A Cochrane review [Abstract] 1 included 20 studies. FEV1 improved with treatment: WMD 100 ml; 95% CI 40 to 160 ml. Similarly for FVC: WMD 210 ml, 95% CI 100 to 320 ml. Two studies reported an improvement in VO2max; WMD 195 ml/min, 95% CI 113 to 278 ml/min. At rest, PaO2 and PaCO2 both improved with treatment (WMD 3.2 mmHg; 95% CI 1.2 to 5.1 mmHg, and WMD -2.4 mmHg; 95% CI -3.5 to -1.2 mmHg, respectively). Walking distance tests did not improve (4 studies, SMD 0.30, 95% CI -0.01 to 0.62), neither did Visual Analogue Score for breathlessness in two small studies (WMD 3.6, 95% CI -4.6 to 11.8). The relative risk (RR) of nausea was greater with theophylline (RR 7.7; 95% CI 1.5 to 39.9). However, patients' preference for theophylline was greater than that for placebo (RR 2.27; 95% CI 1.26 to 4.11). Very few participants withdrew from these studies for any reason.
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