Non-invasive positive pressure ventilation for treatment of respiratory failure due to severe acute exacerbations of asthma.

BACKGROUND Non-invasive positive pressure ventilation (NPPV) has been shown to be effective in chronic obstructive pulmonary disease patients with acute respiratory failure. However, its role in patients with severe acute asthma is uncertain. The pathophysiologic condition of acute respiratory failure in asthma is in many ways similar to that of acute respiratory failure in COPD. Therefore, there is reason to believe that NPPV could also be successful in patients with severe acute asthma. 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 STRATEGY An initial search for studies was carried out using CENTRAL. Additional searches were also carried out on MEDLINE, EMBASE, CINAHL, Science Citation, web based clinical trials databases and key journals with web sites were also searched as well as respiratory conference proceedings. Following this, the bibliographies of each randomised controlled trial obtained (and any review articles) was searched for additional studies. Date of most recent search for trials was conducted on May 2004. SELECTION CRITERIA Only RCTs in adults patients with severe acute asthma were considered for inclusion. Studies including patients with features of COPD were excluded unless data was provided separately for patients with asthma in studies recruiting both COPD and asthma patients. DATA COLLECTION AND ANALYSIS All data was analysed using RevMan. For continuous variables, a weighted mean difference and 95% confidence interval (95%CI) was calculated for each study outcome. For dichotomous variables relative risk with 95% confidence interval was calculated. MAIN RESULTS From an initial search of 696 abstracts, 11 trials were obtained in full-text for closer examination. Ten trials were excluded and one included. The one included trial, on 30 patients, showed benefit with NPPV when compared to usual medical care alone with significant improvements in hospitalisation rate, number of patients discharged from emergency department, percent predicted FEV(1), FVC, PEFR and respiratory rate. AUTHORS' CONCLUSIONS The application of NPPV in patients suffering from status asthmaticus, despite some interesting and very promising preliminary results, still remains controversial. Large, prospective, randomised controlled trials are therefore needed to determine the role of NPPV in status asthmaticus.