Introduction: Acute hypoxemic respiratory failure (AHRF) is the most common cause of critical illness in immunocompromised patients. High-flow nasal-cannula (HFNC) may be an oxygen modality useful for preventing mechanical ventilation and reducing mortality. The mechanisms of effect include washout of carbon dioxide from the anatomical dead space, generation of positive end expiratory pressure (PEEP), and more stable fraction of inspired oxygen due to the higher flows administered. Its role in acute hypoxemic respiratory failure (AHRF) in the immunocompromised, critically ill adult, however is not clearly defined.
Objectives: We sought to evaluate the impact of HFNC across immunocompromised subjects on mortality compared to alternative non-invasive oxygen therapies (conventional oxygen therapy (COT) or non-invasive ventilation (NIV).
Methods: 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/invasive mechanical ventilation.
Results: Upon review of 6505 titles, 13 studies (1956 subjects) fulfilled our inclusion criteria (4 RCTs, 9 observational). The overall risk of bias from the RCTs was low and the median Newcastle-Ottawa score for observational studies was 8. The predominant cause of immunocompromised status was malignancy. Bacterial pneumonia was the most common cause of AHRF with a median PaO2/FiO2 of 145 (IQR 115-175) mmHg. HFNC was used as the first oxygen strategy in 474 subjects compared to NIV (242) and COT (703). The rate of invasive mechanical ventilation and mortality was 46% and 36% respectively. Mortality at the longest available follow-up was lower with HFNC compared to the oxygen therapy controls (NIV or COT) in 7 studies (1429 patients; RR 0.72; 95%CI 0.56-0.93; p = 0.01). There was a lower rate of invasive mechanical ventilation with HFNC compared to the oxygen therapy controls across 8 studies (1529 patients, RR 0.81; 95%CI 0.67-0.96; p =0.02). These results were robust across a series of sensitivity analyses. In subgroup analyses across 4 studies, HFNC compared to NIV was found to be associated with a decreased mortality (545 subjects; RR 0.60; 95% CI 0.37-0.97; p 0.04) but not COT across 5 studies (1097 subjects; RR 0.80; 95% CI 0.62-1.05; p 0.1). In the subgroup analysis comparing HFNC to NIV, there was no difference in rates of invasive mechanical ventilation across 4 studies (545 subjects; RR 0.67; 95% CI 0.43-1.04; p 0.07). There was also no difference in rates of invasive mechanical ventilation comparing HFNC to COT across 6 studies (1197 subjects; RR 0.90; 95% CI 0.78-1.03; p=0.12).
Conclusions: HFNC is a unique oxygen delivery modality that holds theoretical promise for the treatment of AHRF in immunocompromised patients. 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 invasive mechanical ventilation compared to alternative non-invasive oxygen controls, but given the inherent biases of the trials, these results are meant to be exploratory. Higher quality studies evaluating a more homogeneous population are needed to further elucidate its benefit.
Introduction: Acute hypoxemic respiratory failure (AHRF) is the most common cause of critical illness in immunocompromised patients. High-flow nasal-cannula (HFNC) may be an oxygen modality useful for preventing mechanical ventilation and reducing mortality. The mechanisms of effect include washout of carbon dioxide from the anatomical dead space, generation of positive end expiratory pressure (PEEP), and more stable fraction of inspired oxygen due to the higher flows administered. Its role in acute hypoxemic respiratory failure (AHRF) in the immunocompromised, critically ill adult, however is not clearly defined.
Objectives: We sought to evaluate the impact of HFNC across immunocompromised subjects on mortality compared to alternative non-invasive oxygen therapies (conventional oxygen therapy (COT) or non-invasive ventilation (NIV).
Methods: 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/invasive mechanical ventilation.
Results: Upon review of 6505 titles, 13 studies (1956 subjects) fulfilled our inclusion criteria (4 RCTs, 9 observational). The overall risk of bias from the RCTs was low and the median Newcastle-Ottawa score for observational studies was 8. The predominant cause of immunocompromised status was malignancy. Bacterial pneumonia was the most common cause of AHRF with a median PaO2/FiO2 of 145 (IQR 115-175) mmHg. HFNC was used as the first oxygen strategy in 474 subjects compared to NIV (242) and COT (703). The rate of invasive mechanical ventilation and mortality was 46% and 36% respectively. Mortality at the longest available follow-up was lower with HFNC compared to the oxygen therapy controls (NIV or COT) in 7 studies (1429 patients; RR 0.72; 95%CI 0.56-0.93; p = 0.01). There was a lower rate of invasive mechanical ventilation with HFNC compared to the oxygen therapy controls across 8 studies (1529 patients, RR 0.81; 95%CI 0.67-0.96; p =0.02). These results were robust across a series of sensitivity analyses. In subgroup analyses across 4 studies, HFNC compared to NIV was found to be associated with a decreased mortality (545 subjects; RR 0.60; 95% CI 0.37-0.97; p 0.04) but not COT across 5 studies (1097 subjects; RR 0.80; 95% CI 0.62-1.05; p 0.1). In the subgroup analysis comparing HFNC to NIV, there was no difference in rates of invasive mechanical ventilation across 4 studies (545 subjects; RR 0.67; 95% CI 0.43-1.04; p 0.07). There was also no difference in rates of invasive mechanical ventilation comparing HFNC to COT across 6 studies (1197 subjects; RR 0.90; 95% CI 0.78-1.03; p=0.12).
Conclusions: HFNC is a unique oxygen delivery modality that holds theoretical promise for the treatment of AHRF in immunocompromised patients. 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 invasive mechanical ventilation compared to alternative non-invasive oxygen controls, but given the inherent biases of the trials, these results are meant to be exploratory. Higher quality studies evaluating a more homogeneous population are needed to further elucidate its benefit.