Criner 1999.

Methods	Prospective, randomised controlled trial. Allows cross‐over of participants from medical to surgical arm after they had completed evaluation after 3 additional months of medical therapy and rehabilitation. Method of randomisation: not described Allocation concealment: unclear Outcome assessor blinding: not described Withdrawals/Dropouts: fully accounted for
Participants	Screened: 200 Randomised: 37 (LVRS 19; control 18) Completed: LVRS 19; control 18 Mean age in years: 59 Diagnosis: CT scan Emphysema: diffuse, heterogeneous, bullae < 5 cm Entry criteria: non‐smokers (≥ 6 months); symptomatic despite optimised medical therapy; NYHA Classes III and IV; evidence of airflow obstruction and hyperinflation by pulmonary function studies (i.e. FEV1 < 30% of predicted, postbronchodilator administration, FRC or TLC > 120% of predicted), hyperinflation documented by chest X‐ray and diffuse bullous emphysema documented by high‐resolution computed tomography (CT) scan, decreased or absent perfusion documented in planned resected lung tissue by quantitative perfusion lung scan Exclusion criteria: severe and refractory hypoxaemia (PaO2/FiO2 ratio < 150); severe hypercapnic respiratory failure requiring mechanical ventilation; presence of significant cardiovascular disease; presence of severe pulmonary hypertension (mean pulmonary artery pressure > 35 mmHg); severe debilitated state with total body weight < 70% of ideal body weight; presence of significant extrapulmonary end‐organ dysfunction expected to limit survival; psychosocial dysfunction; continued smoking Baseline QoL: not reported (SF‐36 was administered to participants but was not reported on) 6‐minute walk in metres (SD): 260 (92) for LVRS vs 273 (90) for control FEV1 in litres (% predicted): 0.69 (28) for LVRS vs 0.72 (29) for control RV in litres (% predicted): 4.9 (253) for LVRS vs 4.4 (230) for control TLC in litres (% predicted): 7.0 (140) for LVRS vs 6.8 (135) for control PaO2: not stated PaCO2 in mmHg: 46.50 for LVRS vs 46.40 for control DLCO in L/min/mmHg (SD): 1.97 (0.6) for LVRS vs 1.9 (0.66) for control
Interventions	LVRS via MS and bilateral stapling resection vs usual medical care (including pulmonary rehabilitation) Pulmonary rehabilitation: 8‐week programme with additional 3 months for participants randomised to control. PR had educational, physical, psychosocial supportive components. All participants had individualised programmes based on exercise test results. Outcomes were assessed after 8 weeks of outpatient pulmonary rehabilitation, and 3 months after additional pulmonary rehabilitation or LVRS.
Outcomes	Lung function (performed according to ATS guidelines); arterial blood gases; Sickness Impact Profile (SIP); mortality
Notes	No funding source was stated.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Described as randomised; no other information available
Allocation concealment (selection bias)	Unclear risk	Information not available
Blinding of participants and personnel (performance bias) All outcomes	High risk	LVRS does not lend itself to blinding.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No mention of blinding for outcome assessors
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Methods of handling missing outcome data from questionnaires (if any) not described
Selective reporting (reporting bias)	High risk	No protocol available. SF‐36 mentioned but not reported on.
Other bias	Low risk	Potential risk of cross‐over effects, but results reported separately. Study authors note: "The crossover design of the study may potentially bias the results toward LVRS because patients on the rehabilitation arm may not be as motivated as patients on the LVRS arm given the often dramatic account of LVRS in the lay press."