Direct measurement of nitrous oxide kinetics† G.B. Drummond, L Fisher, O Pumphrey, R.R. Kennedy  British Journal of Anaesthesia  Volume 109, Issue 5, Pages 776-781 (November 2012) DOI: 10.1093/bja/aes260 Copyright © 2012 The Author(s) Terms and Conditions

Fig 1 Time plan of the study. Each test period consisted of a 30 min period of mask breathing, separated into 10 min of air breathing, test gas for 10 min, and then reversion to air. Two practice DSSTs were done for 40 s, separated by 20 s, at the start of air breathing. Two further tests for baseline measurements were done starting 2.5 min before switching to the test gas and then tests were repeated at 1 min intervals for 5 min after the gas change occurred. A similar plan was used for the switch back to air. British Journal of Anaesthesia 2012 109, 776-781DOI: (10.1093/bja/aes260) Copyright © 2012 The Author(s) Terms and Conditions

Fig 2 Plots of the mean DSST result against predicted central concentrations, using T1/2 values of 12.5, 25, 50, and 75 s. Bars indicate 95% CI of the mean. The arrow indicates the direction of the loop. The bottom panel shows the area of the loop (solid line) (using a convention that a loop showing an anticlockwise time progress would be positive) is related to the T1/2 values used for the predictions, and fitted with a quadratic (r2 = 1). The zero intercept is at a T1/2 of 37 s. British Journal of Anaesthesia 2012 109, 776-781DOI: (10.1093/bja/aes260) Copyright © 2012 The Author(s) Terms and Conditions