Objective: To examine whether patients with acute hypoxemia and bilateral opacities treated with high-flow nasal cannula and acute respiratory distress syndrome patients who were directly mechanically ventilated are similar in terms of lung epithelial, endothelial, and inflammatory biomarkers.
Design: Prospective, multicenter study.
Setting: ICUs at three university tertiary hospitals.
Patients: Intubated and nonintubated patients admitted to the ICU with acute hypoxemia (PaO2/FIO2 ≤ 300) and bilateral opacities.
Interventions: None.
Measurements and main results: Either high-flow nasal cannula or mechanical ventilation was initiated, at the discretion of the attending physician. We measured plasma biomarkers of lung epithelial injury (receptor for advanced glycation end products and surfactant protein D) and endothelial injury (angiopoietin-2) and inflammation (interleukin-6, interleukin-8, and interleukin-33 and soluble suppression of tumorigenicity-2) within 24 hours of acute respiratory distress syndrome onset. Propensity score matching was performed using six different variables (Acute Physiology and Chronic Health Evaluation II, Sequential Organ Failure Assessment, PaO2/FIO2, origin of acute respiratory distress syndrome, steroids, renal failure and need for vasopressors). Nonhypoxemic mechanically ventilated critically ill patients and healthy volunteers served as controls. Of the 170 patients enrolled, 127 (74.7%) were intubated and 43 (25.3%) were treated with high-flow nasal cannula at acute respiratory distress syndrome onset. After propensity score matching (39 high-flow nasal cannula patients vs 39 mechanical ventilation patients), no significant differences were observed in receptor for advanced glycation end products, surfactant protein D, angiopoietin-2, interleukin-6, interleukin-8, interleukin-33, and soluble suppression of tumorigenicity-2 between matched patients who were treated with high-flow nasal cannula and those who were intubated at acute respiratory distress syndrome onset. After matching, no differences in mortality or length of stay were observed. All biomarkers (with the exception of interleukin-33) were higher in both groups of matched acute respiratory distress syndrome patients than in both control groups.
Conclusions: Acute hypoxemic patients with bilateral infiltrates treated with high-flow nasal cannula presented a similar pattern of biomarkers of inflammation and injury to acute respiratory distress syndrome patients undergoing direct mechanical ventilation. The results suggest that these high-flow nasal cannula patients should be considered as acute respiratory distress syndrome patients.