Abstract: Objective: To investigate the clinical effect of noninvasive positive pressure ventilation(NPPV) on patients with chronic obstructive pulmonary disease(COPD) complicated with respiratory failure,and the factors affecting the results.Methods: One hundred and forty-four patients with COPD complicated with respiratory failure were divided into conventional therapy group and NPPV therapy group.The patients' age,COPD history,heart rate at 2,24 hours before and after the therapy,respiratory rate,systolic and diastolic pressure,body temperature,blood white cell counting,blood sodium,arterial blood gas(pH、PaCO₂、PaO₂),oxygenation index(PaO₂/FiO₂) and Glasgow coma score were recorded and analyzed.Results: In the NPPV group,there was a significant improvement of PaO₂ and pH at 2 hours after the therapy,while PaCO₂ descended.The other indexes further improved at 24 hours after the therapy(P<0.05).In the conventional therapy group,PaCO₂ and pH did not improve significantly at 2 hours after the therapy(P>0.05) but there was a significant improvement of PaO₂ at 24 hours after the therapy(P<0.05),anyhow,the improvement was not as significant as the NPPV group(P<0.01).The rate of failed treatment and end tracheal intubation in the NPPV group was markedly lower than that in the conventional therapy group(P<0.05).Aged patients,patients with severe respiratory acidosis,high PaCO₂ or in a coma had a higher risk of failure.Conclusions: Noninvasive positive pressure ventilation is effective for patients with COPD complicated with respiratory failure.Aged patients and patients with serious respiratory acidosis or heavy CO₂ retention should resort to tracheal intubation if NPPV failed to act.