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There is limited evidence to recommend use of noninvasive positive-pressure ventilation in patients with respiratory failure from severe asthma exacerbations.

Methods

Data Sources

The Cochrane Airways Group searched their specialized register of trials, composed of Central Register of Trials, MEDLINE, EMBASE, Cumulative Index to Nursing and Allied Health Literature, The Allied and Complementary Medicine Database, and PsychINFO, and hand searched respiratory journals and meeting abstracts. Clinical trial registries for ongoing and recently completed studies were included. Manufacturing companies for ventilators were contacted to identify further research studies. The last search was July 2012.

Study Selection

Randomized controlled trials comparing use of usual medical care plus noninvasive positive-pressure ventilation to usual care only in adult patients (aged ≥18 years) with respiratory failure caused by severe asthma exacerbations were analyzed. Studies involving patients with Chronic Obstructive Pulmonary Disease or asthma were included if there were separate data for the patients with asthma. Trials of patients with pneumonia or acute respiratory distress syndrome were not included.

Data Extraction, Measurement, and Synthesis

Three review authors independently reviewed literature to search for studies meeting inclusion criteria. Two review authors extracted data onto standardized forms. Assessment of bias was conducted by grading of allocation sequence generation, allocation concealment, blinding of participants and outcome assessors, incomplete data, and selective outcome reporting and other threats to validity. Continuous outcomes are presented as mean difference with 95% confidence interval (CI). Dichotomous outcomes are presented as relative risk (RR) with 95% CIs. Heterogeneity was assessed with the I2 statistic.

Results : From 746 abstracts, only 5 randomized controlled trials with total of 203 patients were chosen; all patients had acute severe asthma as primary diagnosis. Four of the 5 studies used biphasic positive airway pressure and 1 used continuous positive airway pressure. Two of the studies adjusted respiratory pressure settings according to the patients' clinical parameters, whereas 3 used standardized respiratory pressures. There was no evidence to suggest improved primary outcomes and poor evidence to suggest improved secondary outcomes with noninvasive positive-pressure ventilation ...