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