title: Noninvasive methods for determining pulmonary vascular function in children with pulmonary arterial hypertension: application of a mechanical oscillator model.
abstract: OBJECTIVE
  Noninvasive diagnostics for pulmonary arterial hypertension (PAH) have traditionally sought to predict main pulmonary artery pressure from qualitative or direct quantitative measures of the flow velocity pattern obtained from spectral Doppler ultrasound examination of the main pulmonary artery. A more detailed quantification of flow velocity patterns in the systemic circuit has been obtained by parameterizing the flow trace with a simple dynamic system model. Here, we investigate such a model's utility as a noninvasive predictor of total right heart afterload and right heart function.
  
  
  METHODS
  Flow velocity and pressure was measured within the main pulmonary artery during right heart catheterization of patients with normal hemodynamics (19 subjects, 20 conditions) and those with PAH undergoing reactivity evaluation (34 patients, 69 conditions). Our model parameters were obtained by least-squares fitting the model velocity to the measured flow velocity.
  
  
  RESULTS
  Five parameter means displayed significant (P < .05) differences between normotensive and hypertensive groups. The model stiffness parameter correlated to actual pulmonary vascular resistance (r = 0.4924), pulmonary vascular stiffness (r = 0.6811), pulmonary flow (r = 0.6963), and stroke work (r = 0.7017), while the model initial displacement parameter had good correlation to stiffness (r = 0.6943) and flow (r = 0.6958).
  
  
  CONCLUSIONS
  As predictors of total right heart afterload (resistance and stiffness) and right ventricle work, the model parameters of stiffness and initial displacement offer more comprehensive measures of the disease state than previous noninvasive methods and may be useful in routine diagnostic monitoring of patients with PAH.
authors.affiliation: Center for Bioengineering, University of Colorado Health Science Center, Denver, CO 80045, USA. Hunterk@colorado.edu
authors.forename: Kendall S
authors.initials: KS
authors.lastname: Hunter
authors.forename: Justin K
authors.initials: JK
authors.lastname: Gross
authors.forename: Craig J
authors.initials: CJ
authors.lastname: Lanning
authors.forename: K Scott
authors.initials: KS
authors.lastname: Kirby
authors.forename: Karrie L
authors.initials: KL
authors.lastname: Dyer
authors.forename: D Dunbar
authors.initials: DD
authors.lastname: Ivy
authors.forename: Robin
authors.initials: R
authors.lastname: Shandas
mesh_terms: D000293:Adolescent; D001795:Blood Pressure Determination / Q000379:methods* / Q000592:standards*; D006328:Cardiac Catheterization; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000175:diagnosis* / Q000503:physiopathology*; D007223:Infant; D008297:Male; D008955:Models, Cardiovascular; D010865:Pilot Projects; D011651:Pulmonary Artery / Q000000981:diagnostic imaging / Q000503:physiopathology*; D012015:Reference Standards; D015203:Reproducibility of Results; D018608:Ultrasonography, Doppler; D014655:Vascular Resistance