1. Then What Is APRV?
• APRV - a form of BiLevel but utilizes a very short
expiratory time for pressure release
Airway Pressure Release • APRV always implies a severe inverse I:E ratio
Ventilation • All spontaneous breathing is done at upper pressure
level
† Synchronized Transition
FULL TIDAL VOLUME * Spontaneous Breaths
* * * *† * * *
VENTILATION † † PEEPHI
P
PEEPLO
T
Bottom Line Where do we ventilate patients?
• Conventional
strategies –
• The patient does not need to be paralysed inflate along Vol
or deeply sedated to be placed on inverse lower limb of
V/P curve
ratio ventilation, with severe hypoxia
• Modern
• Earlier weaning Strategies use
• Preservation of respiratory muscle reserve the expiratory
limb
Pressure

2. APRV Clinical Application
Guidelines
• Starting frequency commonly 6 - 10 breaths / min
• Time at upper pressure not important
• Time at lower pressure should be short enough so as not to allow
complete exhalation - typically ~ 0.8 seconds
Does APRV
PCIRC 40
0.8 sec
30
cmH2O
20
10
0
Make a difference?
10
-20
0 2 4 6 8 10 12s
INSP 80
60
40
. 20
V
0
L 20
min
40
60
EXP -80
Three-dimensional reconstructions of the chest Spontaneous breathing during APRV
wall and atelectatic regions in the dependent part
improves lung areation in OA induced ALI
of the lungs in an anaesthetized patient
Hedenstierna G. Clinical Physiology and Functional Imaging 23 (3), 123-129.
Wrigge et al. Anesthesiology 2003; 99:376-84

3. APRV & Spontaneous Long-term effects of spontaneous
Breathing breathing during MV in ARDS
• 24 patients with severe ARDS • 30 patients with ARDS following major
trauma
• APRV with Spontaneous breathing vs PSV
– Reduced shunt • 15 managed with PCV (+NMB)
– Reduced dead space – weaned with APRV
– Improved V/Q matching • 15 managed with APRV and spont. breath
Purensen C, AJCCM 159:1999 Putensen AJRCCM 164: 2001
Long-term effects of spontaneous Long-term effects of spontaneous
breathing during MV in ARDS breathing during MV in ARDS
• Primary use of APRV was
associated with:
• Increases
– In respiratory system
compliance
– In arterial oxygen tension
(PaO2)
– In cardiac index (CI)
– In oxygen delivery (DO=)
• Reductions in
– Venous admixture (QVA/QT)
– Oxygen extraction
Putensen AJRCCM 164: 2001
Putensen AJRCCM 164: 2001