A Novel Method for Assessing Cardiac Output With the Use of Oxygen Circulation Time

Background We investigated whether a simple breath hold would yield dynamic oxygen (O₂) saturation change and whether the derived circulation time would be useful in assessing cardiac function. Methods and Results Patients undergoing right heart catheterization for clinical indications (n = 48), including heart failure (HF; n = 24), were prospectively recruited. Each subject was instructed to hold their breath for 20–40 seconds. Lung to finger circulation time (LFCT), defined as the time from the point of rebreathing to nadir O₂ desaturation, was correlated with cardiac output. Among 48 subjects recruited, 37 manifested ≥3% O₂ desaturation allowing for an LFCT measurement. Mean LFCT was 38.5 ± 17.5 seconds (range 18.9–94.7 s). LFCT in patients with a clinical diagnosis of HF was significantly longer than those without (45.9 ± 19.9 s vs 31.5 ± 11.5 s; P = .01). Overall, the LFCT was inversely correlated with cardiac output (Fick: r = −0.56; P < .001 [n = 37]; thermodilution: r = −0.6; P = .001 [n = 27]). Conclusions LFCT is prolonged in low cardiac output. LFCT is a novel method that may be useful to noninvasively assess cardiac function in HF.