Mechanical Ventilation: Airway Pressure Release Ventilation (Respiratory Therapy)

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ALERT

Airway pressure release ventilation (APRV) is not recommended in patients who have deep or heavy sedation or obstructive lung conditions that require longer expiratory time.

Neuromuscular blockade should not be used with APRV that requires spontaneous breathing to meet the patient’s ventilatory needs.

OVERVIEW

APRV uses pressure-controlled, time-triggered, and time-cycled settings with inverse inspiratory-to-expiratory (I:E) ratios that allow unrestricted spontaneous breathing with or without pressure support (PS).^{undefined#ref2">2} Similar modes, like BiVent^™, Bilevel^™ and DuoPAP^™, have brand-specific terminology and settings.² APRV recruits dependent lung regions without increasing airway pressure, making it a lung-protective strategy for managing acute respiratory distress syndrome (ARDS), pneumonia, and atelectasis by maximizing alveolar recruitment while minimizing pressure-related lung injury. There is limited consensus on initial settings, so a time-controlled adaptive ventilation (TCAV) protocol should be considered when using APRV.¹

APRV applies a high continuous positive airway pressure (CPAP), called P high, for a prolonged time (T high) to promote alveolar recruitment and oxygenation. APRV adds a time-cycled release phase that drops to a lower set CPAP (P low) for a short period of time (T low) to allow ventilation and carbon dioxide removal (Figure 1). The difference between P high and P low determines the tidal volume (VT) delivered.⁶ The difference between P high and P low should be adjusted to deliver a VT of 6 to 8 mL/kg in accordance with ARDS Network protocol.⁵ PS should be set correctly for P high and P low according to the manufacturer’s instructions, as this can vary between ventilators.

Time settings include time high (T high) that is set for the length of time at P high, and time low (T low) that is set for the length of time at P low. These parameters are set to achieve inverse ratio ventilation (IRV), where inspiratory time is longer than expiratory time, increasing mean airway pressure (MAP) and optimizing gas exchange. Patients with obstructive lung disease may not tolerate APRV due to auto-positive end-expiratory pressure (PEEP) and IRV causing patient-ventilator asynchrony.^4,6

SUPPLIES

See Supplies tab at the top of the page.

EDUCATION

• Give developmentally and culturally appropriate education based on the desire for knowledge, readiness to learn, preferred learning style, and overall neurologic and psychosocial state.
• Explain the need for ventilator changes to the patient and family.
• Encourage questions and answer them as they arise.

ASSESSMENT AND PREPARATION

Assessment

1. Assess the patient for indications for APRV use and signs of ARDS.²
   1. Decreasing partial pressure of arterial oxygen/fraction of inspired oxygen (PaO₂/FIO₂) ratio
   2. Increasing plateau pressure, peak inspiratory pressure (PIP), or MAP
   3. Bilateral infiltrates on a chest radiograph
2. Assess the patient’s hemodynamic and cardiorespiratory systems.
3. Determine if the patient or family has health literacy needs or requires tools or assistance to effectively communicate. Be sure these needs can be met without compromising safety.
4. Review the patient’s and family’s previous experience and knowledge of mechanical ventilation and understanding of the care to be provided.

Preparation

1. Gather equipment, including a ventilator with APRV or equivalent mode, circuit, humidification device, filters (if needed), manual resuscitation bag, and closed-suction device.
2. Before initiating the mechanical ventilator, check the microprocessor or ventilation system. Perform a short self-test as appropriate.
   1. Verify compliance of the ventilator circuit with the humidification device and filters (if needed).
   2. Document the completed ventilation system test. Include pass or fail, date, initials or signature, and credentials.
3. Verify the authorized practitioner’s order for the initiation of mechanical ventilation or ventilation change.
4. Consider a TCAV protocol to guide ventilator settings and strategy when using APRV, whether the patient is newly intubated or being transitioned from conventional ventilation.

PROCEDURE

1. Clean hands and put on appropriate personal protective equipment (PPE) based on the risk of exposure to body fluids or infection precautions.
2. Verify the correct patient using two identifiers.
3. Explain the procedure and ensure that the patient agrees to treatment.
4. Transition the patient to APRV from conventional ventilation.

   Setting options, terminology, and abbreviations may be brand specific based on the trademarked mechanical ventilator specifications.⁶

   1. Set P high.
      1. Use the measured plateau pressure if transitioning from a volume-controlled mode as a starting point.^1,2
      2. Use the set inspiratory pressure if transitioning from a pressure-controlled mode as a starting point.^1,2

         P-high should not exceed 30 cm H₂O to minimize the risk of ventilator-induced lung injury.^2,6

   2. Set P low at 0 cm H₂O.^1,2

      Rationale: P low reduces resistance in expiratory gas flow during the quick pressure drop.²

   3. Set T high from 3 to 6 seconds and adjust according to the patient’s needs.^1,6

      Rationale: T high of less than 3 seconds may result in lower MAP that may not achieve optimal alveolar recruitment.⁶

      T high of greater than 6 seconds may cause carbon dioxide retention.⁶

   4. Set T low from 0.5 to 0.8 seconds as determined by the TCAV protocol including expiratory gas flow curve analysis.⁶

      T low should be short enough to prevent alveolar derecruitment and long enough for gas exchange.⁴

5. Set the patient sensitivity for flow-triggered or pressure-triggered spontaneous breaths.
6. Set PS as needed to increase spontaneous VT and verify P high and P low PS with the pressure-time waveform.
7. Set FIO₂ for the desired PaO₂ or peripheral oxygen saturation (SpO₂) level.
8. Adjust settings based on the patient’s release and spontaneous VT, SpO₂, end-tidal carbon dioxide (ETCO₂), arterial blood gas (ABG) values, expiratory gas flow pattern, and clinical status.
   1. To decrease partial pressure of carbon dioxide (PaCO₂):
      1. Decrease T high (less time at T high allows more PaCO₂ removal at T low).
      2. Increase P high in 2- to 3-cm H₂O increments to increase MAP and tidal volume.⁶

         Monitor VT and PIP, which should be below 30 cm H₂O.⁶

      3. Increase T low to allow more time for exhalation and PaCO₂ removal.

         Monitor oxygenation because increasing T low may cause alveolar derecruitment.²

   2. To increase PaCO₂:
      1. Increase T high (fewer releases per minute) in small increments.
      2. Decrease P high to decrease MAP, VT, and minute volume.

         Monitor oxygenation and avoid alveolar derecruitment.²

   3. To increase PaO₂:
      1. Increase FIO₂.
      2. Increase P high in 2-cm H₂O increments to increase MAP.⁶
      3. Increase T high slowly (in 0.5-second increments).⁶
      4. Use alveolar recruitment maneuvers.
      5. Consider decreasing T low in 0.1-second increments (this may reduce VT and affect PaCO₂).⁶
9. Evaluate the patient’s readiness for weaning.
   1. Wean FIO₂ to 40%.¹
   2. Simultaneously decrease P high and increase T high incrementally until transitioning to CPAP is possible.^2,6
      1. Decrease P high in 2- to 3-cm H₂O increments until it is less than or equal to 10 cm H₂O.²
      2. Increase T high in 0.5- to 2-second increments until it is approximately 12 to 15 seconds.²
      3. Changes should be incremental, and the time interval between each simultaneous P high and T high change is patient dependent.
   3. Transition to CPAP mode.
   4. Set pressure support as needed to increase spontaneous VT and support spontaneous breathing efforts.

      Rationale: Pressure support increases the volume in spontaneous breaths.

10. Ensure that all ventilator alarms are on and set appropriately for the patient’s individual ventilator settings.
11. Remove PPE and clean hands.
12. Document the procedure in the patient’s record.

MONITORING AND CARE

1. Regularly perform a check of ventilator settings, alarms, and measured parameters.
2. Monitor the patient’s ventilator pressure-time and flow-time waveforms to evaluate spontaneous and delivered pressure and inspiratory and expiratory flow patterns.
3. Maintain the humidification device and circuit temperature, if applicable to avoid excessive condensation in the ventilator circuit.
4. Assess the patient’s overall level of comfort and patient-ventilator synchrony.
5. To minimize alveolar derecruitment, consider using a closed suction device to minimize the number of times the patient is disconnected from the ventilator.

EXPECTED OUTCOMES

• Improved oxygenation
• Improved ventilation
• Improved patient-ventilator synchrony and comfort
• Alveolar recruitment
• Minimal ventilator-induced lung injury
• Reduced sedation requirements
• Liberation from mechanical ventilation

UNEXPECTED OUTCOMES

• Alveolar overdistention
• Alveolar derecruitment
• Patient-ventilator asynchrony
• Pneumothorax
• Worsening oxygenation
• Worsening ventilation
• Ventilator-associated event (VAE)
• Hemodynamic compromise

DOCUMENTATION

• P high
• P low
• T high
• T low
• MAP
• FIO₂
• T high:T low ratio (set)
• I:E ratio (actual)
• Pressure support
• Minute volume (total)
• Minute volume (spontaneous)
• Exhaled VT release breath
• Exhaled VT spontaneous breath
• Respiratory rate (total)
• Patient’s tolerance of procedure
• Education
• Unexpected outcomes and related interventions

REFERENCES

1. APRV-TCAV Network. (2020). APRV-TCAV standard guidelines 2020. Retrieved April 25, 2025, from https://www.tcavnetwork.org/download/aprv-tcav-standard-guidelines-2020/
2. Cairo, J.M. (2024). Chapter 5: Selecting the ventilator and the mode. In Pilbeam’s mechanical ventilation: Physiological and clinical applications (8th ed., pp. 62-84). St. Louis: Elsevier.
3. Cairo, J.M. (2024). Chapter 23: Special techniques used in ventilatory support. In Pilbeam’s mechanical ventilation: Physiological and clinical applications (8th ed., pp. 492-521). St. Louis: Elsevier.
4. Holt, G.A., Habib, S.A., Shelledy, D.C. (2020). Chapter 3: Principles of mechanical ventilation. In D.C. Shelledy, J.I. Peters (Eds.), Mechanical ventilation (3rd ed., pp. 95-154). Burlington, MA: Jones & Bartlett Learning.
5. NIH NHLBI ARDS Clinical Network. (n.d.). Mechanical ventilation protocol summary. Retrieved April 25, 2025, from http://www.ardsnet.org/files/ventilator_protocol_2008-07.pdf
6. Shelledy, D.C., Peters, J.I. (2020). Chapter 6: Ventilator initiation. In D.C. Shelledy, J.I. Peters (Eds.), Mechanical ventilation (3rd ed., pp. 311-366). Burlington, MA: Jones & Bartlett Learning.

ADDITIONAL READINGS

Othman, F. and others. (2021). The efficacy of airway pressure release ventilation in acute respiratory distress syndrome adult patients: A meta-analysis of clinical trials. Annals of Thoracic Medicine, 16(3), 245-252. doi:10.4103/atm.ATM_475_20

Shelledy, D.C., Peters, J.I. (2020). Chapter 7: Patient stabilization: Adjusting ventilatory support. In D.C. Shelledy, J.I. Peters (Eds.), Mechanical ventilation (3rd ed., pp. 367-400). Burlington, MA: Jones & Bartlett Learning.

Clinical Review: Jennifer Elenbaas, MA, BS, RRT, AE-C

Published: June 2025