High-Flow Nasal Cannula Outside the ICU: A Systematic Review and Meta-Analysis.

Area of Science:

• Critical Care Medicine
• Respiratory Therapy
• Health Services Research

Background:

• High-flow nasal cannula (HFNC) use has grown beyond intensive care units (ICUs) to general and step-up respiratory wards.
• Safety and effectiveness of HFNC in non-ICU settings remain under investigation, particularly post-pandemic.
• Existing evidence is limited, necessitating a comprehensive review of its application in diverse hospital environments.

Purpose of the Study:

• To systematically review and meta-analyze the safety and effectiveness of HFNC initiated in non-ICU settings.
• To compare HFNC outcomes, including mortality and ICU transfer rates, across different non-ICU environments (general wards vs. step-up units).
• To evaluate HFNC versus conventional oxygen therapy (COT) in do-not-intubate (DNI) patient cohorts.

Main Methods:

• Systematic review and meta-analysis of observational studies and trials involving adult patients initiated on HFNC in non-ICU wards.
• Primary outcomes assessed were in-hospital or 28-day mortality and ICU transfer.
• Random-effects models were used for synthesis, with risk of bias and certainty of evidence assessed using ROBINS-I/RoB 2 and GRADE criteria.

Main Results:

• Across all non-ICU wards, pooled mortality was 14.0% and ICU transfer was 20.0%.
• Internal medicine/respiratory wards showed higher pooled mortality (19.8%) and ICU transfer (31.2%) compared to step-up units (22.0% transfer).
• Evidence certainty for critical outcomes was very low due to study design, inconsistency, and imprecision.

Conclusions:

• HFNC is feasible outside the ICU but associated with significant mortality and escalation, especially on general wards.
• Step-up units (IMCU/HDU) showed more consistent HFNC outcomes, suggesting environment-dependent results.
• Institutions should implement protocolized reassessment and rapid response systems for ward-based HFNC, given low certainty evidence.