Table 2.

Patterns and amounts of N₂O used by patients

	London	Birmingham	Manchester	Total
Number with documented N2O use	56	35	28	119
Number with documented amount of use	51 (91%)	14 (40%)	13 (46%)	78 (65.5%)
Median weekly N2O amount in 8 g canisters	560	200	75	318
Range weekly N2O amount in 8 g canisters	5 to 2800	21 to 2100	1 to 1680	1 to 2800
Individuals with documented use of larger ~600 g cylinders	10 (17.9%)	7 (20%)	3 (10.7%)	20 (16.8%)
Median weekly larger N2O cylinder amount	10	3	1	7
Range weekly larger N2O cylinder amount	1 to 35	1 to 28	1 to 13	1 to 35
N2O use pattern (regular/sporadic/unknown)	43/9/4 (77%/16%/7%)	29/4/2 (83%/11%/6%)	19/1/8 (68%/3%/29%)	91/14/14 (76%/12%/12%)

Values are displayed as the number in relation to each column, displaying N₂O use across hospitals in these cities. Where relevant, percentages of that value of the total for that column are given in parentheses. Where documented, consumed amounts of N₂O taken from electronic patient records enabled classification of use amounts and patterns of use. One large ~600 g N₂O cylinder was taken to be equivalent to 75 of the smaller ~8 g canisters and incorporated into the median 8 g canister amount.

N₂O, nitrous oxide.