Basic Pulmonary Mechanics during Mechanical Ventilation
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Transcript of Basic Pulmonary Mechanics during Mechanical Ventilation
Basic Pulmonary Mechanics during Mechanical Ventilation
Equation of Motion
dP = R x Flow + dV / C st
Points of Discussion1.Equation of motion2.Airway pressures3.Compliance4.Resistance5.Pressure-Time6.Flow-Time7.Pressure-volume loop8.Flow-volume loop
Precondition of Inspiration
• Pa < Pb– Spontaneous
breath• Pb > Pa
– Mechanical ventilation
Pb
Pa
Gas Flow
compliance = Dvolume / Dpressure
volume
transairwaypressure
transthoracicpressure
transrespiratorypressure
Lung Mechanics resistance = Dpressure / Dflowflow
Equation of MotionDYNAMIC 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
Components of Inflation Pressure
Begin Expiration
P aw (
cm H
2O)
Time (sec)
Begin Inspiration
PIP
Pplateau
(Palveolar)
Transairway Pressure (PTA)}
Expiration
Inspiratory Pause
Begin Inspiration Begin Expiration
P aw (
cm H
2O)
Time (sec)
Airway Resi
stance
Distending (Alveolar)
Pressure Expiration
Inflation Hold(seconds)
Begin Expiration
P aw (
cm H
2O)
Time (sec)Begin Inspiration
PIP
Pplateau
(Palveolar
Transairway Pressure (PTA)
}Exhalation Valve Opens
Expiration
PIP
Spontaneous vs. Mechanical
Mechanical
Time (sec)
SpontaneousPaw (cm H2O)
Inspiration
ExpirationExpiration
Inspiration
PIP vs Pplat
NormalHigh Raw
High FlowLow Compliance
Time (sec)
Paw
(cm
H2O
)PIP
PPlat
PIP
PIP PIP
PPlatPPlat
PPlat
Mean Airway Pressure
Increase FlowIncrease peak pressureLengthen Inspiratory TimeIncrease RateIncrease PEEP
Inspiratory Flow Pattern
Inspiration
Expiration
Time (sec)
Flow
(L/m
in)
Beginning of inspirationexhalation valve closes
Peak inspiratory flow ratePIFR
Beginning of expirationexhalation valve opens
Total cycle timeTCT
Inspiratory Time
TI
Expiratory Time TE
Peak Expiratory Flow Rate PEFR