CONVERSION AND CALCULATIONS OF HEALTHCARE MEASUREMENTS

METRIC UNITSMeasurements are used often in Healthcare.

The Clinical laboratory uses measurement in almost all aspects of its operation.

Ex. Solution Concentrations

Cell CountsDensity of Specimens

Volume of Solutions/BloodDilutions

TimeTemperatures

WHICH METHOD IS BEST TO CONVERT BETWEEN UNITS?

Converting between units can be done in different ways. Initially, students learn to convert units using the ladder method. This method is not appropriate for healthcare.

As conversions progress in difficulty, particularly between measurement systems it is best to use the dimensional analysis /proportional relationship method.

SCIENTISTS AND HEALTHCARE PROFESSIONALS WORK IN METRIC UNITS

Measurements made in the Healthcare Laboratory have a direct impact on the quality of patient care. It can be a matter of determining a diagnosis, follow the course of a disease and prescribing the correct treatment.The measurement must be reliable, accurate, standardized and precise. Measurements in healthcare can mean the differencebetween life and death.

4/20/01

0.5 versus 5

SYSTEMS OF MEASUREMENT

United States English System of Measurement, sometimes called the U.S.

customary system. Used in every day life in the U.S. for measurement.

English Units for Distance:Inch, feet, yard, mile, etc.

Example: How many inches are there in 12 feet?

12 inches (”) =1foot (’)12” * 12’ = 144”

ENGLISH SYSTEM OF MEASUREMENT

Other common Units in the English System

Pound

Cups

Pint

Miles

These units are not accurate enough for scientific measurement; hence the most accurat system the metric system is used.

METRIC SYSTEM

Used internationally by scientists and Healthcare

In most countries the metric system is used in everyday

The metric system is based on the power of 10, decimal system with a fundamental unit

Due to the decimal system very, very small quantities can be measured accurately and easily.

GROUPS OF TEN

The Metric system is based on Powers of Ten. Ten of one unit equals 1 of the next, and ten of those equals 1 of the next… and so on and so on.

BASE UNITS OF THE METRIC SYSTEMDifferent units are used to measure different things.Length – MetersMass – GramsVolume – LitersDensity – Mass/Volume

Also part of the Metric System:Temperature - Celsius

MEASUREMENTS OF LENGTH

Base Unit Meter

Type of Measure Length

Tool Ruler

MEASUREMENTS OF MASS

Base Unit Gram

Type of Measure Mass

Tool Scale

MEASUREMENTS OF VOLUME

Base Unit Liter

Type of Measure Volume

Tool Graduated Cylinder

Base Unit Degree Celsius

Type of Measure Temperature

Tool Thermometer

MEASUREMENT OF TEMPERATURE

TEMPERATURE IS NOT REPORTED IN METRIC OR SI UNITS

Three ScalesFahrenheit

boiling point 212° F freezing point 32 ° F

Used in the U.S. for cooking, body temperature and weatherCelsius

boiling point 100° C freezing point 0° C

Used for making most scientific temperature measurements. Most countries other than the US use the Celsius scale for everyday temp.

Kelvin The Kelvin scale is a scientific scale for the temperature

above absolute zero (0 K, -273.15 °C). The difference in scales is 273.15.

CONVERSION OF TEMPERATURE

CONVERSION OF TEMPERATURE

If someone says that the temperature will be 303 K today, how can you express that temperature in °C and °F?

Try to Solve

To convert from Kelvin to Celsius:

TC = TK - 273

To convert from Celsius to

Fahrenheit:TF = 9/5(TC) + 32

CONVERSION OF TEMPERATUREIf someone says that the temperature will be 303 K today, how can you express that temperature in °C and °F?To convert from Kelvin to Celsius:TC = TK - 273TC = 303 - 273 TC = 30°CTo convert from Celsius to Fahrenheit:TF = 9/5(TC) + 32TF = 9/5(30) + 32TF = 86°F

Temperature Conversion Answer30°C, 86°F

INTERNATIONAL SYSTEM OF UNITS

Standardize scientific measurements worldwide

In the U.S. SI units are mandated in all federal agencies

SI units are derived from the metric system are based on seven fundamental units.

http://physics.nist.gov/cuu/Units/units.html

AGAIN THE FUNDAMENTAL UNITS OF THE METRIC SYSTEM ARE…

Different units are used to measure different things.

Length – Meters

Mass – Grams

Volume – Liters

Density – Mass/Volume

Also part of the Metric System:

Temperature - Celsius

COMMON BASIC UNITS IN HEALTHCARE

Liter

Meter

Gram

In the laboratory it is more common to measure smaller units than the basic units.

METRIC SYSTEM USES POWER OF 10

Prefixes are added to the base unit (ex. liter,meter or gram) to indicate larger or smaller units.

mega- M million 1,000,000 106

kilo- k thousand 1,000 103 kilograms

deci- d tenth 1/10 = 0.1 10-1 dm3=litercenti- c hundredth 1/100 = 0.01 10-2 cm=centimeter

cc=cubic cmmilli- m thousandth 1/1000 = 0.001 10-3 mg=milligram

mL=millilitermicro- µ millionth 1/1,000,000

= 0.00000110-6 µg=microgram

nano- n billionth 1/1,000,000,000= 0.000000001

10-9 nm=nanometers

ExamplesMetric facts: 1 cubic centimeter = 1 milliliter (1 cc=1mL)Liter = 1 cubic decimeter = 1,000 cubic centimeters = 1,000 millilitersLower case “m” stands for meter or “milli”. Capital “L” for liter.

UNIT PREFIXES

Simply add a prefix to the unit to show the quantity, size or value in powers of tenUnits Larger than the base:deca = 10 xhecto = 100 xkilo = 1,000 xUnits Smaller than the base:deci = .1 xcenti = .01 xmilli = .001 x

WHAT TO DO TO SOLVE METRIC CONVERSIONS PROBLEMS?

Identify what you are asked.

Write down what is given or known.

Look for relationships between knowns and unknowns (use charts, equations).

Rearrange the equation to solve for the unknown.

Do the computations, cancel the units, check for reasonable answers.

STEPS OF DIMENSIONAL ANALYSIS

Start with what value is known, proceed to the unknown. Starting point = the number and unit provided by the

question Final destination = the units desired after converting

Draw the dimensional lines (count the “jumps”).

Insert the unit relationships.

Cancel the units.

Do the math, include units in answer.

DIMENSIONAL JUMPS BETWEEN PREFIXES

How many jumps between deci and giga 10-1 x 10 9 = 10 jumps (9-(-1) =10)

WRITE THE KNOWN, IDENTIFY THE UNKNOWN.

EX. How many km is 582 mm ?

582mm = ______km

DRAW THE # OF DIMENSIONAL “JUMPS”

EX. How many km is 582 mm ?

582 mm2 x_____ x_____x_____x_____x_____x_____

USING THE DIMENSIONAL JUMP METHOD

582 mm x_____ x_____x_____x_____x_____x___

CANCEL UNITS

582mm x x x x x x

mm

cm

cm

dm

dm

m

m

dkm

dkm

hm

hm

km

*Units leftover SHOULD be units ofUNKNOWN

INSERT RELATIONSHIPS (PREFIXES FROM THE KNOWN TO THE UNKNOWN)How many km is 582 mm ?

582 mm x_.1cm_ x_____x_____x_____x_____x_____

.1m

1 mm 1cm

.1dm

1 dm 1m

.1dkm

1dkm 1hm

.1hm .1km

DO THE MATH

582mm x x x x x x

mm

cm

cm

dm

dm

m

m

dkm

dkm

hm

hm

km

DO THE MATH

582mm x 10 -6 = .000582 km

CHART METHODCONVERT 5234 MILLIMETERS TO METERS

5234 millimeters = meters

Starting amount End Amount

milli

0.001

5234 millimeters 5234 meters1000

equal

CONVERT 21 MG PER LITER (21 G/L) TO GRAMS PER 100 CC

21 mgLiter

= g 100cc

Starting amount End Amount

0.001

milli

equal equal

1L1000cc

0.10.1

equal

0.00021

CONVERSION OF METRIC UNITS TO METRIC UNITS

The ratio and proportion procedures is probably the most useful way to convert one unit of measure to another

Ex.

How many milligrams equal 0.025g?The unknown ratio is 0.025g to “x” mg.Make a ratio:

0.025g/x mg = 1g/1,000mgx= 0.025 X 1,000 x = 25 mg

Hence 25mg = 0.025g