Table 3

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

Study	No of patients	Study population	Pain source	Recovery time (min)		p value
Study	No of patients	Study population	Pain source	50% N₂O	Control	p value
Recovery time stated as median (range) unless stated otherwise: *median; †mean (range); ‡median (interquartile range).
50% nitrous oxide v placebo
Saunders et al, 1994²⁰	60	Adult	Colonoscopy	32*	36*	Not stated
50% nitrous oxide v conventional medication
Forbes and Collins, 2000²²	102	Adult	Colonoscopy	30 (30–45)	60 (30–110)	<0.0001
Notini-Gudmarsson et al, 1996¹⁰	38	Adult	Colonoscopy	49 (28–148)	83 (29–300)	<0.05
Evans et al, 1995¹	30	Children	Fracture reduction	30 (15–60)†	83 (60–150)†	<0.01
Saunders et al, 1994²⁰	59	Adult	Colonoscopy	32*	60*	<0.001
Lindblom et al, 1994²¹	50	Adult	Colonoscopy	0 (0–5)‡	37.5 (10–75)‡	0.0001