1. RSPT 1060 Module C-7 THERMODYNAMICS and HUMIDITY

2. OBJECTIVES At the end of this module, the student should be able to… –Define terms associated with thermodynamics. –List the following on the Fahrenheit, Celsius, and Kelvin temperature scales: Freezing point Boiling point Body temperature Absolute zero.

3. OBJECTIVES At the end of this module, the student should be able to… –Convert between the following scales: –Fahrenheit and Celsius temperature scales. –Celsius and Kelvin temperature scales. –Define heat. –Differentiate between a calorie and a kilocalorie.

4. OBJECTIVES At the end of this module, the student should be able to… –State the number of kilocalories obtained for 1 gram of each of the following substances: Carbohydrate Fat Protein –Compare and contrast the four methods of heat transfer.

5. OBJECTIVES At the end of this module, the student should be able to… –State the water vapor pressure of alveolar gas in the following units: mm Hg –mg/L Differentiate between the following: Absolute humidity Relative humidity Humidity deficit

6. OBJECTIVES At the end of this module, the student should be able to… –Explain the relationship between surface area and evaporation. –Given appropriate information and conversion factors, determine the relative humidity of a gas. –Describe how properties of gases may change under extreme temperatures and pressures. –Describe what the critical point is and how it is used in gas therapy.

7. OBJECTIVES At the end of this module, the student should be able to… –Given appropriate information, determine the duration of use of a liquid cylinder of gas. –Given appropriate information determine the duration of use of a gaseous cylinder of gas

8. Practice Sibberson’s Practical Math For RC: –Ch4: Inspiratory Flow Rates, Sample Problems First & Second Set, pgs. 47-49. Practice problems, pgs 53-54 –Ch 12: I:E Ratio, Sample Problems Eighth Set, pgs 146-147 Practice Problems, pg. 156

9. Temperature Definitions: –One method of quantifying matter. –How cold or hot an object is. –The amount of Kinetic activity.

10. Measurement Systems °F = Fahrenheit (British) °C = Celsius (Centigrade) (European) °K= Kelvin (Standard International) °R = Rankine (used in engineering; not in medicine) http://www.dandantheweatherman.com/Bereklauw/ Celsius.htm

11. Other Temperature Scales Delisle (°D) –Russian –2,400 grauations –Zero as boiling; 100 as freezing Newton (°N) –Initially “cold air in winter” to “glowing coals in the kitchen fire” –Zero as melting snow; 33 as boiling water Réaumur (°Re or °R) –French –Zero as freezing; 80 as boiling. –Still in use in some cheese manufactuing Rǿmer (°Rǿ) –Danish astronomer –Zero was freezing brine; 60 as boiling water.

12. Body Temperature Normal body temperature is 37°C (98.6°F). –Or is it? http://www.amstat.org/publications/jse/v4n2/da tasets.shoemaker.html#mackowiak http://www.amstat.org/publications/jse/v4n2/da tasets.shoemaker.html#mackowiak Exercise can increase it to 100 - 103° F. Individual daily patterns may cause 1 - 3 degree change in a day. –Called diurnal variation. –Morning people peak temp by mid morning. –Night people peak in evening.

13. Temperatures to Know °F°F°C°C°K°K Absolute Zero-460-2730 Freezing of Water 320273 Body Temperature 98.637310 Boiling of Water 212100373

14. Figure 6-2, page 95

15. Conversion We will be doing conversions from one system to the other. The rules for rearranging formulas, canceling and (+) & (-) numbers will be used. Conversions will be used at the patient bedside, in blood gas labs and pulmonary function labs

16. FORMULAS FOR TEMPERATURE CONVERSION ° F = 1.8( ° C) + 32 (Using a decimal) ° F = 9/5( ° C) + 32 (Using a fraction) ° C =.555( ° F-32) (Using a decimal) ° C = 5/9( ° F-32) (Using a fraction) 5 ° F = 9 ° C + 160 ° K = ° C + 273 ° C = ° K - 273 ° F - ° C - ° K Convert F into C then into K ° K - ° C - ° F Convert K into C then into F

17. Using the formula: 5°F = 9°C + 160 212 °F = __________ °C

18. Practice: The highest land temperature ever recorded was 136°F in Al Aziziyah, Libya, on September 13, 1922. What is this temperature on the Celsius scale?

19. Heat Heat is a form of kinetic energy that is transferred from a hotter object to a colder object when the two come in contact. Most common form of energy is heat energy. Many chemical reactions produce heat energy.

20. How is heat energy measured? Metric –calorie (cal) or the amount of heat needed to raise 1 gram of water 1 degree Celsius –On food label 1 kilocalorie (Cal or kcal) = 1,000 calories (cal) S.I. –1 cal. = 4.184 joules

21. EXAMPLE: 12g of sugar when burned yields 45 Cal (or 45 kilocalories or 45,000 cal) of heat energy –Adult males need 3,000 Cal/day –Adult females need 2,200 Cal./day Food calories: –1 g carbohydrate yields 4 kcal –1 g fat yields 9 kcal –1 g protein yields 4 kcal

22. “Specific” heat The amount of heat that will raise the temperature of 1 gram of a substance 1°C –Water = 1 cal/g x ° C –Gold = 0.031 cal/g x ° C –Iron = 0.106 cal/g x ° C The body is 60% water so it takes a larger transfer of heat to change body temperature. This is why body temperature remains relatively stable.

23. How does heat transfer? Heat moves from an object of higher temperature to an object of lower temperature in four ways. Conduction Convection Radiation Evaporation

24. Conduction Transfer of heat by direct contact Solid objects like metal conduct heat away quickly thermal conductivityThey have a high thermal conductivity and often feel cool to the touch as they remove heat from your hand.

25. Convection Transfer of heat by mixing of fluid molecules Gases or liquids mixing in currents or forced air heating Convection oven

26. Radiation Transfer of heat to a cooler, distant object. No direct physical contact Conventional oven

27. Evaporation Form of vaporization where liquid turns to gas and heat is taken away from the air surrounding the liquid

28. EXAMPLE: Newborn babies are kept warm by –Drying them off (reduces evaporation) –Placing them in a preheated isolette or warmer (reduces radiation & conduction) –Keeping them out of drafty areas (reduces convection).

29. Humidity

30. Definitions & Measurements Humidity – Water in a gas or molecular form, also called a vapor. Measurement: hygrometer or psychrometer –Vapor Pressure (mm Hg) –Water Content (mg/L) (see chart provided)

31. TEMPERATURE (C) WATER VAPOR PRESSURE (mmHg) WATER CONTENT (mg/L) ATPS to BTPS Correction Factor 2017.517.31.102 2118.618.41.096 2219.819.41.091 2321.120.61.085 2422.421.81.080 2523.823.01.075 2625.224.41.068 2726.725.81.063 2828.327.21.057 2930.028.81.051 3031.830.41.045 3133.732.01.039 3235.733.81.032 3337.735.61.026 3439.937.61.020 3542.239.61.014 3644.041.71.007 3747.043.81.000

32. Definitions actualAbsolute humidity – the actual measurement of the amount of water in a gas. (mg/L) –This is the content. Water vapor pressure – the pressure exerted by water in the gaseous form (mm Hg)

33. Definition Saturated - A gas containing the maximum amount of water it can possibly hold (100% humidity) %Relative humidity %Body Humidity –Where the capacity is 43.8 mg/L

34. Relative Humidity Calculations A gas at 26° C with an absolute humidity of 19 mg/L

35. Relative Humidity Calculations A gas at 35° C with an absolute humidity of 30 mg/L

36. Body Humidity Calculations Body humidity is ALWAYS measured at 43.8 mg/L & 37 ° C A gas with an absolute humidity of 19 mg/L

37. Body Humidity Calculations A gas with an absolute humidity of 30 mg/L.

38. Humidity Deficit humidity deficitThe difference between the absolute humidity and the body humidity (43.8 mg/L @ 37° C) in mg/L is called the humidity deficit. This is the amount of humidity the tracheobronchial tree has to make up to attain 43.8 mg/L and 47 mm Hg at 37° C at the Isothermal Saturation Boundary (ISB). Humidity Deficit (HD) = Absolute Humidity - Body Humidity

39. Isothermic Saturation Boundary normally 5 cm below carina where temp. needs to be 37° C with a RH of 100% 37 ° C RH 100% 43.8 mg/L 47 mmHg

40. Humidity Deficit Calculations Body humidity = always 47 mmHg or 43.8 mg/L @ 37° C Humidity Deficit (HD) = Absolute Humidity- Body Humidity Gas at 26°C with absolute humidity of 19 mg/L.

41. Humidity Deficit Calculations Body humidity = always 47 mmHg or 43.8 mg/L @ 37° C Humidity Deficit (HD) = Absolute Humidity- Body Humidity Gas at 35° C with absolute humidity of 30 mg/L.

42. AARC CPG on Humidification During Mechanical Ventilation The AARC CPG recommends that inspired gas be warmed to 33 + 2° C and with a minimum of 30 mg/L of water vapor.

43. More Practice Sibberson –See charts on pages 24 & 25 –Chapter 7 Sample Problems First & Second Set Practice Problems 1-30

44. Factors affecting humidity levels Temperature Pressure (altitude) Surface Area Exposure Time

45. Temperature As temperature increases, the rate of evaporation increases and more water moves into gas as well as the gas can hold more water.

46. CAPACITY vs. CONTENT A, The effect of increasing capacity without changing content, as when heating a saturated gas. B, The effect of decreasing capacity, as when cooling a gas. Warm gas can hold more water. Cooling gas forms condensation. A B

47. TEMPERATURE (C) WATER VAPOR PRESSURE (mmHg) WATER CONTENT (mg/L) ATPS to BTPS Correction Factor 2017.517.31.102 2118.618.41.096 2219.819.41.091 2321.120.61.085 2422.421.81.080 2523.823.01.075 2625.224.41.068 2726.725.81.063 2828.327.21.057 2930.028.81.051 3031.830.41.045 3133.732.01.039 3235.733.81.032 3337.735.61.026 3439.937.61.020 3542.239.61.014 3644.041.71.007 3747.043.81.000

48. Gases leaving a standard heated humidifier are cooled en route to the patient. Although the gas remains saturated (100% relative humidity [RH]), cooling reduces its water vapor capacity and condensation forms.

49. Pressure As pressure increases (decreases in altitude), rate of evaporation decreases. This is why water boils (evaporates) at a lower temperature as you rise in altitude. –But also why cooking time is longer!

50. Cooking = Temperature x Time LOCATIONBAROMETRIC PRESSURE BOILING POINT OF WATER MICHIGAN 750 mm Hg100° C DENVER 640 mm Hg95° C (increase cooking time – not as hot when boiling) MOUNT EVEREST 235 mm Hg70° C (increase cooking time)

51. Surface Area As you increase surface area (such as an increase in number and reduction in size of bubbles), the rate of evaporation will increase.

52. Lots of tiny bubbles increase surface area

53. Exposure Time An increase in exposure time means there is more time for evaporation to occur and means an increase in evaporation rate. A close monitoring of water level in the humidifier is important.

54. Keep water levels high for increased exposure time

55. Adverse effects of poor humidity Decreased ciliary motility Airway irritation Increased mucus production Thickening of secretions Inspissated secretions (mucus plugging) Destruction of airway epithelium Atelectasis

57. Critical Points Every liquid has a temperature, above which, the kinetic activity is too great to keep the molecules at the surface from breaking free. –This is the critical temperature. The pressure at which equilibrium between the liquid and gaseous phases at the critical temperature is known as the critical pressure. Together they are known as the critical point of a substance.

58. Importance of Critical Point This is the point at which a substance can no longer be held in the liquid phase, and conversion to a gas occurs. In order to liquefy a gas (like oxygen) you have to two choices: –Cool it to below its boiling point (-183° C or - 297° F) – or – –Cool it to its critical point (-118.8° C or -181° F and 49.7 atmospheres) The more you cool it, the less pressure is needed.

59. Storage of Oxygen as a Liquid Bulk oxygen systems store oxygen as a gas and allow the temperature to slowly rise resulting in gaseous oxygen to escape. For portable liquid systems, the amount of oxygen in the cylinder must be determined by weight. –1 L of liquid oxygen weighs 2.5 pounds and produces 860 L of gaseous oxygen when allowed to warm and expand. –Once you determine the amount of gas in Liters, you can determine the duration of the cylinder by dividing by the gas flow rate.

60. Liquid Oxygen Systems

61. Method to Determine Liquid Oxygen System Duration You have a patient using a liquid oxygen cylinder who is planning to go Christmas shopping. She reports that her cylinder weighs 5 pounds and she has it connected to a nasal cannula running at 2 L/min. How long will the cylinder last?

62. Duration of Gaseous Cylinder Whole lot easier! –So long as you know the cylinder factor…For oxygen: E: 0.28 H: 3.14

63. Method to Determine Liquid Oxygen System Duration You have a patient using a liquid oxygen cylinder who is planning to go Christmas shopping. She reports that her E cylinder has 1,500 psig in it and she has it connected to a nasal cannula running at 2 L/min. How long will the cylinder last?

64. Practice Problems Sibberson –2 nd Set – Page 37 –3 rd Set – Page 40 –4 th Set – Page 41 –Practice Exercises – Pages 41 – 45