title: A Novel Method for Assessing Cardiac Output With the Use of Oxygen Circulation Time.
abstract: 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.
  
  
  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 O2desaturation, was correlated with cardiac output. Among 48 subjects recruited, 37 manifested ≥3% O2desaturation 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.
authors.affiliation: Department of Medicine, Cardiovascular Division, University of Minnesota Medical School, Minneapolis, Minnesota. Electronic address: kwonx208@umn.edu.
authors.forename: Younghoon
authors.initials: Y
authors.lastname: Kwon
authors.affiliation: Department of Medicine, Cardiovascular Division, University of Minnesota Medical School, Minneapolis, Minnesota.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Van't Hof
authors.affiliation: Department of Medicine, Cardiovascular Division, University of Minnesota Medical School, Minneapolis, Minnesota.
authors.forename: Samit S
authors.initials: SS
authors.lastname: Roy
authors.affiliation: Department of Medicine, Cardiovascular Division, University of Minnesota Medical School, Minneapolis, Minnesota.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Bache
authors.affiliation: Department of Medicine, Cardiovascular Division, University of Minnesota Medical School, Minneapolis, Minnesota.
authors.forename: Gladwin
authors.initials: G
authors.lastname: Das
mesh_terms: D000368:Aged; D001776:Blood Circulation Time / Q000379:methods; D001783:Blood Flow Velocity / Q000502:physiology; D006328:Cardiac Catheterization / Q000379:methods*; D002302:Cardiac Output / Q000502:physiology*; D015331:Cohort Studies; D005260:Female; D006333:Heart Failure / Q000175:diagnosis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology*; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D013815:Thermodilution / Q000379:methods
keywords: Cardiac output; circulation; circulation time; heart failure