Wong 1987.

Methods	Randomised blind cross over controlled trial.
Participants	11 men, 4 women. Mean age 28 years.
Interventions	Nitroglycerin 0.4 mg s.l. and normal saline 0.25ml s.c.
Outcomes	LOS pressure; radiolabelled test meal of oesophageal retention.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Unclear risk	Quote: On four separate days, participants received one of four medications "in a random order".
Allocation concealment?	High risk	The four medications were given by different way, either s.l., s.c., or i.v.
Blinding? clinical response	Unclear risk	Did not report clinical response for every participant.
Blinding? Manometric examinations	Low risk	Quote: "After studying 15 participants, recordings of individual station pull‐throughs were removed from the entire tracing, coded, randomised, and read by a single un‐informed observer."
Incomplete outcome data addressed? All outcomes	Low risk	Yes
Free of selective reporting?	Unclear risk	Did not report clinical response for every participant.
Free of other bias?	Low risk	Yes

i.v. intravenous

s.l. sub lingual

s.c. sub cutaneous