Reclassifying Acute Respiratory Distress Syndrome

Area of Science:

• Critical Care Medicine
• Pulmonology
• Respiratory Physiology

Background:

• The PaO2/FiO2 (P/F) ratio is crucial for defining acute respiratory distress syndrome (ARDS) severity and guiding therapy.
• Current ARDS classification may benefit from refined thresholds to identify more homogeneous patient subgroups.

Purpose of the Study:

• To evaluate a 150-mm-Hg P/F threshold for creating more homogeneous subgroups within moderate ARDS.
• To identify clinical criteria associated with extracorporeal membrane oxygenation (ECMO) application in severe ARDS.

Main Methods:

• Patients with moderate ARDS (100-200 mm Hg P/F) were stratified using a 150-mm-Hg P/F threshold.
• Severe ARDS patients were subgrouped based on an 80% fraction of inspired oxygen (FiO2) threshold.
• Clinical and physiological parameters were compared between subgroups.

Main Results:

• The 150-mm-Hg P/F threshold divided moderate ARDS into mild-moderate (n=50) and moderate-severe (n=55) groups.
• Moderate-severe ARDS patients exhibited higher peak pressures, PaCO2, pH, lung weight, inhomogeneity, and recruitability.
• In severe ARDS, 75% of patients fell into the higher FiO2 subgroup; 41 of 46 ECMO patients were in this subgroup, with higher PaCO2 and lung parameters.

Conclusions:

• A 150-mm-Hg P/F threshold enhances ARDS subgroup homogeneity and reveals distinct anatomical/physiological characteristics.
• ECMO-treated patients predominantly belonged to the severe ARDS group with higher FiO2 requirements.
• This refined stratification aids in understanding ARDS heterogeneity and guiding advanced respiratory support decisions.