[A new indicator to determine the optimal PEEP (author's transl)]

Area of Science:

• Critical Care Medicine
• Respiratory Physiology
• Cardiopulmonary Research

Background:

• Optimal Positive End-Expiratory Pressure (PEEP) is crucial for managing patients with Acute Respiratory Distress Syndrome (ARDS).
• Traditional methods like Suter's best PEEP, based on maximal oxygen transport, have practical limitations in clinical settings.
• Oxygen transport often peaks at Zero End-Expiratory Pressure (ZEEP), complicating its use as a sole indicator for optimal PEEP.

Purpose of the Study:

• To investigate and identify a more reliable indicator for determining the optimal PEEP in ARDS patients.
• To evaluate the efficacy of 'intrapulmonary non-shunt flow (Qt-Qs)' as a novel parameter for PEEP optimization.
• To establish criteria for optimal PEEP that balance shunt reduction with minimal impact on cardiac output.

Main Methods:

• Respiratory and hemodynamic assessments were conducted on 12 normovolemic ARDS patients.
• Studies involved varying levels of PEEP (0, 5, 10, 20 cm H2O).
• Measurements included oxygen transport, intrapulmonary shunt flow, and cardiac output.

Main Results:

• Maximal oxygen transport was frequently observed at PEEP=0 (ZEEP), rendering it impractical for guiding optimal PEEP.
• The proposed 'intrapulmonary non-shunt flow (Qt-Qs)' emerged as a potential new indicator.
• Optimal PEEP was associated with maximizing intrapulmonary non-shunt flow while minimizing cardiac output reduction.

Conclusions:

• Suter's best PEEP based on maximal oxygen transport is not clinically applicable for optimizing PEEP in ARDS.
• Intrapulmonary non-shunt flow (Qt-Qs) presents a promising new metric for setting optimal PEEP.
• Optimal PEEP should be selected to maximize intrapulmonary non-shunt flow, ensuring minimal compromise to cardiac output.