Conversion and Calculations of Healthcare Measurements

Solution Concentrations Volume of Solutions/Blood Metric Units Measurements are used often in Healthcare. The Clinical laboratory uses measurement in almost all aspects of its operation. Ex. Solution Concentrations Cell Counts Density of Specimens Volume of Solutions/Blood Dilutions Time Temperatures

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 difference between life and death. Reinforce the importance of precision and accuracy of measurement in Health Care.

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. Have students come up with a mnemonic to help them remember the powers of 10 Example: King Henry Died Basically Drinking Chocolate (Kilo, Hecta, Deca, Basic Unit, Deci, Centi, Milli, Micro, Nano).

Base Units of the Metric System 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 Differentiate between the English and Metric Measurement in Healthcare. Emphasize the base units for length (m), mass (g), volume (L), density (g/ml). Temperature ©, and the tools to conduct each measurement. It may be a good idea to demonstrate the different measurements for the class.

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

Measurement of Temperature Base Unit Degree Celsius Type of Measure Temperature Tool Thermometer

Temperature is not reported in metric or SI units Three Scales Fahrenheit boiling point 212° F freezing point 32 ° F Used in the U.S. for cooking, body temperature and weather Celsius 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 Temperature If 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 - 273 TC = 303 - 273 TC = 30°C To convert from Celsius to Fahrenheit: TF = 9/5(TC) + 32 TF = 9/5(30) + 32 TF = 86°F Temperature Conversion Answer 30°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.

cm=centimeter cc=cubic cm milli- m thousandth 1/1000 = 0.001 10-3 mega- M million 1,000,000 106 kilo- k thousand 1,000 103 kilograms deci- d tenth 1/10 = 0.1 10-1 dm3=liter centi- c hundredth 1/100 = 0.01 10-2 cm=centimeter cc=cubic cm milli- m thousandth 1/1000 = 0.001 10-3 mg=milligram mL=milliliter micro- µ millionth 1/1,000,000 = 0.000001 10-6 µg=microgram nano- n billionth 1/1,000,000,000 = 0.000000001 10-9 nm=nanometers Examples Metric facts: 1 cubic centimeter = 1 milliliter (1 cc=1mL) Liter = 1 cubic decimeter = 1,000 cubic centimeters = 1,000 milliliters Lower 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 ten Units Larger than the base: deca = 10 x hecto = 100 x kilo = 1,000 x Units Smaller than the base: deci = .1 x centi = .01 x milli = .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) For the next few slides instructs students to identify the known and unknown and set up a proportional relationship, using both the chart and dimensional jump methods. Demonstrate both methods to the students.

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___

*Units leftover SHOULD be units of Cancel Units 582mm x mm cm dm m dkm hm km *Units leftover SHOULD be units of UNKNOWN

Insert Relationships (Prefixes from the known to the unknown) How many km is 582 mm ? 582 mm x_.1cm_ x_____x_____x_____x_____x_____ .1dm .1m .1dkm .1hm .1km 1 dm 1 mm 1cm 1m 1dkm 1hm

Do the Math 582mm x mm cm dm m dkm hm km

Do the Math 582mm x 10 -6 = .000582 km

Chart Method Convert 5234 millimeters to meters Starting amount equal End Amount 5234 millimeters 0.001 = meters milli 5234 millimeters 5234 meters 1000

Convert 21 mg per liter (21 g/L) to grams per 100 cc Starting amount equal equal equal End Amount 21 mg Liter 0.001 milli 1L 1000cc 0.1 0.1 = g 100cc 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/1,000mg x= 0.025 X 1,000 x = 25 mg Hence 25mg = 0.025g