Table 3

 Comparison of recovery time of patients receiving 50% nitrous oxide (N2O) and patients given placebo or conventional analgesia

StudyNo of patientsStudy populationPain sourceRecovery time (min)p value
50% N2OControl
Recovery time stated as median (range) unless stated otherwise: *median; †mean (range); ‡median (interquartile range).
50% nitrous oxide v placebo
    Saunders et al, 19942060AdultColonoscopy32*36*Not stated
50% nitrous oxide v conventional medication
    Forbes and Collins, 200022102AdultColonoscopy30 (30–45)60 (30–110)<0.0001
    Notini-Gudmarsson et al, 19961038AdultColonoscopy49 (28–148)83 (29–300)<0.05
    Evans et al, 1995130ChildrenFracture reduction30 (15–60)†83 (60–150)†<0.01
    Saunders et al, 19942059AdultColonoscopy32*60*<0.001
    Lindblom et al, 19942150AdultColonoscopy0 (0–5)‡37.5 (10–75)‡0.0001