The Impact of High-Flow Nasal Oxygen in the Immunocompromised Critically Ill: A Systematic Review and Meta-Analysis

High-flow nasal-cannula (HFNC) may be an oxygen modality useful for preventing invasive mechanical ventilation and mortality; however, its role in acute hypoxemic respiratory failure is not clearly defined. We sought to evaluate the impact of HFNC on mortality across immunocompromised subjects compared to alternative noninvasive oxygen therapies, namely conventional oxygen therapy and noninvasive ventilation (NIV).

We systematically searched the major databases to identify randomized, controlled trials (RCTs) or observational studies (until May 2018). We included studies reporting the use of HFNC in immunocompromised subjects and evaluated its impact on mortality and invasive mechanical ventilation.

Upon review of 6,506 titles, 13 studies (1,956 subjects) fulfilled our inclusion criteria (4 RCTs, 9 observational studies). The predominant cause of immunocompromised status was cancer. Bacterial pneumonia was the most common cause of acute hypoxemic respiratory failure with a median P_aO2/F_IO2 of 145 mm Hg (interquartile range 115-175). HFNC was used as the first oxygen strategy in 474 subjects compared to NIV (242 subjects) and conventional O₂ therapy (703 subjects). There was a 46% rate of invasive mechanical ventilation and 36% mortality. Mortality at the longest available follow-up was lower with HFNC compared to the oxygen therapy controls (NIV or conventional O₂ therapy) in 7 studies (1,429 subjects; relative risk 0.72, 95% CI 0.56-0.93, P = .01). There was a lower rate of invasive mechanical ventilation with HFNC compared to the oxygen therapy controls across 8 studies (1,529 subjects, relative risk 0.81, 95% CI 0.67-0.96, P = .02). These results were robust across a series of sensitivity analyses.

There exists a need to develop a greater evidence base evaluating the utility of HFNC in immunocompromised subjects. In our exploratory analysis, HFNC was found to decrease mortality and use of invasive mechanical ventilation compared to alternative noninvasive oxygen controls. These results are meant to be exploratory. Higher-quality studies evaluating a more homogeneous population are needed to further elucidate its benefit.