aprv

APRV (BiLevel Mode)

Nikki Henry, Respiratory Therapy2011

Is my patient in ARDS?

Divide the PaO2/FiO2

400-500 Normal<300 ALI (Acute Lung Injury) –

impending ARDS<200 ARDS

IndicationsPEEP > 10 and FiO2 > 60% (Shunting)

PaO2/FiO2 < 300

Bilateral infiltrates

No evidence of left atrial hypertension

TerminologyP High – the upper CPAP level. Analogous

to MAP (mean airway pressure) and thus affects oxygenation

P Low – is the lower pressure setting.

T High- is the inspiratory time phase for the high CPAP level (P High).

T PEEP or T low- is the release time allowing CO2 elimination

Setting up APRVPress the vent set-up key on the

lower screen

Select Bilevel for mode – this will automatically set up the vent for PC (mandatory type)

Press continue

Frequency

Set frequency at 6-8 (max 10)

This is the release rate when the vent will change from Phigh to Plow

Total rate for patient should be 18-38

Initial Settings - PHighSet the Phigh to the plateau

pressure from previous VC/PC mode

P High – Set a plateau pressure typically about 20-25 cm H2O.

In patients with Pplateau at or above 30 cm H2O, set at 30 cm H2O

PEEP LowSet PEEP at zero cm H2O.

This provides a rapid drop in pressure, and a maximum DP for unimpeded expiratory gas flow.

Avoid lung collapse during Tlow.

Rapid pressure drops allow for quick resumption of Phigh (recruitment)

TLowOnce in the time bar screen you will see

three padlocks

Press on the padlock to the far right. This will hold Tlow constant.

Set Tlow at 0.4-1.0 sec

Make sure the Tlow value is displayed on the set parameters section (blue boxes above the time bar)

Patient should NOT take any spontaneous breaths on Tlow – if they do then the Tlow is too high!

Goal of TLowThe goal of termination of Tlow is

between 50-75% of Peak Expiratory Flow Rate (PEFR)

THigh Once Tlow is locked any change in frequency will

result in a change in Thigh

To adjust Thigh change frequency first

Pressure Support on APRV

State with Tube Compensation. If the spontaneous Vt are low switch to PS

PS at Phigh = (Plow + PS) – Phigh

Managing a patient on APRV

How to optimize PHigh at FiO2 > or = 60%

How to manage CO2

Weaning From APRV1. FiO2 SHOULD BE WEANED FIRST.

(Target < 50% with SpO2 appropriate.)

2. Reducing P High, by 2 cmH20 increments until the P High is below 20 cmH2O.

3. Increasing T High to change vent set rate by 5 releases/minute

“Drop and Stretch” WeaningWhen ready to wean – Phigh

is dropped and the frequency is dropped in small increments. THigh will be stretched out sequentially. This is called the Drop and Stretch Method.

“Drop and Stretch”

This is continued if the patient is spontaneously breathing and until the PHigh is 10-15 cmH2O and the THigh is 10-15 seconds.

At this point, the patient is effectively on CPAP.

During WeaningAdd Pressure Support judiciously.

Add Pressure Support to P High in order to decrease WOB while avoiding over-distention,

P High + PS < 30 cmH2O.