Rao 2011.

Methods	Randomised, double‐blind placebo‐controlled trial 12 weeks duration
Participants	Inclusion criteria: Ambulatory participants Severe or very severe COPD (according to Global Initiative for Chronic Obstructive Lung Disease (GOLD) classification) Past history of smoking of at least 20 pack years PASP > 40 mmHg as measured by Doppler echocardiography Exclusion criteria: An acute exacerbation of COPD in last month History of bronchial asthma or > 12% increase in FEV1 with bronchodilator History of primary cardiac disease or documented IHD Use of nitrates or other vasodilator throughout the study period Haemoglobin < 12 g/dL Any severe concomitant disease Evidence of PAH due to any other cause, such as pulmonary thromboembolism, HIV, scleroderma, congenital heart disease and de‐compensated right or left heart failure. (WHO Group 3) n = 37
Interventions	Oral sildenafil 20 mg 3 times a day (N=17) compared to identical placebo (N=20)
Outcomes	Primary outcome: change in 6MWD. Improvement in PAP was taken as secondary outcome of the study
Notes	Industry provided the drugs. No other funding source stated Trial conducted at SMS Medical College and Hospital, Jaipur (Rajasthan), India (dates of recruitment not stated)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Sildenafil and placebo were dispensed according to random allocation of computer‐generated code
Allocation concealment (selection bias)	Low risk	Drug was dispensed by an unblinded co‐ordinator, who dispensed the drug to blinded co‐ordinator, who gave it to the participants
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Drug was dispensed by an unblinded co‐ordinator, who dispensed the drug to blinded co‐ordinator, who gave it to the participants
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not explicitly stated
Incomplete outcome data (attrition bias) All outcomes	Low risk	Withdrawals were accounted for and similar across the 2 groups ‐ where in each group 1 was lost to follow‐up, 1e in the sildenafil group had an acute exacerbation, and 1 in the placebo group withdrew consent
Selective reporting (reporting bias)	Low risk	Prespecified outcomes were reported
Other bias	Low risk	Other risk of bias is unlikely