Fig. 3. Acetylcholine dose–response curves. All data are represented as mean ± SEM. A , Similar dose–response curves to acetylcholine for the first and the second measurement in controls. (P = 0.59). B , I/R of the forearm significantly blunted dose-dependent response to acetylcholine (P = 0.001), indicating postischemic endothelial dysfunction. Helium early (C , P = 0.581) and late preconditioning (D , P = 0.165) prevented postischemic endothelial dysfunction, as did ischemic preconditioning (E , P = 0.657). controls = control group without ischemia; FAV = forearm volume; He-EPC = helium early preconditioning group; He-LPC = helium late preconditioning group; I/R = ischemia-reperfusion group; IPC = Ischemic preconditioning group.