RSPT 1060

1. RSPT 1060 MODULE C Lesson 5 GAS MOVEMENT

2. Objectives • At the end of this module, the student will • Define terms associated with gas movement. • Differentiate between flow, speed and velocity. • Describe how flow is measured. • Describe how velocity is measured. • Differentiate between the types of flow. • State how Poiseuille’s law is used to define the amount of pressure needed to move a fluid through a tube.

3. Objectives • At the end of this module, the student will • State the Reynold’s number where a transition from laminar to turbulent flow occurs. • Describe the effects of gas velocity, gas density, tube radius, and viscosity on Reynold’s number. • Differentiate between a low-flow oxygen delivery system and a high-flow oxygen delivery system. • Differentiate between • Jet mixing • Bernoulli principle. • Venturi principle

4. Objectives • At the end of this module, the student will • State the effect on an increase in minute volume on oxygen delivery percentage with a high-flow oxygen delivery system. • Given an FIO2, determine the air: oxygen ratio. • Given an FIO2 and an oxygen flow rate, determine the total flow. • Given an FIO2, an oxygen flow rate, and a patient’s minute volume, determines if the total flow is adequate.

5. Terms Associated with A Fluid In Motion • FLUID – A substance that is capable of flowing and that changes its shape at a steady rate when acted upon by a force tending to change its shape and to assume the shape of its container. Includes both liquids and gases. • FLOW – The bulk movement of a substance through space. • Expressed as volume of fluid moved per unit of time. • Liters per minute (L/min) • Liters per second (L/sec)

6. Terms Associated with A Fluid In Motion • SPEED – The distance traveled per unit of time. • A scalar measurement. • Miles per hour or centimeters per second. • VELOCITY–The rate at which an object changes position. • A vector quantity. • Involves not only magnitude but also direction. • Miles per hour or centimeters per second in a specified direction.

7. Flow minute • Volume/Time • Force: Occurs as a result of a pressure gradient from high energy to low energy. • The pressure difference (gradient) that exists is also known as the driving pressure. • Measurement tool: • Flow meter 5L 5L

8. Velocity distance • Distance per unit time with a direction. (vector quantity) • Force: Occurs as a result of a pressure gradient from high energy to low energy. • Measurement tool: • Ruler & watch and some mechanism to quantify direction. start finish minute

9. Velocity and Flow • Since gas flow in and out of the lungs is directional, velocity can be assessed. • Gas flow (volume/time) can also be expressed as the velocity of the gas as it relates to the cross-sectional area it is moving through. • Flow = Cross-sectional area x velocity

10. Law of Continuity • The velocity of a fluid moving through a tube varies inversely with the cross-sectional area. • As the cross-sectional area decreases, the velocity increases to maintain a constant flow. • Example: A hose that is pinched results in an increased velocity to maintain a constant flow. • This follows the conservation of mass in that the amount of a fluid entering a tube must be the same as the amount leaving the tube. • This principle is used in jet and nozzles and clinically in nebulizers and gas entrainment devices.

12. If you have a tube with a cross-sectional area of 5.08 cm2, and a gas moving at a velocity of 16.4 cm/sec, the measured flow will be 5 L/min.

13. Additional Terms Associated With A Fluid In Motion • VISCOSITY– The property of a fluid that resists the force tending to cause the fluid to flow. • This can be due to thickness of the fluid or some other cause of adhesiveness between the fluid and the container. • Water vs. Ketchup • FRICTION – Surface resistance to relative motion caused by the rubbing of one object or surface against another. • DENSITY – Mass per unit of volume (mg/L)

14. Pressure and Flow of A Fluid • The pressure exerted by a static fluid is the same at all points along a horizontal tube. • When flow occurs, the pressure drops as a tube becomes further from the source of the pressure. • Gas flow in a plumbing system.

15. No Flow

16. Flow

17. Types of flow A. Laminar B. Turbulent C. Transitional

18. Laminar Flow • Smooth movement in a parabolic pattern through a smooth tube of fixed size. • Poiseuille’s Law defines the pressure required to produce a flow under these conditions • Flow pattern found in distal airways. Velocity is greater at the center than along the walls due to friction.

19. Poiseuille’s Law P = Driving pressure (to move gas through a tube) • fluid viscosity (n) • tube length (l) • flow () • radius (r)

20. Poiseuille’s Law • Consider an endotracheal tube • If I need the same gas flow, what must happen to pressure (P) if I… • Increased length (l) needs ___________ pressure • Decreased radius (r) needs ___________ pressure • Decrease gas viscosity (n) needs ___________ pressure • If I increase the gas flow (), what must happen to pressure (P)? ___________ A. 5 L/min. B. 5 L/min.

21. Turbulent Flow • Molecules moving in many directions. • Multiple eddy currents. • Requires a greater driving pressure. • Poiseuille’s Law no longer applies. • Flow pattern found in larger airways. • Laminar flow become turbulent at a Reynold’s Number >2000. • Dimensionless number

22. Reynold’s Number v = linear velocity (distance/time) d = fluid density (weight/volume) r = tube radius (size of opening) h = fluid viscosity (thickness, stickiness)

23. v = linear velocity _____ d = fluid density ________ r = tube radius ________ h = fluid viscosity _______ Reynold’s Number What would allow gas to move freely in many directions? (more turbulent)

24. Transitional Flow • A mixture of laminar and turbulent. • Similar to what is happening in the majority of the respiratory tract.

25. Fig 6-21

26. Oxygen Therapy

27. Oxygen Equipment • If the alveolar oxygen is low (↓PAO2), the arterial oxygen (PaO2) will also be reduced. • The goal is to increase the alveolar oxygen level (PAO2)by providing supplemental oxygen to the patient. • Four Categories of Oxygen Delivery Equipment • Low Flow * • Reservoirs • Enclosures • High Flow *

28. Estimating Patient Flow Needs • One of two methods can be used to determine the patient’s inspiratory flow rate and therefore the minimum flow needed by the device. OR

29. Minute Ventilation = 8 L/min Tidal Volume = 0.4 L Respiratory Rate = 20 bpm Insp. Time = 1 sec Example: Patient Flow Needs

30. Low Flow Oxygen Delivery Systems • Devices: • Nasal Cannula • Nasal Catheter • Transtracheal Catheter (SCOOP)

31. Low Flow Systems and Inspiratory Flow • Device does not meet patient entire inspiratory flow needs. • Patient’s needs to draw in additional gas. • HAS NOTHING TO DO WITH THE FLOWMETER SETTING! • Provides low oxygen concentrations (22-45%). • Some people include “Reservoir Systems” in this category as well. • Simple masks, Partial rebreathers, Non-rebreathers, Reservoir cannulas

32. Flow Needs • Adults typically have an inspiratory flow of 24 - 30 L/min. • Low flow devices provide ¼ – 8 L/min. of 100% O2. • Flow difference must come from room air (21%) or reservoir (>21%).

33. Oxygen Concentration • Low flow devices have air & oxygen mixing at the patient’s airway. • O2 concentration is variable and depends on the patient’s respiratory pattern. • A higher O2 concentration is achieved when breathing is at a slower rate and a slow flow. • Less room air is brought into the system. • A lower O2 concentration is achieved when breathing is at a higher rate & rapid flow.

34. Oxygen Delivery Devices High-Flow Systems

35. FIO2 vs. FDO2 • The “D” stands for delivered. • Technically speaking, oxygen devices “deliver” a specific amount of oxygen. • What is actually “inspired” is related to how much air is entrained and dilutes the oxygen flow. • Like…who cares?

36. High Flow Oxygen Delivery Systems • Devices: • Air-entrainment mask (venturi) * • Air-entrainment nebulizer * • Aerosol Mask • Tracheostomy Collar • T-Bar • Face Tent • Blender • Dual Flowmeters

37. Air Entrainment Nebulizer • Oxygen source • Flow meter • Nebulizer with sterile water • Large bore tubing • Drain bag • Patient interface • Aerosol mask • Trach collar • Face tent • T-bar)

38. Fluid Entrainment • Air entrainment masks & nebulizers use a method of fluid mixing known as fluid entrainment. • First fluid flow determines the amount of a second fluid that will be drawn into the first fluid flow. 100% O2 21%Air

39. Methods of Fluid Entrainment • Jet mixing principle • Air entrainment mask • Bernoulli principle • Air entrainment nebulizers • Both principles for fluid entrainment use the concept of: • Decreasing cross sectional area • Increasing velocity of gas

40. Law of Continuity

41. Jet Mixing Principle • The net effect is an increase in total flow. • This can result in a very precise amount of oxygen and air mixing. Fig 38-13 Page 882 Source Gas (Oxygen)

42. Factors Affecting Air Entrainment • The amount of air that is entrained is dependent on two factors: • Size of the jet orifice • Size of the entrainment ports • Air-entrainment masks work by altering one of these factors.

43. Smaller jet opening causes increased velocity of main gas causing more entrainment of air. FIO2 decreases Total gas flow increases Jet Orifice Size

44. Size of Entrainment Ports • Larger ports allow more air to be entrained • FIO2 decreases • Total flow increases

45. Air:Oxygen Mixing

46. Altering FIO2 • Oxygen flow remains constant and is set by RCP with a flow meter. • Air flow changes based on: • Jet size • Port size • More air dilutes oxygen flow and decreases FIO2.

47. What will happen to FIO2when… • I decrease the size of the jet? ____________ • I increase the size of the jets? ___________ • I decrease the size of the ports? __________ • I increase the size of the ports? ___________ • I decrease the oxygen flow? _____________ • I increase the oxygen flow? ______________ • I pinch the aerosol hose? _______________ (Back pressure against air entrainment)

48. Bernoulli Effect • Fluids have three types of energy: • Potential Energy (the driving pressure) • Kinetic Energy (the energy created by a mass of fluid moving at a specific velocity) • Because the mass is never changing, it is directly proportional to the velocity of the fluid. • Pressure Energy (the energy exerted on the walls of the tube) • This radial pressure is also known as lateral wall pressure.

49. 1700 –1782 Bernoulli Effect • As fluid flows through a tube, the pressure within the tube decreases over the length. 1700 – 27 July 1782 1700 – 27 July 1782 1700 – 27 July 1782 Fig 6-24 Page 115

50. Bernoulli Effect • Fluid velocity increases as the fluid travels through a constriction.