AIRWAY PRESSURE RELEASE VENTILATION

APRVAhmed Al Gahtani, BSRC, RRT.

Associate Director Clinical Education & InstructorChairman, RTS Advisory Committee

Dept. of Respiratory Therapy ProgramInaya Medical College

SSRC Central & Northern Chapter Board Member for RC Education

APRV• What • When • How

What When How

What is APRV ■ Airway pressure release ventilation (APRV) was described more than

20 years ago by Stock & Down in 1987 as a CPAP with an intermittent release phase.

■ APRV is a time-cycled alternant between two levels of positive airway pressure, with the main time on the high level and a brief expiratory release to facilitate ventilation allows spontaneous breathing throughout the ventilation cycle

■ APRV applies CPAP (P high) for a prolonged time (T high) to maintain adequate lung volume & alveolar recruitment, with a time cycled release phase to a lower set of pressure (P low) for a short period of time (T low) or (release time) where most of the ventilation & CO2 removal occurs

■ The Dräger Evita was the first ventilator in the United States to provide APRV. Subsequently other intensive care unit (ICU) ventilators, such as the Hamilton G-5, the Puritan Bennett 840, the Dräger V500, the CareFusion AVEA, and the Maquet Servo-i, incorporated APRV.

■ Servo-i refers to APRV as Bi-vent ■ Puritan Bennett 840 uses the term Bi-level ■ Hamilton G5 refers to APRV as Duo-PAP. ■ The function of APRV may also be different with

each ventilator.■ ‘APRV’ is common to users in North America,

biphasic positive airway pressure (BIPAP) was introduced in Europe

What is APRV

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APRV Set Parameters

■P high. ■P low ■T high ■T low ■(10% to 30%)

HOW

When ■ APRV indicated for ARDS management and atelectasis after major

surgery.■ APRV presents many attractive benefits as an alternative mode of

mechanical ventilation in patients who do not respond to conventional modes.

■ APRV contraindicated with COPD & Asthma, Deep sedation, and NMD

■ This study is the largest reported randomized trial of APRV to date. Trauma patients at risk for ARDS ventilated with

■ APRV had similar outcomes as those treated with LOVT ■ APRV seems to be a safe alternative ventilator modality that provides

increased mean airway pressure as a potential recruitment mechanism.■ Sedation requirements seem to be similar to SIMV.■ Additional trials in patients with documented ARDS will be necessary for

further clarification of its ultimate utility.

■ The preemptive ventilation strategy presented in our study has the potential to change the current clinical practice paradigm from treating ARDS once it manifests to preventing it from ever developing.

■ Clinical application can begin without delay with an immediate impact on patient care.

■ If successful, our ventilation strategy would be the first prophylactic intervention of any kind to prevent ARDS.

PROS AND CONSAdvantages■ alveolar recruitment and improved

oxygenation■ preservation of spontaneous

breathing■ reduction of left ventricular

transmural pressure and therefore reduction of left ventricular afterload

■ potential lung-protective effect■ better ventilation of dependent areas■ lower sedation requirements to allow

spontaneous breathing

Disadvantages■ risks of volutrauma from increased

transpulmonary pressure■ increased work of breathing due to

spontaneous breathing■ increased energy expenditure due to

spontaneous breathing■ worsening of air leaks (bronchopleural

fistula)■ Increased right ventricular afterload,

worsening of pulmonary hypertension■ Reduction of right ventricular venous return:

may worsen intracranial hypertension, may worsen cardiac output in hypovolemia

■ Risk of dynamic hyperinflation

Four Hypotheses Are Possible1, APRV/BIPAP is better than A/C; 2, APRV/BIPAP is worse than A/C; 3,there is no difference between APRV/BIPAP and A/C; 4,it is undetermined whether there is a difference between APRV/BIPAP and A/C.

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Finally