title: Non-invasive assessment of cardiac output during exercise in healthy young humans: comparison between Modelflow method and Doppler echocardiography method.
abstract: OBJECTIVE
  The Modelflow method can estimate cardiac output from arterial blood pressure waveforms using a three-element model of aortic input impedance (aortic characteristic impedance, arterial compliance, and systemic vascular resistance). We tested the reliability of a non-invasive cardiac output estimation during submaximal exercise using the Modelflow method from finger arterial pressure waveforms collected by Portapres in healthy young humans.
  
  
  METHODS
  The Doppler echocardiography method was used as a reference method. Sixteen healthy young subjects (nine males and seven females) performed a multi-stage cycle ergometer exercise at an intensity corresponding to 70, 90, 110 and 130% of their individual ventilatory threshold for 2 min each. The simultaneous estimation of cardiac output (15 s averaged data) using the Modelflow and Doppler echocardiography methods was performed at rest and during exercise.
  
  
  CONCLUSIONS
  The Modelflow-estimated cardiac output correlated significantly with the simultaneous estimates by the Doppler method in all subjects (r = 0.87, P < 0.0001) and the SE of estimation was 1.93 L min-1. Correlation coefficients in each subject ranged from 0.91 to 0.98. Although the Modelflow method overestimated cardiac output, the errors between two estimates were not significantly different among the exercise levels. These results suggest that the Modelflow method using Portapres could provide a reliable estimation of the relative change in cardiac output non-invasively and continuously during submaximal exercise in healthy young humans, at least in terms of the relative changes in cardiac output.
authors.affiliation: Institute for Human Science and Biomedical Engineering, National Institute of Advanced Industrial Science and Technology (AIST), Namiki, Tsukuba, Ibaraki, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Sugawara
authors.forename: T
authors.initials: T
authors.lastname: Tanabe
authors.forename: M
authors.initials: M
authors.lastname: Miyachi
authors.forename: K
authors.initials: K
authors.lastname: Yamamoto
authors.forename: K
authors.initials: K
authors.lastname: Takahashi
authors.forename: M
authors.initials: M
authors.lastname: Iemitsu
authors.forename: T
authors.initials: T
authors.lastname: Otsuki
authors.forename: S
authors.initials: S
authors.lastname: Homma
authors.forename: S
authors.initials: S
authors.lastname: Maeda
authors.forename: R
authors.initials: R
authors.lastname: Ajisaka
authors.forename: M
authors.initials: M
authors.lastname: Matsuda
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D001795:Blood Pressure Determination / Q000379:methods; D002302:Cardiac Output / Q000502:physiology*; D002307:Cardiography, Impedance; D015150:Echocardiography, Doppler / Q000379:methods*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods; D005260:Female; D006334:Heart Function Tests / Q000379:methods*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D012044:Regression Analysis; D012146:Rest / Q000502:physiology