Transcript Flow Patterns - Middle East Critical Care Assembly

Basic Pulmonary Mechanics
during Mechanical Ventilation
Equation of Motion
dP = R x Flow + dV / C st
Points of Discussion
1. Equation of motion
2. Airway pressures
3. Compliance
4. Resistance
5. Pressure-Time
6. Flow-Time
7. Pressure-volume loop
8. Flow-volume loop
Spontaneous Breathing
Exhalation
Inspiration
Precondition of Inspiration
Pb
Gas Flow
• Pa < Pb
– Spontaneous
breath
• Pb > Pa
– Mechanical
ventilation
Pa
Lung Mechanics
resistance = Dpressure / Dflow
flow
transairway
pressure
transrespiratory
pressure
volume
transthoracic
pressure
compliance = Dvolume / Dpressure
Tube + Spring Model
Resistive Forces
Elastic Forces
Airway Resistance
“The Feature of the Tube”
R=
D P
D F
Pressure Difference = Flow Rate x Resistance
Compliance
D V
Cs = D P
Volume
DV
DP
Pressure
Pressure Difference = Volume Change / Compliance
Compliance and Resistance
DP
R=
DF
D V
Cs=
D P
Equation of Motion
DYNAMIC CHARACTERISTICS:
dP = dV / Cdyn
RESISTANCE:
dPresistive = R x Flow
STATIC COMPLIANCE:
dPdistensive = dV / Cst
dP = dPresist. + dP dist.
dP = R x Flow + dV / C st
Equation of Motion
dP = R x Flow + dV / C st
Paw (cm H2O)
Components of Inflation Pressure
PIP
}
Pplateau
(Palveolar)
Transairway Pressure (PTA)
Inspiratory Pause
Expiration
Time (sec)
Begin Inspiration
Begin Expiration
Paw (cm H2O)
PIP
Pplateau
Pressure
} Transairway
(P )
TA
Exhalation Valve Opens
(Palveolar
Expiration
Time (sec)
Begin Expiration
Begin Inspiration
Paw (cm H2O)
PIP
Inflation Hold
(seconds)
Distending
(Alveolar)
Pressure
Expiration
Time (sec)
Begin Inspiration
Begin Expiration
Spontaneous vs. Mechanical
Mechanical
Inspiration
Paw
(cm H2O)
Spontaneous
Expiration
Inspiration
Expiration
Time (sec)
PIP vs
Pplat
PIP
Paw (cm H2O)
PIP
PPlat
PPlat
High Raw
Normal
PIP
PIP
High Flow
PPlat
Low Compliance
PPlat
Time (sec)
Mean Airway Pressure
Lengthen
Increase
Increase
Increase
Increase
Inspiratory
peak
PEEP
Rate
pressure
FlowTime
Inspiratory Flow Pattern
Peak inspiratory flow rate
PIFR
Beginning of expiration
exhalation valve opens
Flow (L/min)
Inspiration
Inspiratory
Time
TI
Expiratory Time
TE
Time (sec)
Beginning of inspiration
exhalation valve closes
Expiration
Total cycle time
TCT
Peak Expiratory Flow Rate PEFR
Flow vs Time
Flow (L/min)
Inspiration
Time (sec)
Expiration
Flow Patterns
SQUARE
ACCELERATING
DECELERATING
SINE
Flow Patterns and Effects of
Volume
SQUARE
DECELERATING
ACCELERATING
SINE
Mechanical vs Spontaneous
Mechanical
Spontaneous
Inspiration
Expiration
Volume vs. Time
Volume (ml)
Inspiratory Tidal Volume
Inspiration
Expiration
TI
Time (sec)
FRC and PV Loop
Normal Compliance
VOLUME
TLC
FRC
0
Negative
Positive
DISTENDING PRESSURE
FRC
Components of Pressure-Volume
Loop
VT
Volume
(mL)
Paw (cm H2O)
PIP
PEEP and P-V Loop
VT
Volume
(mL)
PEEP
Paw (cm H2O)
PIP
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