Figure 7. (A) shows PVA-independent VO2-Emax relations during control-calcium (open circles and dotted line; PVA-independent VO2= 3.51 x 10 sup -3 Emax + 0.0138, r = 0.965) and isoflurane-calcium inotropism run (closed circles and solid line, PVA-independent VO2= 3.99 x 10 sup -3 Emax + 0.0129, r = 0.992) in the same heart as Figure 4. Linear regression lines for the control-calcium and isoflurane-calcium inotropism runs are almost superimposable. The slope of the lines indicates the oxygen cost of Emax. (B) compares mean values of the oxygen cost of Emax in the calcium inotropism runs in control and at 2.0% isoflurane. NS, not significant. Vertical bars indicate standard deviation. Maximal calcium concentration was 1.4 mM.