© 2009 Delmar, Cengage Learning Chapter 18 Medical Math

© 2009 Delmar, Cengage Learning

Chapter 18

Medical Math


Introduction

• Math skills are a requirement for working in a health care occupation

• Calculations are needed for– Correct medical dosages

– Recording height and weight

– Intake and output measurement of fluids

(continues)


Introduction(continued)

– Administrative tasks such as bookkeeping and billing

– Tests performed in the lab

– Mixing of cleaning fluids

• Health care workers must make every effort to achieve 100% accuracy


18:1 Basic Calculations

• It is necessary to be able to add, subtract, and divide whole numbers, decimals, fractions, and percentages

• Understanding of equivalents when using decimals, fractions, and percentages

• When taking professional exams for licensure or certification, calculators are sometimes not allowed


Whole Numbers

• Do not contain decimals or fractions

• Addition—adding numbers together to find the total amount

• Several uses in health care– Inventory records

– Statistical information on patients

• Example

(continues)


Whole Numbers(continued)

• Subtraction—taking a number away from a number to find the difference

• Several uses– Weight loss

– Pulse deficit calculation

• Example

(continues)



• Multiplication—same as addition or multiplying to find the quantity

• Several uses include– Payroll records (salary amount paid for number

of hours worked)

– Microscope power magnification

• Example

(continues)



• Division—finding how many times a number is contained in another number– Finding cost of one item

– Determining amount of diet nutrients

• Example


Decimals

• Decimals—are based on the number 10

• Represent the number of tenths, hundredths, thousandths, and so on

• Are added, subtracted, multiplied, and divided the same as whole numbers

• Always check the placement of the decimal point to avoid mistakes

• Examples (See Table 18-1 in text)


Fractions

• Fraction—a quantity less than a whole number expressed as a decimal

• Has a numerator (top number) and a denominator (bottom number)

• Some fractions need to be reduced to their lowest term

• See Table 18-2 in text

• Examples(continues)


Fractions(continued)

• Improper fractions—numerators are larger than denominators

• Converting fractions is used for addition and subtraction

• Multiplying fractions

• Dividing fractions—needs to be inverted (reciprocal) and then multiplied

• Examples


Percentages

• Percentages—whole or proportion of a whole (100%)

• See Figure 18-4 in text

• Advantage is to convert the percentage to a decimal before adding, subtracting, multiplying, and dividing

• Examples


Ratios

• Shows relationship between like values

or numbers

• Health care workers use ratios for strengths of solutions

• 50 percent strength solution is 1:2 ratio


Converting Decimals, Fractions, Percentages, and Ratios

• Decimals, fractions, and percentages represent parts of a whole

• There are specific methods of conversion from one to another



Rounding Numbers

• This requires changing them to the nearest ten, hundred, thousand, and so on

• Depends on degree of accuracy

• Refer to Table 18-4 in text

• Examples


Solving Problems with Proportions

• Proportion—equality between two ratios (“two is to six as three is to nine”)

• For converting from one unit to another when three in the proportion are identified

• Examples


18:2 Estimating

• Estimating—a reasonable approximate calculation of the answer

• Errors can occur with numbers in wrong order or decimal points misplaced

• Practice and thought is needed when learning to estimate answers and detecting incorrect answers

• Examples


18:3 Roman Numerals

• Numbers used today are known as Arabic numerals (1, 2, 3, and so on)

• In the health care field Roman numerals are used for specific reasons

• Examples



18:4 Angles

• Used in health care for– Injection of medications

– Description of joint movements

– Indication of bed positions

(continues)


Angles(continued)

• Angles are made when two plane surfaces meet along a line

• The distance between the plane and line of the angle is measured in degrees

• See Figure 18-6 in text

• Examples


18:5 Systems of Measurement

• Various systems of measurement used in health care

• Terminology in each system– Distance (length)

– Capacity (volume)

– Mass (weight)

• Each system has its own method of naming (nomenclature)


Household System

• Used in the United States


• With basic equivalents known then unknown measurements can be found by using proportions

• Examples


Metric System

• More accurate than the household system

• Metric units– Distance/length: meter (m)

– Capacity/volume: liter (l or L)

– Mass/weight: gram (g or gm)


• Metric system based on multiples of tens

• Examples


Apothecary System

• Oldest and used less than the metric or household systems

• Still used by some doctors

• Necessary for health care workers to be able to convert within the system


(continues)


Apothecary System(continued)

• Use of lowercase and uppercase Roman numerals sometimes used along with this system

• Example


Converting Systems of Measurement

• Health care workers need to be aware of equal values between units

• Not an exact science when converting

• The answer is considered to be approximately the same


• Examples


18:6 Temperature Conversion

• Use of the Fahrenheit (F) thermometer scale in the United States

• Centigrade (Celsius) or C is often used in health care

• Conversion charts and formulas (using fractions or decimals) are available

• See Tables 18-10 and 18-11 in text


18:7 Military Time

• Traditional system of correct time uses

A.M. and P.M. (12 hours)

• Errors can occur if time is misread

• Accuracy of time is critical in health care

• Military time is based on a 24-hour day

• Avoids any confusion


• Examples

Documents

© 2009 Delmar, Cengage Learning Chapter 18 Medical Math