Noninvasive Ventilation in Acute Asthma Exacerbations: A Systematic Review

Rationale: Because of a paucity of evidence, multiple clinical practice guidelines lack recommendations pertaining to noninvasive ventilation (NIV) in acute asthma exacerbations. However, the evidence syntheses for these guidelines were performed years ago, and more recent randomized controlled trials (RCTs) and observational studies have been published. Objectives: We sought to update the evidence syntheses from previous guidelines to further clarify the effects of NIV in acute asthma exacerbations. Methods: A systematic search of Medline, Embase, and the Cochrane Library was conducted, studies comparing NIV plus standard medical therapy with standard medical therapy alone in adults with acute asthma exacerbations were selected using a priori selection criteria, and relevant data were extracted. Weighted aggregation (meta-analysis) was performed to summarize effects, which were appraised using the Grading of Recommendations, Assessment, Development, and Evaluation (or, GRADE) approach. Results: Eight RCTs and five observational studies were selected. NIV was associated with a reduced intubation rate (RCTs: risk ratio [RR] = 0.46; 95% confidence interval [CI] = 0.16 to 1.29; observational studies: RR = 0.55; 95% CI = 0.45 to 0.68), admission rate (RR = 0.57; 95% CI = 0.34 to 0.98), and time to improvement in accessory muscle use (mean difference = -1.13 h; 95% CI = -1.28 to -0.99). Additional outcomes favored NIV plus standard medical therapy but did not reach statistical significance, including dyspnea measures and spirometry measures. There were too few deaths to assess mortality reliably. The quality of evidence ranged from low to very low for all outcomes. Conclusions: All statistically significant outcomes favored NIV plus standard medical therapy over standard medical therapy alone in adults with acute asthma exacerbations. Our aggregate data suggest that intubation rate may be reduced with NIV plus standard medical therapy, although the overall quality of the evidence is low. If this is a true effect, it may be clinically important, because intubation has been shown to correlate with mortality in multiple observational trials. Given these findings, patients with acute asthma exacerbations may benefit from a trial of NIV in addition to standard medical therapy.