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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.
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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
P-V CURVE OF RESPIRATORY SYSTEM
Healthy lung - exercise
P
RV
FRV
ERV
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VTLC
TV
IRV
IC
P-V CURVE OF RESPIRATORY SYSTEM
Chronic obstructive airway disease- tidal breathing
PRV
EELV
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V
TLC
IC
EELV
IRV
P-V CURVE OF RESPIRATORY SYSTEM
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
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