Heliox in the treatment of chronic obstructive pulmonary disease

Objective: To determine if breathing helium oxygen mixtures in addition to conventional therapy in nonintubated adult chronic obstructive airways disease ( COPD) patients reduces the arterial partial pressure of carbon dioxide (PaCO2) more than conventional treatment alone, and confers an advantage in terms of the odds of intubation in the acute setting. Design: Meta-analysis. Setting: Diverse settings. Participants: Adult patients with a diagnosis of either stable severe or acute COPD. Main outcome measures: Decrease in partial pressure of arterial PaCO2 and intubation rates. Results: Combination of the results from trials measuring change in PaCO2 in COPD subjects receiving conventional therapy but breathing helium-oxygen estimated a reduction of 0.78 KPa (1.44-0.13) beyond that produced by conventional therapy with air-oxygen breathing (n = 234). Using quantitative and qualitative measures of validity it was found that most trials were unsatisfactory. Chief concerns were poor concealment of allocation and lack of blinding. Analysis excluding all papers with low methodological quality (Jadad<2) estimated the reduction in PaCO2 conferred by use of Heliox breathing to be 0.22 KPa (+0.57 to -0.14). A non-significant reduction (p=0.2). When combined, the results from trials measuring the intubation rates of patients treated conventionally or with Heliox (n=121) the odds ratio of intubation was 0.096 (0.03-0.27). Conclusion: Definitive evidence of a beneficial role of Heliox in treatment of severe COPD is lacking and therefore its wide scale use cannot be recommended based on this analysis. However, as a beneficial effect of Heliox breathing was reported in all trials, further investigation with a well conducted randomised controlled trial is warranted.