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

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.

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]).

LFCT is prolonged in low cardiac output. LFCT is a novel method that may be useful to noninvasively assess cardiac function in HF.