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Clinical calculations

Clinical calculations. Dimensional analysis. = label factor method = unit-conversion method Computation method whereby one particular unit of measurement is converted to another unit of measurement by use of a conversion factor or factors. Answer unit. Starting factor. Conversion factors.

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Clinical calculations

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  1. Clinical calculations

  2. Dimensional analysis = label factor method = unit-conversion method • Computation method whereby one particular unit of measurement is converted to another unit of measurement by use of a conversion factor or factors

  3. Answer unit Starting factor Conversion factors

  4. Steps in Dimensional Analysis • Determining the starting factor and answer unit • Formulating a conversion equation • Solving the convertion equation

  5. Step I: Determining the Starting Factor and Answer Unit Example: How many inches are there in 29 feet? • 29 feet – known quantity, which have to be converted – starting factor • The desired unit – answer unit(in)

  6. Step II: Formulating the Conversion Equation • Conversion factors – bridges leading from starting factor to the desired unit • The numerator and denominator must be of equivalent value • The fraction always is equal to 1

  7. Step II: Formulating the Conversion Equation • 1 hr = 60 min – equivalents • 1 hr/60 min = 60 min/1 hr - conversion factors

  8. Step II: Formulating the Conversion Equation Example: Find the number of minutes in 90 seconds Equivalents: 1 min=60 sec Conversion Equation: Starting Convertion Answer factor factor unit 90 sec × 1 min/60 sec = ___ min

  9. Solving the conversion equation Example: Find the number of yards in 1.5 miles • Equivalents: 1 mi = 5280 ft; 3 ft = 1 yd • Equation: 1.5 mi × 5280ft/1 mi × 1yd/3ft The identical units must be placed diagonally (in the numerator of one factor and in the denominator of the factor immediately following)

  10. Solving the conversion equation • 1.5 mi × 5280ft/1 mi × 1yd/3ft 1.5 × 5280/1 × 1 yd/3 (1.5 × 5280)/3=2640 yd

  11. Systems of Measurement • The metric system • The apothecaries’ system • The household system

  12. Metric System of Measurement • Based on the decimal system • Basic units: • Gram – for weight • Liter – for volume • Meter – for length

  13. Metric Units and Abbreviations • Weight • Gram g • Miligram mg • Microgram mcg (μg) • Kilogram kg Volume Liter L Milliliter mL (cc) Length Meter m Centimeter cm Millimeter mm

  14. Apothecaries’ System of Measurement • The measures are approximations • Roman numerals are often used • Fractions are used (ss = ½) • Symbol for a unit of measure is written before the quantity – gr viiss = gr VIIss • A combination of Arabic numerals • and fractions can be used - gr 7 ½

  15. Apothecaries’ System of Measurement • Weight • The basic unit is grain (gr) gr 15 = 1 g 60 mg = gr 1 • Dram (medication cup) dr • Ounce – oz • Pound (lb) = 16 oz

  16. Apothecaries’ System of Measurement • Volume • The smallest unit is the minim (m) • Dram (dr) dr 1= 4 mL • Ounce (oz) = 30 mL • Pint (pt) pt 1 =oz 16 = 500 mL • Quart (qt) qt 1 = pt 2= 1,000 mL

  17. Household System • Some of the units for liquid measures are the same as those in the apothecaries’ (pint and quart) • There are no standart rules for expressing household measures • Standart cookbook abbreviations, Arabic numerals and fractions are used

  18. Household Units • Drop (gtt) • Teaspoon (t, tsp) • Tablespoon (T, tbs) 1 tbs = 3 tsp • Cup (C) 1 C = 16 tbs • Pint (pt) 1 pt = 2 C • Quart (qt) 1 qt = 2 pt • 1 glassful = 8 ounces

  19. Apothecaries’/Household/Metric Equivalents • 1 ounce (oz) = 30 mL • 1 dram (dr) = 4 mL • 1 tablespoon (T or tbs) = 15 mL • 1 teaspoon (t or tsp) = 5 mL • 1 cup = 240 mL (8 ounces) • 1 pint (pt) = 500 mL (16 ounces) • 1 quart (qt) = 1,000 mL (32 ounces) • 15 or 16 minims (m) = 1 mL • 1 kg = 2.2 lb

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