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Techniques and Procedures I RC 170

Techniques and Procedures I RC 170. Basic Physics For Respiratory Therapist. Energy. Energy - the ability to do work Work = force X distance Kinetic energy - energy that an object possesses when it is in motion.

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Techniques and Procedures I RC 170

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  1. Techniques and Procedures IRC 170 Basic Physics For Respiratory Therapist

  2. Energy • Energy- the ability to do work • Work = force X distance • Kinetic energy- energy that an object possesses when it is in motion. • Potential energy or stored energy- the energy an object possesses because of its position. (energy of position, gravitaxl)

  3. Matter – has mass and occupies space • Atomic Theory: all matter is composed of tiny particles called atoms. • Kinetic Theory: atoms and molecules that make up matter are in constant motion Figure 1-1 States of Matter

  4. States of Matter • Solid • Limited atomic motion due to Van der Walls forces (mutual attracx) • Mostly Potential Energy, very little Kinetic • Hard to compress • Liquid • Freedom of motion - Some KE & some PE • Takes shape of container • Exhibits flow • Hard to compress • Gas • very weak attractive forces - mostly KE • Lacks Motion restrictions • Able to Flow, expand/compress

  5. Temp and Pressure scales • Temp conversions: Box 1-3, page 9 • Pressure conversions: Box 1-4, page 9 1 ATM = 760 mmHg = 14.7 psi = 1034 cmH2O 1mmHg = 1.36 cmH2O

  6. Temp Scales

  7. 1st Law of Thermodynamics • Energy can be neither created nor destroyed, only xformed in nature • Energy gains must = energy losses • Equal energy requirements to freeze/melt

  8. Change of State Boiling point: temperature at which a liquid converts to a gaseous state Figure 1-3 Temperature Scales Freezing point: temperature at which change occurs from a liquid to a solid

  9. The relationship between temperature, pressure, and kinetic activity of water molecules.

  10. Critical Pressure/Temp • Critical Temperature: T at which a gas can’t be converted back to a liquid state at any pressure (-118 °C [182 °F] for O2) • Critical Pressure: P required to convert a gas back to a liquid state at it’s critical temperature (716 psi for O2) • Gas: state of matter above it critical temperature • Vapor: state of matter below its critical temperature

  11. Change of State • Evaporation: Change from Liquid to Gas Below its boiling point • Rate of evaporation increases with • ↑ temperature, ↑surface area • ↓ PB • Sublimation: Change from solid to gas by-passing the liquid state • Condensation: conversion of a substance from a gas to a liquid.

  12. Heat Xfer • 1st law tells us that 2 objects of differing temps will xfer energy (Heat) until at equilibrium • 4 modes of heat xfer • Conduction (direct contact, solids) • Convection (direct contact, fluids) • Radiation (indirect contact) • Evaporation/Condensation • energy is xferd due to change of state • Evaporative cooling

  13. Hg Barometer Figure 1-4 A mercury barometer

  14. Aneroid Barometer Figure 1-5 An aneroid barometer

  15. Electronic Transducer

  16. Pressure and Humidity • Water Vapor Pressure: P exerted by vapor due to kinetic activity which is T dependent. (Table 1-4 page 16) • @ 37°C = 47 mmHg of VP • Absolute Humidity: actual content of water present in a sample of gas. • Relative Humidity: actual content of water present in a sample of gas relative to its total carrying capacity. Expressed in a %. (Page 103 Egan: Table 6-3)

  17. %BH & Humidity Deficit • %Body Humidity – ratio of water vapor : capacity at body Temp. (37C) • Humidity Deficit • The difference b/w capacity & content • Absolute Humidity at Body Temp • 43.8 mg/L

  18. Properties of Liquids • Pascal’s Principle • A Liquids Pressure is exerted in all directions • Pressure exerted depends on Depth (height) & Density • Viscosity • Opposing Force to a liquids flow • Directly proportional to molecular cohesive forces • Increased Temp decreases viscosity • Weakens molecular bonds

  19. Properties of Liquids Figure 1-6 A practical example of buoyancy. Archimedes’s Principle: when an object is submerged in a fluid, it will be buoyed up by a force equal to the weight of the fluid that is displaced by the object……if the weight density of the object being submerged is less than the weight density of the water, the object will float

  20. Properties of Liquids Adhesion & Cohesion Water Meniscus (Adhesion) Mercury Meniscus (Cohesion) 21

  21. Properties of Liquids Figure 1-8 The molecular basis for surface tension Surface Tension: cohesive forces between liquid molecules at a gas- liquid interface. Box 1-5 Adhesive and Cohesive forces.

  22. Properties of Liquids Laplace's Law: the pressure within a sphere is directly related to the surface tension of the liquid and inversely related to the radius of the sphere Surface Tension forces cause a liquid to have the tendency to occupy the smallest possible area, which is usually a sphere. Figure 1-9 Laplace's law.

  23. Properties of Liquids Capillary Action 24

  24. H20 DVD VIDEO MODERN MARVELS PART I

  25. Gas Laws • Boyle’s: The volume that a gas occupies when it is maintained at a constant temperature is inversely proportional to the absolute pressure exerted upon it. • With a constant temperature • If you double the Press, your volume halves • As press increases, Volume decreases & vice versa • P1V1=P2V2 P1V1=P2V2 T1 T2

  26. Boyle’s Law Figure 1-10 Boyle’s Law

  27. BOYLES ON YOU TUBE

  28. Boyle’s Law • Joule-Thompson Effect • Expansion Cooling • Purging a cylinder • Due to breaking of van der waals bonds • Compression Heating • Diesel engine

  29. Gas Laws • Charles’s: When the pressure of a gas is held constant, the volume of a gas varies directly with its absolute temperature • Under Constant pressure • Increase in temperature will increase the volume V1 =V2 T1 T2

  30. Charles’s law Figure 1-11 Charles's law

  31. CHARLES ON YOU TUBE

  32. Gay-Lussac’s law • Gay-Lussac’s: if the volume of a gas is held constant, the gas pressure rises as the absolute temperature of the gas increases. • Volume is constant • Pressure increases as temperature increases P1=P2 T1 T2

  33. Gay-Lussac’s law Figure 1-12 Gay-Lussac’s law

  34. GAY-LUSSAC ON YOUTUBE

  35. Combined Gas Law Combined Gas Law 36

  36. Dalton’s law of Partial pressures • The sum of the partial pressures of a gas mixture equals the total pressure of the system. PB= 760 mm Hg PO2 = (760) (0.21) PO2= 159 mm Hg PB= PO2+ PN2 + PCO2 + P (trace gases) PB= (760)(0.21)+ (760)(0.78)+ (760)(.003)+ (760)(.07) PB = 760 mm Hg

  37. Laws of Diffusion • Diffusion: net movement of gas molecules from a high concentration to a lower concentration. • Graham’s Law: The lower the density of the gas the more diffusible the gas. • Henry’s Law: The higher the partial pressure of a gas the quicker it will dissolve in a liquid.

  38. Fick’s law of Diffusion • Fick’s: the rate of diffusion of a gas in a gaseous medium is proportional to the gradient of their concentration, the surface area available for diffusion, and inversely proportional to the thickness of the membrane. • The higher the concentration of the gas the quicker it dissolves.

  39. Fick’s law of diffusion Figure 1-14 Fick’s law of diffusion

  40. Pre-class Survey! • In mmHg, what is the pressure exerted by water in air @ 37’C? • In mg/L, What is the absolute content of water vapor in air @ 37’C? • What is the Cylinder Color for Oxygen? • What is the Cylinder factor of an E tank?

  41. Fluid Mechanics • Laminar flow: “smooth flow” page 18 fig.1-5 • Viscosity of the gas • Length of the tubing • Radius of the tube • Turbulent flow: “rough flow” chaotic disorderly pattern or layers. ↑velocity + • Transitional flow: mixture of laminar and turbulent flows.

  42. Figure 1-15 Three patterns of flow: laminar, turbulent, and transitional

  43. Poiseuille’s Law (Laminar flow) • Driving pressure plus resistance to flow • Viscosity of the fluid/gas • More viscous the greater the pressure needed • Length of the tube • Longer the tube greater the pressure needed • Radius of the tube (4th power of the radius) • ↓ radius by ½ will ↑ resistance by 16 times • Smaller the radius the greater the pressure needed • Reynolds’s number: Turbulent flow occurs when Reynolds’s number exceeds 2000.

  44. Modern Marvels Part II

  45. Press in flowing fluids • STATIC FLOWING

  46. Bernoulli Principle • Bernoulli’s: as the forward velocity of a gas (or Liquid) moving through a tube increases, the lateral wall pressure of the tube will decrease. • Drop in lateral fluid pressure is directly related to the increase in fluid velocity. • Law of Continuity: fluids velocity varies inversely with x-sectional area

  47. Figure 1-16 The Bernoulli principle

  48. Venturi Principle • The lateral pressure drop that occurs as the fluid flows through a constriction in a tube can be restored to the pre-constriction pressure if there is a gradual dilation in the tube distal to the constriction. • This also helps to prevent turbulent flow.

  49. Entrainment port Figure 1-17 The Venturi principle

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