Figure 5.

Mean plasma potassium concentration and mean Q-Tc 30 min after each subdivided dose fraction vs. the cumulative number of doubling doses (2 doubling doses implies 2² = 4 inhalations, 2.585 doubling doses 2^2.585 = 6 inhalations, 3 doubling doses 2³ = 8 inhalations, and 3.22 doubling doses 2^3.22 = 10 inhalations). Dotted lines indicate the required number of doubling formoterol doses to match 2 doubling doses (2000 µg) of terbutaline; the solid line, parallel to the x-axis, indicates the 95% confidence interval for the estimate. Dose fractions of formoterol were 18 + 9 + 9 + 9 µg (filled circles), and dose fractions of terbutaline were 2000 + 1000 + 1000 + 1000 µg (open circles)