Chua 2004.

Study characteristics
Methods	Parallel, randomiSed controlled trial
Participants	Setting: recruited from Singapore General Hospital, Singapore Sample size: N = 42 Participants: age not provided Inclusion criteria: ASA physical status I nulliparous women in early spontaneous labour pain with at least one contraction every 5 min who had requested neuraxial block
Interventions	AMB (n = 21): ropivacaine 0.1% plus fentanyl 2 µg/mL for maintaining epidural analgesia The initial 5 mL bolus was administered 30 min after time 0, followed by 5 mL boluses every hour thereafter. As the highest rate of delivery afforded by the pump was 100 mL/h, each epidural bolus was delivered over 3 min. BI (n = 21): ropivacaine 0.1% plus fentanyl 2 µg/mL for maintaining epidural analgesia. A rate of 5 mL/h was initiated 1 min after time 0 by using a Terumo syringe pump
Outcomes	Rate of breakthrough pain with need for anaesthetic intervention LA consumption per hour
Notes	Study dates not stated Funding sources not declared No conflict of interests declared
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Method of randomisation not stated: Quote: "The parturients were then randomly assigned by the blind opaque envelope technique to receive either epidural CIB (n = 21) or CEI (n = 21)"
Allocation concealment (selection bias)	Low risk	Allocation by sealed opaque envelopes: Quote:"The parturients were then randomly assigned by the blind opaque envelope technique to receive either epidural CIB (n = 21) or CEI (n = 21)"
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Epidurals were performed by the principal investigator: Quote:"All blocks performed by the principal investigator (S.M.H.C.)"  Blinding of epidural pump settings to participants were not specified.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	It was not stated if participants were blinded. Quote:"All data was collected by an anaesthesiologist who was not involved in instituting the block"
Incomplete outcome data (attrition bias) All outcomes	Low risk	No dropouts
Selective reporting (reporting bias)	Low risk	All a priori outcomes reported based on published protocol
Other bias	Low risk	Sample size was computed to detect a 30‐min difference (α = 0.05, ß = 0.2) in the duration of analgesia