expiratory flow limitation disease

7/30/2019 expiratory flow limitation disease

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(;3,5$725


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COPD is a disease of resistance during expiration

but

with the consequence of restriction during inspiration.

Ubaidur Rahaman, Senior Resident, CCM, SGPGIMS, Lucknow, India


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Pressure Volume relationshipof

respiratory system



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75

100

Chest wall Lung

Chest wall and Lung( respiratory system)

acity%

TLC

P-V curve of Lung, Chest wall and Respiratory system

0

25

50

0-20 20

FRC

RV

Pressure ( cm H2O)Ppl, Pcw, Prs

Vitalca



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Resting Volume of Respiratory system

At End Expiration

Elastic force of LUNG Elastic force of CHEST WALL=

Functional Residual Capacity(FRC)



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5.0

3.0

IRVIC

VCTV

LUNG VOLUMES

0

2.5

1.25

RV

ERV

FRC



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Pressure, Volume and Flow

relationship

of Respiratory system



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Relationship between intrathoracic pressures

TPP = PA Ppl

TPP = Transpulmonary PressurePA = Alveolar PressurePpl = Pleural PressurePel = lung elastic recoil pressure

PA = Ppl + Pel

TPP = (Ppl + Pel) (Ppl) = Pel



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Relationship between intrathoracic pressures

=

TAP = Transairway Pressure

Paw = airway pressurePpl = Pleural Pressure

TPP

TAP Paw



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-5 -5

0

End expiration

PA = 0

TPP = PA Ppl

0

-5-5

Ppl = -5

TPP = 0 (-5) = +5



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-7 -7

0

Beginning of inspiration

TPP = PA Ppl

Ppl = -7

-2

-7-7

= A -

PA= +5 7 = -2



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-7 -7

0

Mid inspiration

-1

-7-7



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-5 -5

0

Beginning of passive expiration

TPP = PA Ppl

Ppl = -5

+2

-5-5

= A -

PA= +2



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-5 -5

0

Mid expiration

TPP = PA Ppl

PA = +1

+1

-5-5

= -

PA= +6



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TPP and TAP remains positiveTPP and TAP remains positive

Throughout the respiratory cycleThroughout the respiratory cycle

In healthy lung during normal tidal respirationIn healthy lung during normal tidal respiration

keeping the alveoli and airwayskeeping the alveoli and airwayspatentpatent



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+10 +10

0

Beginning of forced expiration

TPP = PA Ppl

Ppl = +10

+10

+8

+6

+4

+2

+17

+10+10

+7 = PA (+10))

PA= +17+15

+13



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+10 +10

0

forced expiration

+10

+8

+6

+4

+2

TAP = Paw Pp

TAP = (+10) ( +10) = 0

+17

+10 +10

+15

+13

Dynamic airway Collapse ( DAC)

Expiratory Flow Limitation

Equal Pressure Point ( EPP)



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Equal Pressure Point ( EPP)Point in airway where TAP is zero during expiration

Dynamic Airway Collapse

Point in airway distal to EPP, TAP becomes negative,causing airway to collapse

No amount of effort will increase the expiratory flow

Expiratory Flow limitation



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First 11 generation of airway ( bronchi)supported by cartilage ring/ plates

Counter balance of Dynamic Airway Collapse

12th generation and beyond ( bronchioles)supported by tethering effect of elastic recoil of surrounding lung parenchyma

cartilagenous support in bronchi

Lung volume in bronchioles

Patency of airways is a function of



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Equal Pressure Point

Dynamic point

As airway resistance increasesor

Lung volume decreasesMoves closer to Alveoli



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+10 +10

0

+10

+8

+6

+4

+2

+2

+4

+6

+10 +10

0

FORCED EXPIRATION

+17

+10 +10

+15

+13

Beginning of forced expiration

+10 +10

+12

+10

Mid forced expiration



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Airway disease

COPD, Asthma

Destruction of cartilage of airway

can be a manifestation of

Expiratory Flow Limitation

Lung parenchyma disease

leading to reduced lung volume

collapse, lung destruction, pneumonectomy



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There is no dynamic airway collapse

No expiratory flow limitation

IN HEALTHY LUNG

During quiet breathing

Because of invagination of posterior membrane of tracheo bronchial tree

During forced expiration

Small degree of dynamic airway collapse can occur

(Upto 40% reduction in cross sectional area of airway)



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Dynamic airway collapse during Coughing



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Flow and Time Relationship

OfRespiratory system



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Concept of



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Effect of gravity

+

weight of lung

Vertical gradientin

Ppl and TTP

Dependent alveoli have lesser volumethan non dependent alveoli



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PLEURAL PRESSURE AND TPP GRADIENT(At FRC)

BODY

POSITION

TOP OF

LUNG

BOTTOM OF

LUNG

Ppl TPP Ppl TPP

UPRIGHT -8 8 -2 2

SUPINE -4 4 0 0

PRONE -3.5 3.5 0 0



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P- V curve of Respiratory system at different Lung volumesVERTICAL GRANIDIENT

FRC



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TLC

P- V curve of Respiratory system at different Lung volumesVERTICAL GRANIDIENT

RV



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IN HEALTHY LUNG

During forced expiration

Dynamic airway collapse occursstarting from dependent lung regions

Critical volume of lung during expiration to prevent dynamic airway collapseCLOSING CAPACITY



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5.0

3.0

CLOSING CAPACITY

TLC

In healthy lung44 years

CC= FRC in supine position

66 yearsCC = FRC in upright position

CC

0

2.5

1.25RV

CC

FRC

Smoking, ageing, obesity,supine positionIncreases CC



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5.0

3.0

Effect of PEEP on CLOSING CAPACITY

CC

TLC

PEEP

0

2.5

1.25RV

FRC



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TIME CONSTANT

length of time required to fill or empty lung unitslength of time required to fill or empty lung units

Alveoli = compliance

Function of

Airway= resistance

TC = C R

1 TC = 63% of lung unit fill/ empty3 TC = 95% 5 TC = 99%



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normal

Decreased compliance

Increased resistance

TC

TC



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O structive Airway Disease



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Increased Airway Resistance

dynamic airway collapsedynamic airway collapse

Expiratory Flow LimitationExpiratory Flow Limitation

DYNAMIC HYPERINFLATION(DHI)

Increased End Expiratory Lung Volume ( EELV)

Air TrappingAir Trapping



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v

T

FRC

DHI is probably an adaptive response to overcome DAC



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V

TLC

IRV

IC

P-V CURVE OF RESPIRATORY SYSTEM

Healthy lung- tidal ventilation

P

RV

FRC

ERV



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V

TLC

IRV

IC


Healthy lung - exercise

P

RV

FRV

ERV



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VTLC

TV

IRV

IC


Chronic obstructive airway disease- tidal breathing

PRV

EELV



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V

TLC

IC

EELV

IRV


Chronic obstructive airway disease- exacerbation

PRV

EELV



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Increased EELVIncreased EELV

More Zone I and II formationMore Zone I and II formation

Increased dead spaceIncreased dead space

EFFECT ON GAS EXCHANGE

V/Q mismatch

Increased minute ventilation requirement



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Displacement of respiratory system towards upper flatter portion of PDisplacement of respiratory system towards upper flatter portion of P--V curveV curve

Altered geometry of the chest wallAltered geometry of the chest wall

Flattened and lowered diaphragm, more horizontal rib cageFlattened and lowered diaphragm, more horizontal rib cage

EFFECT ON DYNAMIC MECHANICS

Respiratory muscles operating at higher lung volumesRespiratory muscles operating at higher lung volumes

Increased elastic loading of inspiratory muscles at end expirationIncreased elastic loading of inspiratory muscles at end expiration



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EFFECT ON DYNAMIC MECHANICS

Before starting inspiratory flow must overcome this increased elastic loadBefore starting inspiratory flow must overcome this increased elastic load

Effort required to generate tidal volume is more than the muscle canEffort required to generate tidal volume is more than the muscle can

generate at that lung volumegenerate at that lung volume

xp ratory musc es ax s o contract on s a terexp ratory musc es ax s o contract on s a tere

paradoxical indrawing of lower ribsparadoxical indrawing of lower ribs hoover signhoover sign

Decreased ventilatory capacityFunctional muscle weakness and fatigue

Increased WOB



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Increased EELVIncreased EELV

Increased TPPIncreased TPP

preload andpreload and afterload of RVafterload of RV

Increased ventilatory driveIncreased ventilatory drive

More negative pleural pressureMore negative pleural pressure

RV preload in face ofRV preload in face of RV afterloadRV afterload

EFFECT ON HEMODYNAMICS

Series ventriclular interdependenceSeries ventriclular interdependence

LV stroke volume

Hypotension

Parallel ventricular interdependence

LV filing compromised

LV dysfunction and failure



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IncreasedIncreasedventilatory driveventilatory drive

EFFECT ON PATIENT

anxietyanxiety

WorseningWorseninghemodynamicshemodynamics

IncreasedIncreasedWOBWOB

NeuromechanicalNeuromechanicaldiscouplingdiscoupling

VQ mismatchVQ mismatch

dyspnoea

Neural drive= Increased RR = decreased expiratory timeNeural drive= Increased RR = decreased expiratory time

Expiratory flow limitation = need for increased expiratory timeExpiratory flow limitation = need for increased expiratory time



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+4 +4

0

+2

+2+4 +4

0

forced expiration( obstructive airway disease)

+5

+4

+3

+6

+4+4

+5

+4

+6

+4+4

Pursed lip breathingPEEP



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MANAGEMENTGOAL



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CORRECTION OF GAS EXCHANGEREDUCTION OF WOB

CORRECTION OFLUNG MECHANICS

TREATMENT OF BASELINE DISEASE



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Prevention of DHI

CORRECTION OF LUNG MECHANICS

PPVPEEP

Easy Inspiratory flowTreatment of disease Prevention of DAC

Neuro muscular recouplingsedation,anti anxiety

PPVAdequate expiratory time



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Positive Pressure Ventilation



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PEEPFor easy inspiration

o +7

+10 +10

-11 -4



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-7 -7

0

Beginning of inspiration

TPP = PA Ppl

Ppl = -7

+10

-7-7

= A -

PA= +5 7 = -2



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+4 +4

PEEPFor easy expiration

+5

+4

+3

+6

+4+4

PEEP



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Setting total cycle timeSetting total cycle time

Flow riseFlow risecyc ngcyc ng

Calculation of expiratory timeCalculation of expiratory timeCalculation of TCTCalculation of TCT



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the difficulty lies, not in new ideas,

but escaping old ones,

which ramify, for those brought up with them,

as most of us have been, into every corner of our minds.

- John Maynard Keynes

Thank you

expiratory flow limitation disease

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