Background: Asthma is a chronic respiratory condition causing inflammation and changes to the airways. Care of people with asthma includes routine and urgent management across primary and tertiary care; however, due to sub-optimal long-term care and delays in obtaining help during acute exacerbations, the mortality and morbidity related to asthma is still a major health concern. There is reason to believe that non-invasive positive pressure ventilation (NPPV) could be beneficial to patients with severe acute asthma; however, the evidence surrounding the efficacy of NPPV is unclear, despite its common use in clinical practice.
Objectives: To determine the efficacy of NPPV in adults with severe acute asthma in comparison to usual medical care with respect to mortality, tracheal intubation, changes in blood gases and hospital length of stay.
Search methods: We carried out a search in the Cochrane Airways Group Specialised Register of trials (July 2012). Following this, the bibliographies of included studies and review articles were searched for additional studies (July 2012).
Selection criteria: We included randomised controlled trials of adults with severe acute asthma as the primary reason for presentation to the emergency department or for admission to hospital. Asthma diagnosis was defined by internationally accepted criteria. Studies were included if the intervention was usual medical care for the management of severe acute asthma plus NPPV applied through a nasal or facemask compared to usual medical care alone. Studies including patients with features of chronic obstructive pulmonary disease (COPD) were excluded unless data were provided separately for patients with asthma in studies recruiting both COPD and asthmatic patients.
Data collection and analysis: A combination of two review authors independently assessed trial quality and extracted data. Study authors were contacted for additional information where required. All data were analysed using RevMan 5.1. For continuous variables, a mean difference and 95% confidence interval were used and for dichotomous variables, risk ratio with 95% confidence interval were calculated.
Main results: We identified six trials for inclusion. Five studies on 206 participants contributed data, while one study was available in abstract form only and was not fully incorporated into this review. For the primary outcome of endotracheal intubation there were two studies that contributed data: two intubations were needed in 45 participants on NPPV and no intubations in 41 control patients (risk ratio 4.48; 95% CI 0.23 to 89.13). There were no deaths in either of these studies. Length of hospital stay was reported in two studies, though meta-analysis was not possible. Hospitalisation was reported in one small study, in which there were three admissions out of 17 on NPPV and 10 admissions out of 16 in control patients (RR 0.28, 95% CI 0.09, 0.84).
Authors' conclusions: This review of studies has highlighted the paucity of data that exist to support the use of NPPV in patients in status asthmaticus. As such this course of treatment remains controversial despite its continued use in current clinical practice. Larger, prospective randomised controlled trials of rigorous methodological design are needed to determine the role of NPPV in patients with asthma.