A Cochrane review [Abstract] 1 on the effect of non-invasive positive pressure ventilation (NIPPV) in stable chronic obstructive pulmonary disease (COPD) included 7 studies with a total of 245 subjects. The analyses were based on individual patient data. The 95% confidence interval (CI) included zero for all outcomes, including partial pressure of CO2 and O2 in arterial blood, six-minute walking distance (6MWD), health-related quality of life (HRQoL), forced expiratory volume in one second (FEV1), forced vital capacity (FVC), maximal inspiratory pressure (PImax) and sleep efficiency. The mean effect on 6MWD was small at 27.7 m (95% CI -28.1 to 66.3 m) and not statistically significant, but given the width of the confidence interval, the real effect of NIPPV on 6MWD remains uncertain, and a clinically significant effect cannot be excluded.
Comment: The quality of evidence is downgraded by imprecise results (few patients and wide confidence intervals).
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