1. An isobolographic analysis of diamorphine and levobupivacaine for epidural analgesia in early labour 
G.A. McLeod, B. Munishankar, M.O. Columb 
British Journal of Anaesthesia 
Volume 98, Issue 4, Pages (April 2007)
DOI: /bja/ael373
Copyright © 2007 British Journal of Anaesthesia Terms and Conditions

2. Fig 1
First phase: patient sequences with MEC (95% CI) are plotted (n = 30 per group). (a) MEC for diamorphine was (122.2–165.3) μg ml−1 (testing interval 12.5 µg ml−1). (b) MEC for levobupivacaine was (0.071–0.095)%w/v (testing interval 0.01%w/v).
British Journal of Anaesthesia  , DOI: ( /bja/ael373)
Copyright © 2007 British Journal of Anaesthesia Terms and Conditions

3. Fig 2
Second phase: patient sequences with MEC (95% CI are plotted (n = 20 per group). (a) MEC for diamorphine with levobupivacaine fixed at 0.044%w/v was 65.5 µg ml−1 (56.8–74.2), γ = 0.99 (testing interval; 7 µg). (b) MEC for levobupivacaine with diamorphine fixed at 70 µg ml−1 was 0.041%w/v (0.037–0.049), γ = 0.98 (testing interval 0.004%w/v). (c) MEC estimates for fixed ratio of diamorphine and levobupivacaine were 69.5 µg ml−1 (60.5–78.5) and 0.044%w/v (0.039–0.049) respectively, γ = 1.02, (testing intervals 7 µg and 0.004%w/v).
British Journal of Anaesthesia  , DOI: ( /bja/ael373)
Copyright © 2007 British Journal of Anaesthesia Terms and Conditions

4. Fig 3
Isobolograms are plotted with isoboles (95% CI error bars) and line of addition with 95% CI. (a) The up-down analysis plot shows the isoboles from the first phase with the three isoboles from the second phase. (b) Probit analysis is used to combine the isoboles from the second phase to give a summarized estimate of the second phase. The overall interaction index γ = 1.00 confirms that addition, not synergy, best categorizes the interaction.
British Journal of Anaesthesia  , DOI: ( /bja/ael373)
Copyright © 2007 British Journal of Anaesthesia Terms and Conditions