Thermometer Health Article

Definition

A thermometer is a device used to measure temperature.

Purpose

A thermometer is used in health care to measure and monitor body temperature. In an office, hospital or other health care facility, it allows a caregiver to record a baseline temperature when a patient is admitted. Repeated measurements of temperature are useful to detect deviations from normal levels. Repeated measurements are also useful in monitoring the effectiveness of current medications or other treatments.

The patient's temperature is recorded to check for pyrexia or monitor the degree of hypothermia present in the body.

Demographics

All health care professionals use thermometers. All health care facilities have thermometers. Most homes also have thermometers.

Description

A thermometer can use any of several methods to register temperature. These include mercury; liquid-in-glass; electronic with digital display; infrared or tympanic; and disposable dot matrix. A thermometer can be used in a clinical or emergency setting or at home. Thermometers can record body temperatures in the mouth (oral), armpit (axillary), eardrum (tympanic membrane), or anus (rectal).

A mercury thermometer consists of a narrow glass stem approximately 5 in (12.7 cm) in length with markings along one or both sides indicating the temperature scale in degrees Fahrenheit, Centigrade or both. Liquid mercury is held in a reservoir bulb at one end and rises through a capillary tube when the glass chamber is placed in contact with the body. Mercury thermometers are not used in modern clinical settings.

Electronic thermometers can record a wide range of temperatures between 94°F and 105°F, (35°C and 42°C) and can record oral, axillary, or rectal temperatures. They have temperature sensors inside round-tipped probes that can be covered with disposable guards to prevent the spread of infection. The sensor is connected to a container housing the central processing unit. The information gathered by the sensor is then shown on a display screen. Some electronic models have such other features as memory recall of the last recording or a large display screen for easy reading. To use an electronic thermometer, the caregiver places the probe under the patient's arm or tongue, or in the patient's rectum. The probe is left in place for a period of time that depends on the model used. The device will beep when the peak temperature is reached. The time required to obtain a reading varies from 3–30 seconds.

A tympanic thermometer has a round-tipped probe containing a sensor that can be covered with a disposable guard to protect against the spread of ear infections. It is placed in the ear canal for 1 sec while an infrared sensor records the body heat radiated by the eardrum. The reading then appears on the unit's screen.

Digital and tympanic thermometers should be used in accordance with the manufacturer's guidelines.

Disposable thermometers are plastic strips with dots on the surface that have been impregnated with temperature-sensitive chemicals. The strips are sticky on one side to adhere to the skin under the armpit and prevent slippage. The dots change color at different temperatures as the chemicals in them respond to body heat. The temperature is readable after two to three minutes, depending on the instrument's guidelines. These products vary in length of use; they may be disposable, reusable, or used continuously for up to 48 hours. Disposable thermometers are useful for children, as they can record temperatures while children are asleep.