Background This meta-analysis evaluated the effect of noninvasive,positive pressure ventilation on severe,stable chronic obstructive pulmonary disease (COPD).Methods PUBMED,CNKI,Wanfang,EMBASE and the Cochrane trials databases were searched.Randomized controlled trials of patients with severe,stable COPD and receiving noninvasive positive pressure ventilation,compared with sham ventilation or no ventilation,were reviewed.The mortality,physiological and health related parameters were pooled to yield odds ratio (OR),weighted mean differences or standardized mean differences (SMD),with 95％ confidence interval (C/).Results Eight parallel and three crossover randomized controlled trials met the inclusion criteria.Pooled analysis for parallel,randomized controlled trials showed noninvasive positive pressure ventilation:(1) Did not affect the 12-or 24-month mortality (OR 0.82,95％ C/:0.48 to 1.41); (2) Improved the arterial carbon dioxide tension (SMD-0.88,95％C/:-1.43 to-0.34); (3) Did not improve forced expiratory volume in one second (SMD 0.20,95％ C/:-0.06 to 0.46),maximal inspiratory pressure (SMD 0.01,95％ C/:-0.28 to 0.29) or 6-minute walk distance (SMD 0.17,95％ C/:-0.16 to 0.50); (4) Subgroup analysis showed noninvasive positive pressure ventilation improved the arterial carbon dioxide tension in hypercapnic patients.Pooled analysis for crossover randomized controlled trials did not show improvement in arterial blood gas or forced expiratory volume in one second with noninvasive positive pressure ventilation.Conclusions Noninvasive positive pressure ventilation improves the arterial carbon dioxide tension but does not improve the mortality,pulmonary function,or exercise tolerance and should be cautiously used in severe stable chronic obstructive pulmonary disease.