ICU · Respiratory

Acute respiratory distress syndrome: phenotyping and personalised ventilation

Also known as ARDS phenotypes · Personalised ventilation · Hyperinflammatory vs hypoinflammatory ARDS · Recruitment manoeuvres · Driving pressure · ARDS subphenotypes · Latent class analysis ARDS · Precision medicine ARDS · Focal vs non-focal ARDS · Direct vs indirect lung injury · Recruitable lung

ARDS is not a single disease — two distinct phenotypes have been identified. Hyperinflammatory ARDS (high inflammatory markers, vasopressor-dependent, lower mortality with higher PEEP): responds better to higher PEEP and prone positioning. Hypoinflammatory ARDS (lower inflammatory markers, more extrapulmonary cause): may not benefit from aggressive PEEP. Personalised ventilation: individualise PEEP based on recruitability (PEEP titration by P-V curves, EIT, oesophageal pressure), driving pressure (<15 cmH2O — Amato meta-analysis: driving pressure is the strongest predictor of mortality), and lung morphology (focal vs non-focal on CT — focal ARDS tolerates higher PEEP poorly). Recruitment manoeuvres controversial (ART trial: caused harm). Prone positioning beneficial for moderate-severe ARDS (PaO2/FiO2 <150). Latent class analysis of the ALVEOLI and FACTT trials (Calfee 2014) identified the hyperinflammatory (type 2) and hypoinflammatory (type 1) subphenotypes using biomarkers — IL-6, IL-8, soluble TNF receptor-1, angiopoietin-2, bicarbonate, protein C. The subphenotype determines treatment response: higher PEEP and simvastatin benefit the hyperinflammatory phenotype but may harm the hypoinflammatory phenotype (HARP-2 secondary analysis, Calfee 2018). Precision medicine in ARDS is evolving but not yet routine bedside practice.