- At the times N1, N2, and N3, the average NT-proBNP level in the group of patients with low cardiac output (CI <2.4 l / min / m2; CO <4.0 l / min) was higher than that in the group with normal cardiac output (CI ≥ 2.4 l / min / m2; CO ≥ 4.0 l / min), the difference was statistically significant with p <0.05.