Vital Signs: Assessing Temperature

Temperature Measurement

• Core body temperature is approximately 37°C (98.6°F) and fluctuates around 1°C over the course of the day.
• Body temperature can be measured from several different areas of the body.
• Women have a wider range of normal temperature than men.

Advantages and Disadvantages of Four Sites for Body Temperature Measurement

Axillary

• Advantages: safe and non-invasive
• Disadvantages: thermometer must be left in place for a long time to obtain an accurate measurement

Tympanic Membrane

• Advantages: readily accessible; reflects the core temperature
• Disadvantages: can be uncomfortable; involves risk of injuring the membrane if the probe is inserted too far; repeated measurements may vary; presence of cerumen can affect the reading
• Contraindications: presence of earache, significant ear drainage, scarred tympanic membrane, sleeping with the head turned on one side

Oral

• Advantages: accessible and convenient
• Disadvantages: glass thermometers can break if bitten; inaccurate if client has just ingested hot or cold food or fluid or smoked; could injure the mouth following oral surgery
• Contraindications: infants and very young children, patients with oral surgery, unconscious or irrational patients, seizure-prone patients, mouth breathers

Rectal

• No specific advantages or disadvantages mentioned

Temporal and No-Touch

• No specific advantages or disadvantages mentioned

Normal Ranges of Temperature

• Oral: 95.9-99.5°F (3-10 years), 97.6-99.6°F (11-65 years), 96.4-98.5°F (65 years and older)
• Tympanic Membrane: 97.5-100.4°F (0-2 years), 97-100°F (3-10 years), 96.6-99.7°F (11-65 years), 96.4-99.5°F (65 years and older)
• Rectal: 97.9-100.4°F (0-2 years), 97.9-100.4°F (3-10 years), 98.6-100.6°F (11-65 years), 97.1-99.2°F (65 years and older)
• Axillary: 94.5-99.1°F (0-2 years), 96.6-98.0°F (3-10 years), 95.3-98.4°F (11-65 years), 96-97.4°F (65 years and older)
• Temporal and No-Touch: 97.9-110.7°F (0-2 years), 97.9-100.3°F (3-10 years), 97.9-100.1°F (11-65 years), 97.9-100.1°F (65 years and older)
• Core: 97.5-100.0°F (0-2 years), 97.5-100°F (3-10 years), 98.2-100.2°F (11-65 years), 96.8-98.8°F (65 years and older)

Conversion of Celsius to Fahrenheit and Vice Versa

• Formula to convert Fahrenheit to Celsius: C = (F – 32) × 5/9
• Formula to convert Celsius to Fahrenheit: F = (C × 9/5) + 32

Definition of Terms

• Body temperature: the balance between heat produced and heat lost by the body
• Fever (Pyrexia): elevated body temperature
• Hyperpyrexia: body temperature above 41°C
• Afebrile: normal body temperature, without fever
• Hypothermia: abnormally low body temperature, below 35°C rectally

Types of Fever

• Intermittent: temperature alternates at regular intervals between periods of fever and periods of normal or subnormal temperatures
• Remittent: wide temperature fluctuation (more than 2°C) occurs over the 24-hour period, all of which is above normal
• Relapsing: short febrile periods of a few days are interspersed with periods of 1 or 2 days of normal temperature
• Constant: body temperature fluctuates minimally but always remains above normal

Process of Heat Loss

• Radiation: surface to surface by waves
• Conduction: contact between 2 surfaces
• Convection: movement by air currents or fluid
• Evaporation: water to steam
• Elimination: urination, defecation

Factors that Might Alter Core Body Temperature

• Infection
• Metabolism
• Age
• Temperature of the environment
• Diurnal variations (circadian rhythms)
• Malignancy
• Trauma such as surgery or crush injuries
• Drug reactions
• Immune disorders
• Amount of exercise
• Hormones