defined as temperature in right atrium of the heart
(2) lower esophageal temperature can be used as a measure of core body temperature
(3) temperature of freshly voided urine approximates core body temperature
Rectal temperature:
(1) approximates core temperature
Oral temperature:
(1) 0.3-0.6 °C (0.5-1.1°F, mean 0.8 °F) below rectal temperature
(2) may be falsely low with rapid respirations, mouth breathing or cold drinks
(3) may be falsely elevated after ingesting warm drinks
Axillary temperature:
(1) may be 1°C (1.8°F) lower than core temperature
(2) affected by degree of cutaneous vasoconstriction
Based on the above information:
(1) oral temperature in °F = (axillary temperature) + (1°F +/- 0.3 °F)
(2) oral temperature in °F = (rectal temperature) - (0.8°F +/- 0.3°)
(3) rectal temperature in °F = (axillary temperature) + 1.8°F
(4) rectal temperature in °F = (oral temperature) + (0.8°F +/- 0.3°)
(5) axillary temperature in °F = (oral temperature) - (1°F +/- 0.3 °F)
(6) axillary temperature in °F = (rectal temperature) - 1.8°F
