This article is about some different types of clinical thermometers found in clinical areas. It should be noted that due to the toxic effects of mercury fumes, mercury thermometers are quickly being replaced by electronic ones. Finally, it must be noted that the axillary temperature is about 0.5 of a degree lower than the tympanic temperature.

Clinical Thermometers.

A clinical thermometer is a specialized instrument to measure the temperature of a patient. Clinical thermometers contain mercury or alcohol which expands when heated to give an accurate temperature of the patient within a specified range. A more specialized thermometer should be used when taking the temperature of an individual who is hypothermic.

Until very recently mercury and/or alcohol thermometers were the most common. These were easy to make, cheap, accurate and were portable. Further they were easy to use. However, over the last two to three decade society has become more aware of the toxic side effects of mercury. Mercury fumes which can be inhaled by staff and patients have toxic effects to those exposed. So mercury thermometers are being replaced by electronic thermometers.

Look the pictures of the two mercury thermometers. One is red and the other is blue. In most clinical situations both of these are present. Can you figure out why two thermometers of different colors are present beside each patient?

Industrial thermometers are generally graduated from about -5 to 105 degrees. Look at the clinical thermometers. Look at the lowest possible temperature and the highest possible temperature on these two thermometers. What are the lowest and highest temperatures which these thermometers can record?

Why do you need a more specialized thermometer to record the temperature of a patient who is hypothermic? Where are you likely to get a hypothermic patient in Darwin or in Toronto?

A Mercury Thermometer. Why is it Blue?

Answer: In most wards blue covered or blue labeled thermometers are for taking the temperature from the axilla of the patient.

A Mercury Thermometer. Why is it Red?

Answer: In most clinical areas red thermometers are for taking rectal temperatures.

Electronic thermometers are relatively cheap and easy to use. They do not carry the risks associated with mercury thermometers. However, there are very expensive electronic thermometers too. The “Industrial” electronic thermometer shown below is very expansive and can be damaged if it falls to the ground. Further, the protective ear pieces which must be changed whenever taking the patient's are expensive too.

Why must the ear pieces be changed when taking the temperature? There are two reasons for this. What are the two reasons?

Answers: Changing the ear pieces resets the thermometer to take a new temperature.

b. Changing the ear piece prevents the spread of infections.

Where are the ear pieces located on the clinical thermometer shown in figure 4?

Why are they disposable?

Answers: The ear pieces are located below the handset and are visible in this picture.

They are disposable to reduce the spread of infection.

What is the most significant difference the user will need to be aware of when using these two thermometers?

Answer: The thermometer is figure 3 will be used to take the temperature of the patient from between two folds of skin e.g. axilla. The thermometer in figure 4 will be used to take the temperature from the patient's tympanic membrane. There is a significant difference in axillary and tympanic temperatures.