A noninvasive method for estimating cardiac output using lung to finger circulation time of oxygen.

To develop a safe, noninvasive, simple, inexpensive, and clinically adaptable method for estimating cardiac output, we evaluated the potential of lung to finger circulation time (LFCT) and buildup time (Tb) of oxygen as measured by pulse oximetry to estimate cardiac output. Significant correlation was found between cardiac output as measured by thermodilution and the inverse of LFCT (R = 0.76, p < 0.001, SEE = 0.9 L/min) as well as the inverse of Tb (R = 0.72, p < 0.001, SEE = 0.9 L/min).