Mechanical Ventilation PV
Curves
Techniques for Measurement
1. Supersyringe
2. Constant Flow
3. Multiple Occlusion
Low Constant Flow
• Simple• Can be performed on ventilator (some types)• Avoids disconnect• Hysteresis • Heavy sedation or paralysis required• Flow 9 L/min for “quasi-static” conditions1
1Qin Lu, AJRCCM 1999;159:275-282Servillo, AJRCCM 1997;155:1629-1636
Radford, Tissue Elasticity, 1957
Surface forces due to air-liquidinterface
Gattinoni, ARRD 1987;136:730-736
Pflex
P
"safe"window
zone of overdistension
V
Pressure-Volume Curve
LIP
UIPzone of derecruitment and atelectasis
PV CurveNormal ARDS COPD
PV Curve
Normal
PV Curve
ARDS
P
"safe"window
zone of overdistension
V
atelectrauma
volutrauma
Lung Protective Ventilator Strategies
LIP
UIPzone of derecruitment and atelectasis
DON’T EVEN
THINKOF PARKING
HERE
Pressure
Vo
lum
e
Safe
zon
e
Overdistention
Derecruited
Lower Pflex, LIP
Upper Pflex, UIP
PV Curve in ARDS
Preventing Overdistention and Under-Recruitment
Injury“Lung Protective” Ventilation“Lung Protective” Ventilation
VOLUME
VOLUME
PressurePressure
Limit Distending PressureLimit Distending Pressure
Add PEEPAdd PEEP
Limit VT
PV Curve
COPD