Kao 1983.

Methods	Blinding of randomization: not mentioned ‐ 'random sequence' Blinding of intervention: not mentioned Complete follow up: yes Blinding of outcome: not mentioned Randomized controlled trial, cross‐over design with pooled data Washout period: 48 hours before study, 48 hours at cross‐over
Participants	Patients entered into the study: n=10 No mechanical ventilation Entry criteria: gestational age < 34 weeks, history of RDS (typical chest radiograph, need for >40% O2, need for CPAP or mechanical ventilation), continued requirement for mechanical ventilation and 30% FiO2 at 30 days of age, radiographic evidence of stage 3 or 4 of BPD by one month of age. Exclusion criteria: patent ductus arteriosus, mechanical ventilation. Ten patients were included into the study. Mean birth weight was 1.37±0.63 kg, gestational age 30.0±3.2 weeks, average postnatal age 11 weeks, postconceptional age 41.0±3.2 weeks and weight 2.28±0.38 kg. There was no difference between furosemide and placebo periods in baseline values of lung volume and resistance. Baseline values for compliance tended to be 27% lower during the furosemide period than during the placebo period, and those for conductance were 26 % lower (p<0.05 by unpaired Student t‐test).
Interventions	Furosemide vs placebo Patients were randomly allocated, either to receive 1 dose of furosemide 1 mg/kg iv followed after 48 hours by placebo (10% glucose in water), or vice versa. Fluid intake was similar on furosemide and on placebo (175.4±38.0 vs 175.5±30.4 ml/kg/day).
Outcomes	No changes in urine output or pulmonary function occurred versus baseline after placebo administration. Furosemide resulted in a significantly higher increase than placebo for urine output during the first period (0‐1 hr, +226±85% vs ‐9±49%, respectively, p<0.001) and the second period (1‐3 hr, +58±74% vs 0±22%, p<0.05). Furosemide administration resulted in a significantly better improvement than placebo for the following variables: compliance at 1 hour (+54±41% vs +2±5% with placebo, p<0.01), airway conductance both at 1/2 hour (+54±52% vs ‐18±6% with placebo, p<0.001) and at 1 hour (+84±70% vs +3±8% with placebo, p<0.01) and resistance at 1/2 hour (‐30±37% vs +2±3%, p<0.05) and at 1 hour (‐35±41% vs ‐5±3%, p<0.05. The authors state there was no significant change in thoracic gas volume; data are not provided.
Notes	Measurements of pulmonary function and urine were obtained at 1/2, 1,2,4,6 and 24 hours after medication administration. Patients were lightly sedated with chloral hydrate (5‐10 mg/kg). The authors measured airway resistance by plethysmography and dynamic compliance using an esophageal balloon. Urine output was measured over the following periods: 0‐1, 1‐3,3‐6,6‐16 and 16‐24 hours. Values are presented as % of baseline. Some values of pulmonary function measurements calculated from the figures were overridden to match those in the text.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomized controlled trial, cross‐over design with pooled data Blinding of randomization: not mentioned ‐ 'random sequence'
Allocation concealment (selection bias)	Unclear risk	Blinding of randomization: not mentioned ‐ 'random sequence'
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Blinding of intervention: not mentioned Blinding of outcome: not mentioned
Incomplete outcome data (attrition bias) All outcomes	Low risk	Complete follow up: yes