RSPT 1060

MODULE CMODULE C

Lesson 5 Lesson 5

GAS MOVEMENTGAS MOVEMENT

Objectives

• At the end of this module, the student At the end of this module, the student willwill

– Define terms associated with gas movement.Define terms associated with gas movement.– Differentiate between flow, speed and velocity.Differentiate between flow, speed and velocity.– Describe how flow is measured.Describe how flow is measured.– Describe how velocity is measured.Describe how velocity is measured.– Differentiate between the types of flow.Differentiate between the types of flow.– State how Poiseuille’s law is used to define the State how Poiseuille’s law is used to define the

amount of pressure needed to move a fluid amount of pressure needed to move a fluid through a tube.through a tube.

Objectives

• At the end of this module, the student At the end of this module, the student willwill

– State the Reynold’s number where a transition State the Reynold’s number where a transition from laminar to turbulent flow occurs.from laminar to turbulent flow occurs.

– Describe the effects of gas velocity, gas density, Describe the effects of gas velocity, gas density, tube radius, and viscosity on Reynold’s number. tube radius, and viscosity on Reynold’s number.

– Differentiate between a low-flow oxygen delivery Differentiate between a low-flow oxygen delivery system and a high-flow oxygen delivery system.system and a high-flow oxygen delivery system.

– Differentiate between Differentiate between • Jet mixing Jet mixing • Bernoulli principle.Bernoulli principle.• Venturi principleVenturi principle

Objectives

• At the end of this module, the student willAt the end of this module, the student will– State the effect on an increase in minute volume State the effect on an increase in minute volume

on oxygen delivery percentage with a high-flow on oxygen delivery percentage with a high-flow oxygen delivery system.oxygen delivery system.

– Given an FGiven an FIIOO22, determine the air: oxygen ratio., determine the air: oxygen ratio.

– Given an FGiven an FIIOO22 and an oxygen flow rate, determine and an oxygen flow rate, determine the total flow.the total flow.

– Given an FGiven an FIIOO22, an oxygen flow rate, and a patient’s , an oxygen flow rate, and a patient’s minute volume, determines if the total flow is minute volume, determines if the total flow is adequate.adequate.

Terms Associated with A Fluid In Motion

• FLUIDFLUID – A substance that is capable of flowing – A substance that is capable of flowing and that changes its shape at a steady rate when and that changes its shape at a steady rate when acted upon by a force tending to change its acted upon by a force tending to change its shape and to assume the shape of its container. shape and to assume the shape of its container. Includes both liquids and gases.Includes both liquids and gases.

• FLOWFLOW – The bulk movement of a substance – The bulk movement of a substance through space. through space. – Expressed as volume of fluid moved per unit of Expressed as volume of fluid moved per unit of

time.time.• Liters per minute (L/min)Liters per minute (L/min)• Liters per second (L/sec)Liters per second (L/sec)

Terms Associated with A Fluid In Motion

• SPEED – SPEED – The distance traveled per unit of time.The distance traveled per unit of time.– A scalar measurement.A scalar measurement.– Miles per hour or centimeters per second.Miles per hour or centimeters per second.

• VELOCITYVELOCITY –The rate at which an object changes –The rate at which an object changes position. position. – A vector quantity.A vector quantity.– Involves not only magnitude but also direction. Involves not only magnitude but also direction. – Miles per hour or centimeters per second in a Miles per hour or centimeters per second in a

specified direction.specified direction.

Flow

• Volume/TimeVolume/Time

• Force: Occurs as a result of a Force: Occurs as a result of a pressure pressure gradientgradient from high energy to low energy. from high energy to low energy.– The pressure difference (gradient) that exists is also The pressure difference (gradient) that exists is also

known as the known as the driving pressuredriving pressure..

• Measurement tool:Measurement tool:– Flow meterFlow meter

5L 5L

minute

Velocity

• Distance per unit timeDistance per unit time with a direction. with a direction. (vector quantity) (vector quantity)

• Force: Occurs as a result of a Force: Occurs as a result of a pressure pressure gradientgradient from high energy to low energy. from high energy to low energy.

• Measurement tool:Measurement tool:– Ruler & watch and some mechanism to quantify Ruler & watch and some mechanism to quantify

direction.direction.

start finishminute

distance

Velocity and Flow

• Since gas flow in and out of the lungs is Since gas flow in and out of the lungs is directional, velocity can be assessed.directional, velocity can be assessed.

• Gas flow (volume/time) can also be Gas flow (volume/time) can also be expressed as the velocity of the gas as it expressed as the velocity of the gas as it relates to the cross-sectional area it is relates to the cross-sectional area it is moving through.moving through.– Flow = Cross-sectional area x velocityFlow = Cross-sectional area x velocity

Law of Continuity• The velocity of a fluid moving through a tube The velocity of a fluid moving through a tube

varies inversely with the cross-sectional area.varies inversely with the cross-sectional area.– As the cross-sectional area decreases, the As the cross-sectional area decreases, the

velocity increases to maintain a constant flow.velocity increases to maintain a constant flow.– Example: A hose that is pinched results in an Example: A hose that is pinched results in an

increased velocity to maintain a constant flow.increased velocity to maintain a constant flow.• This follows the conservation of mass in that the This follows the conservation of mass in that the

amount of a fluid entering a tube must be the same as amount of a fluid entering a tube must be the same as the amount leaving the tube.the amount leaving the tube.

– This principle is used in jet and nozzles and This principle is used in jet and nozzles and clinically in nebulizers and gas entrainment clinically in nebulizers and gas entrainment devices.devices.

• If you have a tube with If you have a tube with a cross-sectional area a cross-sectional area of 5.08 cmof 5.08 cm22, and a gas , and a gas moving at a velocity of moving at a velocity of 16.4 cm/sec, the 16.4 cm/sec, the measured flow will be measured flow will be 5 5 LL//minmin..

Additional Terms Associated With A Fluid In Motion

• VISCOSITYVISCOSITY – The property of a fluid that resists the – The property of a fluid that resists the force tending to cause the fluid to flow. force tending to cause the fluid to flow. – This can be due to thickness of the fluid or some other cause This can be due to thickness of the fluid or some other cause

of adhesiveness between the fluid and the container.of adhesiveness between the fluid and the container.– Water vs. KetchupWater vs. Ketchup

• FRICTIONFRICTION – – Surface resistance to relative motion Surface resistance to relative motion caused by the rubbing of one object or surface against caused by the rubbing of one object or surface against another.another.

• DENSITYDENSITY – – Mass per unit of volume (mg/L)Mass per unit of volume (mg/L)

Pressure and Flow of A Fluid

• The pressure exerted by a static fluid is The pressure exerted by a static fluid is the same at all points along a horizontal the same at all points along a horizontal tube.tube.

• When flow occurs, the pressure drops as When flow occurs, the pressure drops as a tube becomes further from the source a tube becomes further from the source of the pressure.of the pressure.– Gas flow in a plumbing system.Gas flow in a plumbing system.

No Flow

Flow

Types of flow

A. LaminarA. Laminar

B. TurbulentB. Turbulent

C. TransitionalC. Transitional

Laminar Flow

• Smooth movement in a Smooth movement in a parabolicparabolic pattern pattern through a smooth tube of fixed size.through a smooth tube of fixed size.

• Poiseuille’s LawPoiseuille’s Law defines the defines the pressurepressure required to produce a flow under these required to produce a flow under these conditionsconditions

• Flow pattern found in distal airways.Flow pattern found in distal airways.

Velocity is greater at the center than along the walls due to friction.

Poiseuille’s Law

P = Driving pressure P = Driving pressure (to move gas through a tube)(to move gas through a tube)– fluid viscosity (n)fluid viscosity (n)– tube length (tube length (ll))– flow (flow ())– radius (r)radius (r)

4

8

r

nVP

Poiseuille’s Law• Consider an endotracheal tubeConsider an endotracheal tube

• If I need the same gas flow, what must happen to If I need the same gas flow, what must happen to pressure (P) if I… pressure (P) if I… – Increased length (Increased length (ll) needs ___________ pressure) needs ___________ pressure– Decreased radius (r) needs ___________ pressureDecreased radius (r) needs ___________ pressure– Decrease gas viscosity (n) needs ___________ pressureDecrease gas viscosity (n) needs ___________ pressure

• If I increase the gas flow (If I increase the gas flow (), what must happen to ), what must happen to pressure (P)? ___________pressure (P)? ___________

A.

5 L/min.

B.

5 L/min.

Turbulent Flow• Molecules moving in many directions.Molecules moving in many directions.

– Multiple eddy currents.Multiple eddy currents.

• Requires a greater driving pressure.Requires a greater driving pressure.– Poiseuille’s Law no longer applies.Poiseuille’s Law no longer applies.

• Flow pattern found in larger airways.Flow pattern found in larger airways.• Laminar flow become turbulent at a Reynold’s Laminar flow become turbulent at a Reynold’s

Number >2000.Number >2000.– Dimensionless numberDimensionless number

h

2rdNumbers Reynold'

Reynold’s Number

v = linear velocity (distance/time)v = linear velocity (distance/time)

d = fluid density (weight/volume)d = fluid density (weight/volume)

r = tube radius (size of opening)r = tube radius (size of opening)

h = fluid viscosity (thickness, h = fluid viscosity (thickness, stickiness)stickiness)

h

2rdNumbers Reynold'

Reynold’s Number

v = linear velocity _____v = linear velocity _____

d = fluid density ________d = fluid density ________

r = tube radius ________r = tube radius ________

h = fluid viscosity _______h = fluid viscosity _______

What would allow gas to move freely in many directions? (more turbulent)

h

2rdNumbers Reynold'

Transitional Flow

• A mixture of laminar and turbulent.A mixture of laminar and turbulent.

• Similar to what is happening in the Similar to what is happening in the majority of the respiratory tract.majority of the respiratory tract.

Fig 6-21

Oxygen Therapy

Oxygen Equipment• If the alveolar oxygen is low (↓PIf the alveolar oxygen is low (↓PAAOO22), the arterial ), the arterial

oxygen (Poxygen (PaaOO22) will also be reduced. ) will also be reduced.

• The goal is to increase the alveolar oxygen level The goal is to increase the alveolar oxygen level (P(PAAOO22)by providing supplemental oxygen to the )by providing supplemental oxygen to the patient.patient.

• Four Categories of Oxygen Delivery EquipmentFour Categories of Oxygen Delivery Equipment– Low Flow *Low Flow *– ReservoirsReservoirs– EnclosuresEnclosures– High Flow *High Flow *

Estimating Patient Flow Needs

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

OROR

Rate Flow yInspiratorV

Rate Flow yInspiratorEIV

E

E

3

)(

Rate Flow yInspiratort

V

I

t 60

Example: Patient Flow Needs

Minute Ventilation = Minute Ventilation = 8 L/min8 L/min

Tidal Volume = 0.4 LTidal Volume = 0.4 L

Respiratory Rate = 20 Respiratory Rate = 20 bpmbpm

Insp. Time = 1 secInsp. Time = 1 sec

Low Flow Oxygen Delivery Systems

• Devices:Devices:– Nasal CannulaNasal Cannula– Nasal CatheterNasal Catheter– Transtracheal Transtracheal

Catheter Catheter (SCOOP)(SCOOP)

Low Flow Systems and Inspiratory Flow

• Device does not meet patient entire Device does not meet patient entire inspiratory flow needs.inspiratory flow needs.– Patient’s needs to draw in additional gas.Patient’s needs to draw in additional gas.– HAS NOTHING TO DO WITH THE HAS NOTHING TO DO WITH THE

FLOWMETER SETTING!FLOWMETER SETTING!– Provides low oxygen concentrations (22-45%).Provides low oxygen concentrations (22-45%).

• Some people include “Reservoir Systems” Some people include “Reservoir Systems” in this category as well.in this category as well.– Simple masks, Partial rebreathers, Non-Simple masks, Partial rebreathers, Non-

rebreathers, Reservoir cannulasrebreathers, Reservoir cannulas

Flow Needs

• Adults typically have an inspiratory flow Adults typically have an inspiratory flow of 24 - 30 L/min.of 24 - 30 L/min.

• Low flow devices provide ¼ – 8 L/min. of Low flow devices provide ¼ – 8 L/min. of 100% O100% O22..

• Flow difference must come from room air Flow difference must come from room air (21%) or reservoir (>21%).(21%) or reservoir (>21%).

Oxygen Concentration

• Low flow devices have air & oxygen mixing at Low flow devices have air & oxygen mixing at the patient’s airway.the patient’s airway.

• OO22 concentration is variable concentration is variable and depends on and depends on

the patient’s respiratory pattern.the patient’s respiratory pattern.– A higher OA higher O22 concentration is achieved when concentration is achieved when

breathing is at a slower rate and a slow flow. breathing is at a slower rate and a slow flow. • Less room air is brought into the system.Less room air is brought into the system.

– A lower OA lower O22 concentration is achieved when concentration is achieved when

breathing is at a higher rate & rapid flow.breathing is at a higher rate & rapid flow.

Oxygen Delivery Devices

High-Flow SystemsHigh-Flow Systems

FIO2 vs. FDO2

• The “D” stands for delivered.The “D” stands for delivered.

• Technically speaking, oxygen devices Technically speaking, oxygen devices “deliver” a specific amount of oxygen. “deliver” a specific amount of oxygen.

• What is actually “inspired” is related to What is actually “inspired” is related to how much air is entrained and dilutes the how much air is entrained and dilutes the oxygen flow.oxygen flow.

• Like…who cares?Like…who cares?

High Flow Oxygen Delivery Systems

• Devices:Devices:– Air-entrainment mask (venturi) *Air-entrainment mask (venturi) *– Air-entrainment nebulizer *Air-entrainment nebulizer *

• Aerosol MaskAerosol Mask• Tracheostomy CollarTracheostomy Collar• T-BarT-Bar• Face TentFace Tent

– BlenderBlender– Dual FlowmetersDual Flowmeters

Air Entrainment Nebulizer• Oxygen sourceOxygen source• Flow meterFlow meter• Nebulizer with sterile waterNebulizer with sterile water• Large bore tubingLarge bore tubing• Drain bagDrain bag• Patient interfacePatient interface

– Aerosol maskAerosol mask

– Trach collarTrach collar

– Face tentFace tent

– T-bar)T-bar)

Fluid Entrainment• Air entrainment masks & nebulizers use Air entrainment masks & nebulizers use

a method of fluid mixing known as fluid a method of fluid mixing known as fluid entrainment.entrainment.

• First fluid flow determines the amount of First fluid flow determines the amount of a second fluid that will be drawn into the a second fluid that will be drawn into the first fluid flow.first fluid flow. 100% O2 21%Air

Methods of Fluid Entrainment

• Jet mixing principleJet mixing principle– Air entrainment maskAir entrainment mask

• Bernoulli principleBernoulli principle– Air entrainment nebulizersAir entrainment nebulizers

• Both principles for fluid entrainment use the Both principles for fluid entrainment use the concept of: concept of:

– Decreasing cross sectional area Decreasing cross sectional area

– Increasing velocity of gasIncreasing velocity of gas

Law of Continuity

Jet Mixing Principle• The net effect is an increase in total flow.The net effect is an increase in total flow.

• This can result in a very precise amount This can result in a very precise amount of oxygen and air mixing.of oxygen and air mixing.

Source Gas (Oxygen)

Fig 38-13

Page 882

Factors Affecting Air Entrainment

• The amount of air that is entrained is The amount of air that is entrained is dependent on two factors:dependent on two factors:– Size of the jet orificeSize of the jet orifice– Size of the entrainment portsSize of the entrainment ports

• Air-entrainment masks work by altering Air-entrainment masks work by altering one of these factors.one of these factors.

Jet Orifice Size• Smaller jet opening causes increased velocity Smaller jet opening causes increased velocity

of main gas causing more entrainment of air.of main gas causing more entrainment of air.

• FFIIOO22 decreases decreases

• Total gas flow increasesTotal gas flow increases

Size of Entrainment Ports

• Larger ports allow more air to be entrainedLarger ports allow more air to be entrained

• FFIIOO22 decreases decreases

• Total flow increasesTotal flow increases

Air:Oxygen MixingSet O2%Set O2% Air:O2 ratioAir:O2 ratio

Liters of air mixing with 1 liter of 100% O2Liters of air mixing with 1 liter of 100% O2

Total flowTotal flow

100100 0:10:1 11

8080 0.3:10.3:1 1.31.3

7070 0.6:10.6:1 1.61.6

6060 1:11:1 22

5050 1.7:11.7:1 2.72.7

4040 3:13:1 44

3535 5:15:1 66

3030 8:18:1 99

2121 25:125:1 2626

Altering FIO2

• Oxygen flow remains constant and is set Oxygen flow remains constant and is set by RCP with a flow meter.by RCP with a flow meter.

• Air flow changes based on: Air flow changes based on: – Jet sizeJet size– Port sizePort size

• More air dilutes oxygen flow and More air dilutes oxygen flow and decreases Fdecreases FIIOO22..

What will happen to FIO2

when…

• I decrease the size of the jet? ____________I decrease the size of the jet? ____________• I increase the size of the jets? ___________I increase the size of the jets? ___________• I decrease the size of the ports? __________I decrease the size of the ports? __________• I increase the size of the ports? ___________I increase the size of the ports? ___________• I decrease the oxygen flow? _____________I decrease the oxygen flow? _____________• I increase the oxygen flow? ______________I increase the oxygen flow? ______________• I pinch the aerosol hose? _______________ I pinch the aerosol hose? _______________

(Back pressure against air entrainment)(Back pressure against air entrainment)

Bernoulli Effect• Fluids have three types of energy:Fluids have three types of energy:

– Potential Energy (the driving pressure)Potential Energy (the driving pressure)– Kinetic Energy (the energy created by a mass Kinetic Energy (the energy created by a mass

of fluid moving at a specific velocity)of fluid moving at a specific velocity)• Because the mass is never changing, it is directly Because the mass is never changing, it is directly

proportional to the velocity of the fluid.proportional to the velocity of the fluid.

– Pressure Energy (the energy exerted on the Pressure Energy (the energy exerted on the walls of the tube)walls of the tube)• This radial pressure is also known as lateral wall This radial pressure is also known as lateral wall

pressure.pressure.

Bernoulli Effect• As fluid flows through a tube, the pressure As fluid flows through a tube, the pressure

within the tube decreases over the length. within the tube decreases over the length.

Fig 6-24

Page 115

1700 – 27 July 1782 1700 – 27 July 1782 1700 – 27 July 1782

1700 –1782

Bernoulli Effect• Fluid velocity increases as the fluid travels Fluid velocity increases as the fluid travels

through a constriction.through a constriction.

Bernoulli Effect

• According to the First Law of Thermodynamics, According to the First Law of Thermodynamics, energy cannot be lost.energy cannot be lost.

• If the forward velocity is increasing (kinetic If the forward velocity is increasing (kinetic energy goes up), and potential energy is energy goes up), and potential energy is unchanged (the tube is level), the pressure unchanged (the tube is level), the pressure energy (lateral wall pressure ) would have to energy (lateral wall pressure ) would have to be decreasing.be decreasing.

• The smaller the constriction, the higher the The smaller the constriction, the higher the velocity and lower the lateral wall pressure.velocity and lower the lateral wall pressure.

Bernoulli Effect

Fig 6-25

Page 115

Velocity increases,

Lateral wall pressure decreases.

Venturi Principle

• If gas flowing through a tube meets a If gas flowing through a tube meets a small enough constriction, the pressure small enough constriction, the pressure will drop to sub atmospheric and actually will drop to sub atmospheric and actually entrain a second gas (fluid).entrain a second gas (fluid).

10 -510

1746 - 1822

Venturi Masks• Venturi masks don’t work on the Venturi Venturi masks don’t work on the Venturi

principle; they work on jet mixing.principle; they work on jet mixing.

Nebulizer Function

1. Based on Bernoulli & Venturi principles1. Based on Bernoulli & Venturi principles– Main gas flow (usually oxygen) Main gas flow (usually oxygen) – Entrains liquid to create aerosol particlesEntrains liquid to create aerosol particles

2. Based on jet mixing principle2. Based on jet mixing principle– Main gas flow (usually oxygen) Main gas flow (usually oxygen)

– Entrains air which lowers the FEntrains air which lowers the FIIOO22

Air:Oxygen Mixing

Set O2%Set O2% Air:O2 ratioAir:O2 ratioLiters of air mixing with 1 liter of 100% O2Liters of air mixing with 1 liter of 100% O2

Total flowTotal flow

100100 0:10:1 11

8080 0.3:10.3:1 1.31.3

7070 0.6:10.6:1 1.61.6

6060 1:11:1 22

5050 1.7:11.7:1 2.72.7

4040 3:13:1 44

3535 5:15:1 66

3030 8:18:1 99

2121 25:125:1 2626

Air:O2 Ratio example

• 40% O40% O22 has an Air:O has an Air:O22 ratio of 3:1 ratio of 3:1

• Oxygen flow Oxygen flow 1L/min1L/min = Air entrained 3 = Air entrained 3 Liters/minLiters/min– Total flow 4 L/minTotal flow 4 L/min

• OO22 flow meter flow meter 10 L/min10 L/min = Air entrained 30 = Air entrained 30

L/minL/min– Total flow 40 L/minTotal flow 40 L/min

Calculating the Air:O2 Ratio

FFIIOO22 of 35%: of 35%:

Air:OAir:O22 ratio = 4.6:1 or approximately 5:1 ratio = 4.6:1 or approximately 5:1

21

100

2

2

FIO

FIOoxygenair :

6414

65

2135

35100

21

100

2

2 .:

FIO

FIOoxygenair

Calculating the Air:O2 Ratio• The Magic BoxThe Magic Box

Calculating Device Flow

What is the air:O2 ratio for an air entrainment mask at FIO2 40%? What is the air:O2 ratio for an air entrainment mask at FIO2 40%?

• Ratio for 40% is 3:1Ratio for 40% is 3:1

If the OIf the O22 Flowmeter Flowmeter is set at 8 L/min is set at 8 L/min

Then the entrained airThen the entrained air will be 8x3 = 24 L/min will be 8x3 = 24 L/min

Total flow = (air + OTotal flow = (air + O22) = (8 + 24) = ) = (8 + 24) = 32 L/min 32 L/min

2319

60

2140

40100

21

100

2

2 .:

FIO

FIOoxygenair

Practice

• Sibberson’s Practical Math For RC:Sibberson’s Practical Math For RC:– Ch 4: Device Flow Rate, Sample Problems Ch 4: Device Flow Rate, Sample Problems

Third Set, pgs. 49-53.Third Set, pgs. 49-53.• Practice problems, pgs 54-55Practice problems, pgs 54-55

Is the Device Flow Adequate?

• Can the device be classified as a “high Can the device be classified as a “high flow” system?flow” system?– Will it meet or exceed the patient’s Will it meet or exceed the patient’s

inspiratory flow?inspiratory flow?

– Will the FWill the FIIOO22 be stable? be stable?

– Will the patient pull in room air and lower the Will the patient pull in room air and lower the FFIIOO22??

Peak Inspiratory Flow

• Peak Inspiratory flow (PIF)Peak Inspiratory flow (PIF)– The fastest speed at which the patient draws The fastest speed at which the patient draws

gas into the respiratory tract during gas into the respiratory tract during inspiration.inspiration.

– Normal adult PIF is 24 – 30 L/min.Normal adult PIF is 24 – 30 L/min.– Can be as high as 60 – 100 L/min.Can be as high as 60 – 100 L/min.

• Device flow must meet or exceed PIF to Device flow must meet or exceed PIF to be considered a “high flow” device.be considered a “high flow” device.

Estimating Patient Flow Needs

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

OROR

Rate Flow yInspiratorV

Rate Flow yInspiratorEIV

E

E

3

)(

Rate Flow yInspiratort

V

I

t 60

Which calculation to use?

• Choose your calculation based on the Choose your calculation based on the information given.information given.

• Example:Example:– Given information is VGiven information is Vtt .5L (500 mL) and rate 12 .5L (500 mL) and rate 12

– Which formula ___________________________Which formula ___________________________

• Example:Example:– Given information is VGiven information is Vtt .5L and t .5L and tII is 0.9 sec is 0.9 sec

– Which formula? __________________________Which formula? __________________________

Example: Patient Flow Needs

Minute Ventilation = Minute Ventilation = 8 L/min8 L/min

Tidal Volume = 0.4 LTidal Volume = 0.4 L

Respiratory Rate = 20 Respiratory Rate = 20 bpmbpm

Insp. Time = 1 secInsp. Time = 1 sec

Is the device flow adequate?

• Device flow was 32 L/minDevice flow was 32 L/min• Patient needs 24 L/minPatient needs 24 L/min• Device > patientDevice > patient = set F = set FIIOO22 delivered delivered

– FFDDOO2 2 = F= FIIOO22

• Device flow < patient flowDevice flow < patient flow = lower F = lower FIIOO22 then set deliveredthen set delivered– FFDDOO2 2 ≠ F≠ FIIOO22

ExampleO2

Flowmeter

Nebulizer

Aerosol tubing

Drain bagMask

Device flow

Inspiratory flowDevice flow should meet or exceed inspiratory flow

Air entrained

H20

entrained

(O2 & mist)

Will patient receive set FIO2?

• Patient flow:Patient flow:– Tidal volume .5LTidal volume .5L– Rate (f) 20Rate (f) 20– Insp. time 1 sec.Insp. time 1 sec.– I:E = 1:2I:E = 1:2

– Min.Vent. = VMin.Vent. = Vtt x f = __ x f = __

– Patient insp. FlowPatient insp. Flow = ____ = ____

• Device flow:Device flow:– FFIIOO22 60% 60%

– OO22 flow 8 L flow 8 L

– Air:OAir:O22 ratio ______ ratio ______

– Total flow _______Total flow _______

Will patient receive set FIO2?NO.

Gas Mixing Using Two Flowmeters

• Sometimes is may be necessary to Sometimes is may be necessary to blend oxygen and air together to obtain blend oxygen and air together to obtain a desirable Fa desirable FDDOO22. .

• The formula is:The formula is:

Flow Total

Rate) Flow Air(.2Rate Flow OxygenFDO

2

Gas Mixing Using Two Flowmeters

• Example: If an air flowmeter is set at 6 Example: If an air flowmeter is set at 6 L/min and the oxygen flowmeter is set L/min and the oxygen flowmeter is set at 2 L/min, calculate the Fat 2 L/min, calculate the FDDOO22..

Practice

• Sibberson’s Practical Math For RC:Sibberson’s Practical Math For RC:– Ch4: Inspiratory Flow Rates, Sample Ch4: Inspiratory Flow Rates, Sample

Problems First & Second Set, pgs. 47-49.Problems First & Second Set, pgs. 47-49.• Practice problems, pgs 53-54Practice problems, pgs 53-54

– Ch 12: I:E Ratio, Sample Problems Eighth Ch 12: I:E Ratio, Sample Problems Eighth Set, pgs 146-147Set, pgs 146-147• Practice Problems, pg. 156Practice Problems, pg. 156

Device flow vs. Patient flow

• Sibberson’s Practical Math For RC:Sibberson’s Practical Math For RC:– Ch4: Patient & Device Flow Comparison, Ch4: Patient & Device Flow Comparison,

Sample Problems Fourth Set, pgs. 51 - 52.Sample Problems Fourth Set, pgs. 51 - 52.• Practice problems, pgs 55 - 57Practice problems, pgs 55 - 57

ASSIGNMENTS

• Egan - Reading AssignmentsEgan - Reading Assignments– Ch 6: Fluid Dynamics, pgs. 112-117Ch 6: Fluid Dynamics, pgs. 112-117– Ch 38: Oxygen Delivery, pgs. 872-88Ch 38: Oxygen Delivery, pgs. 872-88– Ch 34: Mini Clinis, pgs. 882, 885, 887 & 888 Ch 34: Mini Clinis, pgs. 882, 885, 887 & 888 – 77

ASSIGNMENTS

• Sibberson’s Practical Math For RC:Sibberson’s Practical Math For RC:– Ch4: Inspiratory Flow Rates, Sample Ch4: Inspiratory Flow Rates, Sample

Problems First & Second Set, pgs. 47-49.Problems First & Second Set, pgs. 47-49.• Practice problems, pgs 53-54Practice problems, pgs 53-54

– Ch 12: I:E Ratio, Ch 12: I:E Ratio, Read OnlyRead Only pgs. 146-151 pgs. 146-151

ASSIGNMENTS

• Sibberson’s Practical Math For RC:Sibberson’s Practical Math For RC:– Ch 4: Device Flow Rate, Sample Problems Ch 4: Device Flow Rate, Sample Problems

Third Set, pgs. 49-53.Third Set, pgs. 49-53.• Practice problems, pgs 54-55Practice problems, pgs 54-55

– Ch 4: Device Flow vs. Patient Flow, Sample Ch 4: Device Flow vs. Patient Flow, Sample Problems Fourth Set, pgs. 51-52.Problems Fourth Set, pgs. 51-52.• Practice problems, pgs 55-57Practice problems, pgs 55-57