Thompson 1992.

Methods	Design: parallel group Randomisation: yes, table of random numbers Blinding: double blind, double dummy Withdrawals: stated
Participants	Setting: community Number eligible: not stated Number enrolled: 31 Number in treatment group: 31 in total in treatment or control groups Number in control group: 31 in total in treatment or control groups Number of withdrawals (treatment/control): 1 withdrawal (unspecified as to which group) Number completing trial (treatment/control): 20/10 Age range: mean age 50.6 yr in intervention group, mean age 47.0 yr in placebo group Sex: 15M, 15F Ethnicity: not stated COPD diagnosis: chronic bronchitis (chronic productive cough for most days of each month for at least 2 consecutive years) Severity of COPD: mean FEV1 72.6% predicted in intervention group, mean FEV1 72.0% predicted in the placebo group Inclusion criteria: current cigarette smoking, airflow obstruction with FEV1/FVC <75%, improvement of FEV1/FVC to not more than 75% with bronchodilator Exclusion criteria: seasonal or episodic dyspnoea, wheezing, atopy, other active lung disease, DLCO <50%, infiltrates on chest xray; use of oral or inhaled steroids or inhaled cromolyn within previous 3 months; carbon dioxide retention; cardiac disease or other contraindication to bronchoscopy Baseline characteristics of treatment/control groups: higher smoking history in intervention group (with similar exhaled carbon monoxide levels)
Interventions	BDP µg, 4 times a day ( µg/d) Placebo 4 times a day metered‐dose inhaler 6 weeks
Outcomes	FEV1 FVC MMEFR PEFR Sputum production Exhaled carbon monoxide levels Bronchoscopy visual bronchitis index Bronchoalveolar lavage cell count and parameter Rescue bronchodilator usage
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "randomised using a table of random numbers"
Allocation concealment (selection bias)	Unclear risk	Information not available
Blinding (performance bias and detection bias) All outcomes	Low risk	Quote: "double blinded"
Incomplete outcome data (attrition bias) All outcomes	Low risk	No withdrawals
Selective reporting (reporting bias)	Low risk	All outcomes reported