Tidal volume variability during airway pressure release ventilation: case summary and theoretical analysis

Area of Science:

• Critical Care Medicine
• Respiratory Physiology
• Mechanical Ventilation

Background:

• Airway pressure-release ventilation (APRV) is a pressure control mode facilitating spontaneous breathing in severe respiratory failure.
• Limited data exist on the variability and safety of tidal volumes (V(T)) during APRV and bi-level positive airway pressure modes.

Observation:

• Serial V(T) measurements in a severe ARDS patient on APRV revealed significant variation (4-12 mL/kg predicted body weight).
• Computed tomography and radiographs showed lung parenchyma changes potentially linked to ventilator-induced lung injury post-APRV.

Findings:

• A mathematical model highlighted the interdependence of release volume, autoPEEP, and T(low) in APRV.
• Targeting specific P(aCO(2)) with desired V(T) and autoPEEP is challenging in passive models, underscoring spontaneous breathing's role.

Implications:

• This case report and model analysis suggest caution with APRV, emphasizing the need to limit end-inspiratory lung volumes to prevent injury.
• Effective APRV application requires advanced knowledge and skill beyond basic literature descriptions.