Pulse contour cardiac output derived from non‐invasive arterial pressure in cardiovascular disease

Pulse contour methods determine cardiac output semi‐invasively using standard arterial access. This study assessed whether cardiac output can be determined non‐invasively by replacing the intra‐arterial pressure input with a non‐invasive finger arterial pressure input in two methods, Nexfin CO‐trek® and Modelflow®, in 25 awake patients after coronary artery bypass surgery. Pulmonary artery thermodilution cardiac output served as a reference. In the supine position, the mean (SD) differences between thermodilution cardiac output and Nexfin CO‐trek were 0.22 (0.77) and 0.44 (0.81) l.min−1, for intra‐arterial and non‐invasive pressures, respectively. For Modelflow, these differences were 0.70 (1.08) and 1.80 (1.59) l.min−1, respectively. Similarly, in the sitting position, differences between thermodilution cardiac output and Nexfin CO‐trek were 0.16 (0.78) and 0.34 (0.83), for intra‐arterial and non‐invasive arterial pressure, respectively. For Modelflow, these differences were 0.58 (1.11) and 1.52 (1.54) l.min−1, respectively. Thus, Nexfin CO‐trek readings were not different from thermodilution cardiac output, for both invasive and non‐invasive inputs. However, Modelflow readings differed greatly from thermodilution when using non‐invasive arterial pressure input.