OBJECTIVES
• At the end of this module, the student will be able to… Identify and compare the systems of
measurement used in the clinical setting. Identify the standard prefixes used in the metric
system State the metric units of length, mass, volume,
time, and temperature. Distinguish between the metric units for liquid
(mL) and solid volume (cc) measurements.
Measurement systems
• Method of quantifying matter Solids, liquids & gases
• Quantities include: Length Area Weight Volume Pressure Temperature Time
• Systems used in medicine:A. ConventionalB. MetricC. Standard International
Conventional Systems
• Also known as: British English U.S Customary (FPS) foot, pound, second(FPS) foot, pound, second
• Commonly used in U.S.
FPS
Examples of length & area
12 inches = 1 foot
3 feet (36 inches) = 1 yard
220 yards = 1 furlong
8 furlongs = 1 mile
1,760 yards = 1 mile
5,280 feet = 1 mile
1 sq. foot (foot2) = 122 sq. inches
1 sq. yard (yard2) = 9 sq. feet
43,560 sq. feet = 1 acre
1 sq. mile (mile2) = 640 acres
Examples of liquid measure
1 teaspoon (tsp) = 1/3 tablespoon
2 tablespoon (tbsp) = 1 fluid ounce
1 fluid ounce (oz) = 1/8 cup
2 fluid ounces = 1/4 cup
2 2/3 fluid ounces = 1/3 cup
4 fluid ounces = 1/2 cup
5 1/3 fluid ounces = 2/3 cup
6 fluid ounces = 3/4 cup
8 fluid ounces = 1 cup
2 cups (c) = 1 pint
2 liquid pints (pt) = 1 liquid quart (qt)
4 liquid pints = 1 gallon (gal)
Standard International (SI)
• Simplified modification of metric system.
• Worldwide effort started in 1960s to standardize to this system.
• Also known as: (MKS) meter, kilogram, second
MKS
Comparison
Conventional Units Standard International Units
Length inch or foot meter
Volume Fluid ounce
Cubic Foot (ft3)
Liter
Area in2 or ft2 m2
Metric System
• Developed in Europe.
• Has all units based on multiples of 10.
• Also known as: (CGS) centimeter, gram, second
CGS
Measurements in Respiratory Therapy• Length
Meter (m)
• Volume Liter (L)
• Mass Gram (g)
• Time Seconds (sec)
• Temperature Centigrade (Celsius), Kelvin, Fahrenheit
• Pressure Centimeters of Water (cm H2O), Pounds per square
inch (psi), Millimeters of mercury (mm Hg), Torr, Pascal (Pa), and Atmospheres (atm)
• Force Dynes
Conversion
• Conversion within the metric system is easy Everything based on multiples of ten.
• Conversion from one system to the other: MustMust know the conversion factors.
Conversion
• Conversion within these systems or from one system to the other: You Must know how to do metric conversions. I will provide the S.I. and conventional factors on
an exam or quiz.• There are too many to memorize.
• Gimli Glider & Mars Climate Orbiter
Basic (fundamental) Units
• Basic unit has value of one. (1x100 = 1) One Liter
• Smaller - milliliter
• Larger - kiloliter
One Gram• Smaller – microgram
• Larger - hectogram
One Meter• Smaller - decimeter
• Larger - Megameter Smaller
Larger
Opposite of the number line
Basic or Fundamental Unit
Liter
Gram
Meter
105 104 103 102 101 100 10-1 10-2 10-3 10-4 10-5
|-------|-------|-------|-------|-------|-------|-------|-------|------|-------|
kilo hecto deca deci centi milli
x1000 x100 x10
(k) (h) (da) (d) (c) (m)
LARGER SMALLER
Metric Chart
10
1
100
1
1000
1
Greek Prefixes - Units to the left of the basic unit and larger.• BASIC UNIT = One Liter, Gram or Meter
• 10 1 deca (da) 10 x larger 10
• 10 2 hecto (h) 100 x larger 100
• 10 3 kilo (k) 1000 x larger 1000
• 10 4
• 10 5
• 10 6 Mega (M) 1,000,000x 1,000,000
• 10 7
• 10 8
• 10 9 Giga (G) 1,000,000,000x 1,000,000,000
Latin Prefixes Units to the right of the basic unit and smaller.
• BASIC UNIT = One Liter, Gram or Meter
• 10 -1 deci (d); 10 x smaller; 1/10; x 0.1
• 10 -2 centi (c); 100 x smaller; 1/100; x 0.01
• 10 -3 milli (m); 1000 x smaller; 1/1,000; x 0.001
• 10 -4
• 10 -5
• 10 -6 micro () or (mc); 1,000,000 x smaller; 1/1,000,000; x 0.000001
• 10 -7
• 10 -8
• 10 -9 nano (n); 1,000,000,000 x smaller; 1/1,000,000,000; x 0.000000001
• 10-10 Angstrom (Å); 10,000,000,000 x smaller; 1/10,000,000,000; x 0.0000000001
Scientific Notation
• A method of expressing the value of a very small or very large number.
• Scientific Notation: (base exponent)
Base is the number to be multiplied by itself (usually 10).
Exponent is the number of times it is multiplied.
• 103 = 10 x 10 x 10 = 1,000
Scientific Notation
Example:
• A kilometer is 1,000 times larger than a meter
• Count the zeros (that equals exponent)
• 103
• 10x10x10 times larger
Scientific Notation
Example:• Angstrom (Å) is 10 billion times smaller than a meter
(m)• That is…10,000,000,000 times smaller• Count the zeros to determine exponent
or or
• Can also be written as 0.0000000001• 10x10x10x10x10x10x10x10x10x10 times smaller
1010
100000000010
1
,,,1010
Numbers and Exponents100= 1 a x 100 = a
101= 10 a x 101 = a x 10
102= 100 a x 102 = a x 100
103= 1000 a x 103 = a x 1000
106= 1,000,000 a x 106 = a x 1,000,000
109= 1,000,000,000 a x 109 = a x 1,000,000,000
10-1 = 0.1 a x 10-1 = a x 0.1
10-2 = 0.01 a x 10-2 = a x 0.01
10-3 = 0.001 a x 10-3 = a x 0.001
10-6 = 0.000001 a x 10-6 = a x 0.000001
10-9 = 0.000000001 a x 10-9 = a x 0.000000001
Numbers and Exponents
Positive exponent = # of zeros
5 x 100 = 5
5 x 101 = 50
5 x 102 = 500
5 x 103 = 5000
5 x 106 = 5,000,000
5 x 109 = 5,000,000,000
Negative exponent = # of decimal places
5 x 10-1 = 0.5
5 x 10-2 = 0.05
5 x 10-3 = 0.005
5 x 10-6 = 0.000005
5 x 10-9 = 0.000000005
Examples - Avogadro’s Number
Expresses the number of atoms in one mole of a gas
Long form:
602,000,000,000,000,000,000,000 atoms
Scientific notation:
6.02 x 10 23 atoms
Process: Count over to the left, the number of decimal places to get a number between 1 & 10
Example - Mass of an electron
Long Form:
0.000 000 000 000 000 000 000 000 000 000 911 grams
Scientific Notation:
9.11 x 10-31 grams
Process: Count over to the right the number of decimal places necessary to get a number between 1 and 10
Practice: Express the following exponentially
• 500 = 5 x 102
(count over to left 2 decimal places)
• 93,000,000 = _________________
• 0.0003 =_________________
• 0.000000024 = _________________
Exponent Relationship to Basic Unit
• Negative exponents are smaller (10 –3)
• Positive exponents are larger (10 3)
| | | | | |
If the metric system was money…
$1,000.00 $100.00 $10.00 $1.00 10 cent 1cent
Basic Unit
0.10 0.01
Why is mL and cc (cm3) the same?
• Cubic centimeter (cc or cm3) and millimeter (mL) are used interchangeably in medicine. The unit cc is a length measurement. The unit mL is a volume measure.
• A cube 1 cm long x 1 cm wide by 1 cm high (l x w x h = area) will hold 1 mL of liquid volume.
• We therefore use the units interchangeably. 1 cc or cm3 = 1 mL
1 cm length
1 cm high
1 cm deep
Cubic centimeter
The volume of this cube
is one mL.
1 mL = 1 cc = 1 cm3