APRV Settings and Clinical Application

Introduction

• Informal workshop discussion on APRV settings.
• Focus on practical settings rather than research data.
• Goal: Prevent acute lung injury (ARDS) and ICU diseases.
• Emphasis on prevention and maintaining normal lung function.

Background on APRV

• APRV: CPAP-type breath with patient superimposing their breathing pattern.
• CPAP is intermittently released to aid in metabolic loading.
• APRV uses pressure for favorable inspiration, aiming at the compliant part of the pressure-volume curve.
• Main settings: PN span (pressure control), respiratory rate, and waveform graphics.
• Key principle: Make it as much CPAP as possible.

Key Settings and Methodologies

APRV Basics

• CPAP phase is critical; releases should total around 2 minutes per 10 breaths.
• Goal: Maintain alveolar volume to aid in gas exchange and prevent lung injury.
• APRV integrates diffusive and convective ventilation.

Spontaneous Breathing and Patient Positioning

• Encourage spontaneous breathing within 24 hours of admission if possible.
• APRV enables spontaneous breathing without causing harm (unlike full sedation or paralysis).
• Spontaneous breathing distributes ventilation more evenly, reducing pleural pressure.
• Additional benefits include better diaphragm function and reduced ICU complications.

PEEP and Alveolar Stability

• Importance of maintaining alveolar stability through controlled time (P low of zero, T low settings).
• Flow patterns are used to estimate lung volume rather than relying on pressure only.
• Correctly set APRV minimizes alveolar instability and histopathology.

P High and Compliance

• P High (pressure high) is used to counteract the worsening compliance due to resuscitation and edema.
• Continuous pressure helps in maintaining lung volume.
• Recruitment maneuvers should be continuous and align with the patient’s pressure-volume curve.
• Balance between high and low lung volumes to maintain optimal pulmonary vascular resistance.

Clinical Applications

Implementing APRV in ICU

• Early use in patients to prevent lung injury and maintain spontaneous breathing.
• Diuretic approach to manage edema and improve lung compliance.
• Challenges with hypercarbia are managed by adjusting P High and T High, not T Low.
• Extending T High increases diffusion, aiding in CO2 removal without increasing rate.

Weaning and Patient Comfort

• Weaning involves increasing CPAP blocks and transitioning ventilation responsibility to the patient.
• Assess work of breathing and adjust based on patient’s capacity.
• Use of Dexmedetomidine for sedation to facilitate early mobilization and breathing.
• Stretch tests and monitored breathing trials to determine readiness for extubation.
• Gradual reduction in pressure while maintaining lung volume to prevent extubation failure.

Advanced Clinical Considerations

• Adjust APRV settings based on patient’s condition (e.g., compliance, edema, abdominal pressure).
• Focus on maintaining a homogeneous lung to reduce injury and improve outcomes.
• Use of capnography and other monitoring tools to fine-tune settings and ensure patient comfort.

Summary

• APRV is a strategy that combines CPAP with intermittent releases to maintain alveolar stability and promote spontaneous breathing.
• Proper setting adjustment based on individual patient needs can prevent lung injury and aid in efficient ventilation.
• Early mobilization, patient comfort, and continuous monitoring are key aspects of successful APRV implementation.