High-Flow Nasal Cannula for Respiratory Support in Adult ICU Patients: A Systematic Review

Background: High-flow nasal cannula (HFNC) is increasingly used for non-invasive respiratory support in adult ICU patients, mainly after extubation and in hypoxemic respiratory failure. Out study aim to evaluate the effectiveness of HFNC compared with conventional oxygen therapy, non-invasive ventilation (NIV), or non-invasive positive pressure ventilation in adult ICU patients requiring respiratory support. Methods: This systematic review followed PRISMA principles. We searched PubMed, Cochrane, Google Scholar, and other electronic databases for randomized controlled trials published between 2017 and 2025. Adult ICU studies comparing HFNC with conventional oxygen therapy, NIV, or non-invasive positive pressure ventilation were included. Overall, 466 records were identified, 421 remained after duplicate removal, 51 full texts were assessed, and 5 randomized controlled trials were included. Results: The included trials reported heterogeneous outcomes, including hospital length of stay, PaO2/FiO2 ratio, post-extubation vital signs, arterial blood gases, respiratory failure within 3 days after extubation, and 28-day mortality. HFNC associated with shorter hospital stay and fewer ICU readmissions in postoperative cardiac patients, improved oxygenation and reduced NIV use in severe hypoxemia after cardiac surgery, and provided comparable physiological Conclusion: HFNC is effective respiratory support option in selected adult ICU populations, mainly for oxygenation, comfort, and some post-extubation outcomes.