Physical Principles of Respiratory Care

1. Physical Principles of Respiratory Care Egan Chapter 6

2. Physical Principles of Respiratory Care • States of Matter • Change of State • Gas Behavior Under Changing Conditions • Fluid Dynamics

3. II. Change of State • Liquid-Solid Phase Changes • Melting • Freezing • Properties of Liquids • Pressure in Liquids • Buoyancy (Archimedes’ Principle) • Viscosity • Cohesion and Adhesion • Surface Tension • Capillary Action • Liquid-Vapor Phase Changes • Boiling • Evaporation, Vapor Pressure, and Humidity • Properties of Gases • Kinetic Activity of Gases • Molar Volume and Gas Density • Gaseous Diffusion • Gas Pressure • Partial Pressure (Dalton’s Law) • Solubility of Gases in Liquids (Henry’s Law)

4. II. Change of State • Liquid-Solid Phase Changes • Melting • Freezing http://www.youtube.com/watch?v=j2KZmRIKea8 Start at 3:15

5. A. Liquid-Solid Phase Changes • Melting ?When a solid is heated, what happens to its kinetic energy? • What happens to its intermolecular forces?

6. A. Liquid-Solid Phase Changes 2. Freezing ? When a liquid is cooled, what happens to its kinetic energy? • What happens to its intermolecular forces?

7. A. Liquid-Solid Phase Changes Intermolecular forces

8. A. Liquid-Solid Phase Changes • Melting and Boiling • Melting Point: • The temperature at which a solid converts to a liquid • Boiling Point • The temperature at which a liquid converts to the gaseous state

9. A. Liquid-Solid Phase Changes • Melting and Boiling • Latent Heat: • The amount of heat needed for a substance to change its state of matter • Latent heat of fusion: • The amount of heat needed to change a solid to a liquid • Latent heat of vaporization • The amount of heat needed to change a liquid to a gas

10. A. Liquid-Solid Phase Changes Latent heat of vaporization Steam Latent heat of fusion Water Ice

11. II. Change of State • Properties of Liquids • Pressure in Liquids • Buoyancy (Archimedes’ Principle) • Viscosity • Cohesion and Adhesion • Surface Tension • Capillary Action

12. B. Properties of Liquids • Liquid Oxygen • http://www.youtube.com/watch?v=ndtmfDoI8PM

13. B. Properties of Liquids • Liquid molecules also possess attractive forces • but these forces are much weaker in liquids than in solids • Liquid molecules have greater freedom of movement and possess more KE than solids • This is why liquids take the shape of their container • And are capable of flow • Liquids cannot be easily compressed

14. 1. Pressure in Liquids Is the same at any specific depth, regardless of the container’s shape Is exerted equally in all directions B. Properties of Liquids

15. B. Properties of Liquids 1. Pressure in Liquids • Pascal’s Principle: • A confined liquid transmits pressure equally in all directions

16. B. Properties of Liquids 1. Pressure in Liquids • Pascal’s Principle • Downward

17. B. Properties of Liquids 1. Pressure in Liquids • Liquids are capable of flow • Pascal’s Principle • Sideways

18. B. Properties of Liquids 1. Pressure in Liquids • Pascal’s Principle • Upward http://www.youtube.com/watch?v=iD55ynlUH8g http://www.youtube.com/watch?v=UpwLwP0pmwk

19. B. Properties of Liquids • Pressure in Liquids • Clinical Application • Heart Failure

20. B. Properties of Liquids • Pressure in Liquids • Clinical Application • Using an air or water mattress to prevent the development of bed soars

21. B. Pressure in Liquids 2. Buoyancy (Archimedes’ Principle) • Buoyancy occurs because the pressure below a submerged object always exceeds the pressure above it

22. B. Pressure in Liquids 2. Buoyancy (Archimedes’ Principle) • According to Archimedes • This buoyant force must equal the weight of the fluid displaced buy the object http://www.youtube.com/watch?v=mhJ5Ybt7L2k http://www.youtube.com/watch?v=vJ36urazDu4&list=PLB76160897CFFC3F4&index=8&feature=plpp_video

23. B. Pressure in Liquids 2. Buoyancy (Archimedes’ Principle) • Gases also exert buoyant force • Buoyancy helps keep solid particles suspended in gases • These suspensions, called aerosols, play an important role in respiratory care.

24. B. Properties of Liquids 3. Viscosity • Internal force that opposes flow of a fluid, either liquids or gases • Fluid’s viscosity is directly proportional to cohesive forces between its molecules • The stronger the cohesive forces, the greater the fluid viscosity • Heart must use more energy when blood viscosity increases, as occurs in polycythemia

25. B. Properties of Liquids 3. Viscosity • Clinical Application • The greater the viscosity of a fluid, the more energy is needed to make it flow • The heart must perform more work when blood viscosity increases • Polycythemia: an increase in red blood cells • Polycythemia is common in patients with chronic bronchitis

26. B. Properties of Liquids 4. Cohesion and adhesion • The attractive force between like molecules is cohesion. • The attractive force between unlike molecules is adhesion.

27. Cohesion and Adhesion Water Concave meniscus • Adhesion > Cohesion

28. Cohesion and Adhesion Mercury Convex meniscus • Cohesion > Adhesion

29. B. Properties of Liquids 5. Surface Tension • a force exerted by like molecules at a liquid’s surface • The cohesive forces between liquid molecules are responsible for this phenomenon

30. B. Properties of Liquids 5. Surface Tension

31. B. Properties of Liquids 5. Surface Tension

32. B. Properties of Liquids 5. Surface Tension • Explains why liquid droplets and bubbles retain a spherical shape

33. B. Properties of Liquids 5. Surface Tension • In bubbles

34. B. Properties of Liquids 5. Surface Tension • Laplace’s Law • The pressure within a sphere • Varies directly with the surface tension of the liquid • As the surface tension of the liquid increases, the internal pressure increases • Varies inversely with its radius • As the droplet becomes smaller and the radius decreases, the internal pressure increases • P = 4ST r

35. B. Properties of Liquids 5. Surface Tension • Laplace’s Law http://www.youtube.com/watch?v=RAmx4_G9XsQ

36. B. Properties of Liquids 5. Surface Tension in alveoli

37. Surface Tension • Surface tension in alveoli • Alveoli with increased surface tension • Have a greater tendency to collapse • Require greater distending pressure to maintain their volume

38. B. Properties of Liquids 5. Surface Tension in alveoli • Clinical Application: • Atelectasis

39. B. Properties of Liquids 5. Surface Tension • Normal CXR after the application of Continuous Positive Airway Pressure (CPAP)

40. B. Properties of Liquids 5. Surface Tension • The lung reduces surface tension of alveoli by the production of a complex surface tension reducing chemical mixture called SURFACTANT http://www.youtube.com/watch?v=Gpcbetob4p4

41. B. Properties of Liquids 5. Surface Tension • Clinical Application • The first breath of life

42. B. Properties of Liquids 5. Surface Tension • Artificial surfactant administration in Infant Respiratory Distress Syndrome

43. B. Properties of Liquids 5. Surface Tension • Clinical Application • Liquid Ventilation http://www.youtube.com/watch?v=2OxstD2jN08

44. B. Properties of Liquids 6. Capillary Action • A phenomenon in which a liquid in a small tube moves upward, against gravity

45. B. Properties of Liquids 6. Capillary Action http://www.youtube.com/watch?v=mdkeZbm0cCI

46. B. Properties of Liquids 6. Capillary Action • Clinical Examples • Capillary blood stick http://www.youtube.com/watch?v=q5J1cCyrASs

47. B. Properties of Liquids 6. Capillary Action • Clinical Examples • Absorbent wick humidifiers

48. C. Liquid-Vapor Phase Changes • Boiling • Evaporation, Vapor Pressure, and Humidity

49. C. Liquid-Vapor Phase Changes • Liquid to vapor phase changes (vaporization) • 2 types of vaporization • Boilingheating liquid to temperature at which its vapor pressure exceeds atmospheric pressure • Boiling point of most liquefied gases is very low • Liquid oxygen boils at -183°C • Evaporationwhen liquid changes into gas at temperature below its boiling point • Evaporation requires heat. The heat energy required for evaporation comes from the air next to the water surface. As the surrounding air loses heat energy, it cools. This is the principle of evaporative cooling, which was previously described. • Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor) • Molecular water exerts pressure called water vapor pressure • Temperature influences evaporation most • The warmer the air, the more vapor it can hold

50. C. Liquid-Vapor Phase Changes 2. Evaporation, Vapor Pressure and Humidity • Evaporation: the change in state of substance from a liquid to a gaseous state below its boiling point. • Molecular water exerts a pressure called the water vapor pressure