Thermometer Health Article

Definition

A thermometer is a device used to monitor temperature.

Purpose

A thermometer is used to establish a baseline on the admission of a patient to a health care facility, to detect any abnormalities from the normal state, and to establish if current medication is having the desired effect.

Temperature is recorded to check for pyrexia or monitor the degree of hypothermia present in the body. The body's normal temperature is 98.6°F (37°C). A fever is a temperature of 101°F or higher in an infant younger than three months or above 102°F for older children and adults. Hypothermia is recognized as a temperature below 96°F (35.5°C).

Description

A thermometer can be mercury, liquid-in-glass, electronic with digital display, infrared or tympanic, or disposable dot-matrix. It can be used in a clinical or emergency setting or at home.

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 Fahrenheit, Centigrade or both. Mercury is held in a reservoir bulb at one end that rises 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 to 105°F, (35°C to 42°C) and can be used orally, axilliary (under the arm), or rectally. They have temperature sensors inside round-tipped probes and can be covered with disposable guards to prevent infection passing from one patient to another. The sensor is connected to the container housing the central processing unit, and the information gathered by the sensor is then shown on the display screen. Some models have other features such as memory recall of the last recording and a large display screen for easy reading. The thermometer probe is placed under the arm, tongue, or placed in the rectum and held in place for a few seconds, depending on the model used. The device will beep when the peak temperature is reached. The time required for obtaining the reading is between a few seconds to thirty seconds.

A tympanic thermometer has a round-tipped probe containing the sensor that can be covered with disposable guards to prevent infection from one patient to another. It is placed in the ear canal for one second 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 that have chemicals impregnated in dots on the surface. They are sticky on one side to adhere to the skin and prevent slippage and are worn under the armpit. The dots change color at different times as the chemicals respond to the body heat. The temperature is readable after two to three minutes, depending on the manufacturer's guidelines. Some products are disposable, reusable, or can be used continuously for up to 48 hours. These devices are useful for children, and the temperature can be recorded even while the child is asleep.

Operation

The patient should be sitting or lying comfortably to ensure that the readings are taken in similar positions each time and that there is little excitement to affect the results.

The manufacturer's guidelines should be followed when taking a temperature with a digital, tympanic, or disposable thermometer. Dot-matrix thermometers are placed next to the skin and usually held in place by a sticky strip. With the tympanic thermometer, caregivers should ensure that the probe is properly inserted into the ear in order to allow an optimal reading. The reading will be less accurate if the sensor cannot accurately see the tympanic membrane or if the view is obscured by wax and debris in the ear canal.

A mercury thermometer can be used to monitor a temperature by three methods:

• Axilliary.
• Orally or sub-lingually. This method is never used with infants.
• Rectally. This method is used with infants. The tip of the thermometer is usually blue-tipped to distinguish it from the silver tip of an oral/axilliary thermometer.