[Oxygen therapy undisputed in severe, but doubtful in moderate, hypoxia. Comment to meta-analysis of home oxygen therapy in chronic obstructive lung disease].

The review included randomized controlled trials on patients with chronic obstructive pulmonary disease (COPD) receiving domiciliary long-term oxygen therapy (LTOT). The authors identified six articles concerning four randomized controlled trials but could not perform any meta-analysis due to the heterogenous patient populations and treatments. From these trials they conclude that LTOT improves survival in patients with severe hypoxemia (arterial PaO2 less than 8 kPa) but has no effect in patients desaturating only at night or in patients with moderate hypoxemia. They also sensibly remark that it is possible that statistically significant improvements in some physiological variables have little measurable impact on subjects perceived quality of life or survival. The conclusion that survival benefit is demonstrated also in patients with hypoxemia in the range 7,4-8 kPa is debatable, with the strongest evidence pointing against benefit. These patients are better classified as moderately hypoxemic. In Sweden, they comprise 20% of new patients starting on LTOT. For them, the effect of LTOT should be evaluated individually in terms other than survival or quality of life. A more recently published trial supports the conclusion that domiciliary nocturnal oxygen therapy has no impact on survival in nocturnal desaturation without severe daytime hypoxemia. There is also new evidence that the type of oxygen equipment might have a decisive impact on the quality of life in mobile patients receiving LTOT--improved quality of life with liquid oxygen and poorer quality of life with concentrator and conventional (heavy) gas cylinder. The importance of optimum equipment selection for each patient has been overlooked but merits further investigation.