| Author, date and country | Patient group | Study type (level of evidence) | Outcomes | Key results | Study weaknesses |
|---|---|---|---|---|---|
| Turner MO et al, Canada, 1997 | 12 of 18 randomised trials (507 patients) | Meta-analysis | Effect size | −0.02 (−0.2 to 0.16) | Includes 102 patients with COPD |
| Cates C and Rowe BH, UK, 2001 | 7 of 44 randomised trials (375 patients) | Systematic review | FEV1 | No significant difference | |
| PEFR | No significant difference | ||||
| Length of stay | No significant difference |