Additional Conversions Useful in the Health Care Setting

CHAPTER 9


Additional Conversions Useful in the Health Care Setting



Objectives


After reviewing this chapter, you should be able to:


1. Convert between Celsius and Fahrenheit temperature


2. Convert between units of length: inches, centimeters, and millimeters


3. Convert between units of weight: pounds and kilograms, pounds and ounces to kilograms


4. Convert between traditional and military (international) time



CONVERTING BETWEEN CELSIUS AND FAHRENHEIT


Many health care facilities use electronic digital temperature-taking devices that instantly convert between the two scales; however, such devices do not eliminate the need for the nurse to understand the difference between Celsius and Fahrenheit. In addition, it may be necessary for the nurse to explain to clients or families how to convert from one to the other.


Another factor is the recognition that all persons involved in client care do not have a “universal” measurement for temperature; therefore Fahrenheit or Celsius may be used. Let’s look first at some general information that will help you understand the formulas used.



Differentiating Between Celsius and Fahrenheit


To differentiate which scale is being used (Fahrenheit or Celsius), the temperature reading is followed by an F or C. F indicates Fahrenheit, and C indicates Celsius. (Note: Celsius was formerly known as centigrade.)




Examples:

98° F


36° C


The freezing point of water on the Fahrenheit scale is 32° F, and the boiling point is 212° F. The freezing point of water on the Celsius scale is 0° C, and the boiling point is 100° C.


The difference between the freezing and boiling points on the Fahrenheit scale is 180°, whereas the difference between these points on the Celsius scale is 100°.


The differences between Fahrenheit and Celsius in relation to the freezing and boiling points led to the development of appropriate conversion formulas. Figure 9-1 shows two thermometers reflecting the relationship of pertinent values between the two scales. Figure 9-2 shows medically important Celsius and Fahrenheit temperature ranges.


image
Figure 9-1 Celsius and Fahrenheit temperature scales. (From Clayton BD, Stock YN: Basic pharmacology for nurses, ed. 14, St. Louis, 2007, Mosby.) Note: Glass thermometers pictured here are for demonstration purposes only. Electronic digital temperature devices are more commonly used in health care settings.

image
Figure 9-2 Ranges of normal temperature values and physiological consequences of abnormal body temperature. (From Potter PA, Perry AG: Fundamentals of nursing, ed. 7, St. Louis, 2009, Mosby.)

The 32° difference between the freezing point on the scales is used for converting temperature from one scale to the other. There is a 180° difference between the boiling and freezing points on the Fahrenheit thermometer and 100° between the boiling and freezing points on the Celsius scale. These differences can be set as a ratio, 180:100. Therefore consider the following:


180:100=180100=95


image

The fraction 95image expressed as a decimal is 1.8; therefore you will see this constant used in temperature conversions.



FORMULAS FOR CONVERTING BETWEEN FAHRENHEIT AND CELSIUS SCALES



RULE


To convert from Celsius to Fahrenheit, multiply by 1.8 and add 32.



°F=1.8(° C)+32or°F=95(° C)+32


image



NOTE


Your preference for one of these formulas is based on whether you find it easier to work with decimals or fractions.







Example:

Convert 68° F to ° C.


° C=68–321.8° C=(68–32)÷95° C=361.8or° C=36÷95° C=(36) × 59° C=20°° C=20°


image



image Practice Problems


Convert the following temperatures as indicated (round your answer to tenths).




Change the given temperatures in the following statements to their corresponding equivalents in ° C or ° F.




Answers on p. 607



In addition to temperature conversions, other measures that may be encountered in the health care setting relate to linear measurement. As with temperature conversion, even though there are devices that instantly convert these measures, nurses need to understand the process. For the purpose of this chapter, we will focus on millimeters (mm) and centimeters (cm).



METRIC MEASURES RELATING TO LENGTH


In health care settings metric measures relating to length are used. Diameter of the pupil of the eye may be described in millimeters; the normal diameter of pupils is 3 to 7 mm. Charts may show pupillary size in millimeters. Accommodation of pupils is tested by asking a client to gaze at a distant object (e.g., a far wall) and then at a test object (e.g., a finger or pencil) held by the examiner approximately 10 cm (4 in) from the bridge of the client’s nose.


A baby’s head and chest circumference are expressed in centimeters. Gauze for dressings is available in different size squares measured in centimeters.








Example 3:

An infant’s head circumference is 35.5 cm. How many millimeters is this?



NOTE


Any of the methods presented in previous chapters may be used for conversion. Remember, however, that decimal movement is limited to conversions from one metric measure to another, and the number of places the decimal is moved is based on the conversion factor. If necessary, review previous chapters relating to converting.

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Feb 11, 2017 | Posted by in PHARMACY | Comments Off on Additional Conversions Useful in the Health Care Setting

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