Abstract
Over the past decade and boosted by the coronavirus disease 2019 (COVID-19) pandemic, high-flow nasal oxygen (HFNO) has been increasingly used in the intensive care unit (ICU) to treat acute hypoxemic respiratory failure (AHRF). In this review, we show that despite this wide and rapid increase in the use of HFNO to treat AHRF, HFNO does not fulfill all the criteria of a “reference treatment”. First, there are some inconsistencies between the studies that provided a positive signal toward the possible benefit of HFNO in AHRF. The two high-quality studies were negative in terms of primary outcome although they provided promising signals in favor of HFNO in terms of secondary outcomes or unplanned secondary analysis. The significance of the only positive study suffers from notable limitations and other trials, conducted in COVID-19 and in immunocompromised patients, are definitely negative and do not even provide promising signals in favor of HFNO. Of note, authors of some of the large randomized controlled trials (RCTs) on HFNO have received grants or personal fees from manufacturers of HFNO devices. Second, meta-analyses do not show positive results regarding the efficacy of HFNO on mortality and recent guidelines do not support its use to improve this outcome, although they recommend HFNO use to reduce intubation rate. Third, HFNO is associated with risks that should be accounted for. There are concerns that HFNO may delay intubation, which is in turn associated with higher mortality and prolonged length of stay. In addition, with HFNO, high inspiratory effort may generate high lung strain and overstretch, a phenomenon termed patient self-inflicted lung injury (P-SILI). Fourth, there are concerns regarding access to HFNO in resource-limited settings. Fifth, there are also concerns regarding the deleterious environmental impact of HFNO due to the high volume of consumables and high oxygen flow, which remain to be precisely quantified and balanced with the potential reduction in intubation rate. Considering all these limitations, HFNO is not yet the reference treatment for AHRF.
Key Points
- Conflicting Trial Outcomes: Randomized controlled trials (RCTs) evaluating HFNO in AHRF have produced mixed results, with some showing potential benefits in reducing intubation rates, while others demonstrate no impact on mortality, leaving its overall efficacy inconclusive.
- Comparison with Conventional Oxygen Therapy: Although HFNO reduces intubation rates compared to conventional oxygen therapy (COT), its benefits do not consistently translate into improved survival outcomes, undermining its status as a definitive treatment for AHRF.
- Comparison with CPAP and NIV: Continuous positive airway pressure (CPAP) and helmet non-invasive ventilation (NIV) have shown greater efficacy than HFNO in reducing intubation rates, suggesting their potential superiority in certain patient populations.
- Meta-Analysis Findings: Meta-analyses highlight HFNO’s modest impact on preventing intubation but fail to demonstrate significant mortality benefits, raising questions about its broader clinical utility.
- Delayed Intubation Risk: HFNO may delay necessary intubation, which is associated with worsened outcomes, including higher mortality rates and prolonged ICU stays.
- Patient Self-Inflicted Lung Injury (P-SILI): High inspiratory efforts during HFNO can exacerbate lung injury, leading to conditions similar to ventilator-induced lung injury, especially in patients with severe AHRF.
- Challenges in Low-Resource Settings: Limited access to HFNO devices, high costs, and infrastructure demands, such as reliable oxygen supplies, hinder its use in low- and middle-income countries, particularly during health crises like COVID-19.
- Environmental Impact: HFNO’s high oxygen flow requirements contribute to increased carbon emissions and waste generation, raising sustainability concerns in intensive care settings.
- Guideline Limitations: Current clinical guidelines recommend HFNO to reduce intubation rates but fail to endorse it for reducing mortality, reflecting the need for stronger evidence.
- Future Research Needs: Further studies are required to address HFNO’s efficacy, refine patient selection criteria, and evaluate alternative therapies with greater clinical and environmental benefits.
