Compared to salmeterol, 50 μg what was the result of tiotropium 18 μg once daily  on forced vital capacity (FVC)?
After 169 days of treatment, the mean ± SE improvement above placebo in trough FEV1 was 110 ± 20 mL for tiotropium (p < 0.001) and 80 ± 20 mL for salmeterol (p < 0.001) (Table 3a).