title: Noninvasive cardiac output estimation by inert gas rebreathing in pediatric and congenital heart disease.
abstract: BACKGROUND
  Inert gas rebreathing (IGR) techniques provide rapid, reliable estimates of cardiac output in adults with structurally normal hearts. Data on IGR reliability in pediatric and congenital heart disease populations are lacking. Our objective was to validate pulmonary blood flow (Qp) measurement by IGR compared with clinical reference tests, cardiovascular magnetic resonance (CMR), and indirect Fick.
  
  
  METHODS
  Pulmonary blood flow was measured by IGR and CMR or indirect Fick in 80 patients grouped by presence and type of shunt lesion. Inert gas rebreathing precision was assessed using Bland-Altman analysis, repeatability coefficient, intraclass correlation, and coefficient of error. Agreement with the reference tests was assessed with Bland-Altman plots. For comparison, agreement between the 2 reference tests, CMR and indirect Fick, was assessed in 34 contemporary patients.
  
  
  RESULTS
  Subjects were aged 7-78 years and had a wide range of cardiac diagnoses. Inert gas rebreathing Qp showed good repeatability (95% limits of agreement for 2 trials = ±22%, repeatability coefficient = 1.2 L/min, intraclass correlation = 0.92, and coefficient of error = 5%). In the absence of left-to-right shunting (n = 67), IGR Qp estimates agreed with CMR and indirect Fick Qp estimates, and the reference tests agreed with each other, with mean bias ≤10% (≤0.5 L/min) and 95% limits of agreement ±33%-38%. Conversely, IGR was unreliable in patients with left-to-right shunt (n = 14), with large bias (-58%, -4.0 L/min) and wide limits of agreement (±76%).
  
  
  CONCLUSIONS
  Inert gas rebreathing reliably estimates Qp in children and adults with congenital heart disease in the absence of left-to-right shunting, with agreement comparable to that seen between CMR and indirect Fick estimates.
authors.affiliation: Department of Cardiology, Boston Children's Hospital, Boston, MA.
authors.forename: Amanda K
authors.initials: AK
authors.lastname: Marma
authors.affiliation: Department of Cardiology, Boston Children's Hospital, Boston, MA; Division of Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital, Boston, MA. Electronic address: Alexander.Opotowsky@cardio.chboston.org.
authors.forename: Alexander R
authors.initials: AR
authors.lastname: Opotowsky
authors.affiliation: Department of Cardiology, Boston Children's Hospital, Boston, MA.
authors.forename: Brian S
authors.initials: BS
authors.lastname: Fromm
authors.affiliation: Department of Cardiology, Boston Children's Hospital, Boston, MA; Department of Cardiovascular Surgery, Boston Children's Hospital, Boston, MA.
authors.forename: Ana
authors.initials: A
authors.lastname: Ubeda-Tikkanen
authors.affiliation: Department of Cardiology, Boston Children's Hospital, Boston, MA.
authors.forename: Diego
authors.initials: D
authors.lastname: Porras
authors.affiliation: Department of Cardiology, Boston Children's Hospital, Boston, MA. Electronic address: Jonathan.Rhodes@cardio.chboston.org.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Rhodes
mesh_terms: D000280:Administration, Inhalation; D000293:Adolescent; D000328:Adult; D000368:Aged; D006328:Cardiac Catheterization; D002302:Cardiac Output / Q000502:physiology*; D002648:Child; D004452:Echocardiography; D005260:Female; D006330:Heart Defects, Congenital / Q000175:diagnosis / Q000378:metabolism / Q000503:physiopathology*; D006801:Humans; D001239:Inhalation; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D008875:Middle Aged; D005741:Noble Gases / Q000008:administration & dosage*; D011379:Prognosis; D015203:Reproducibility of Results; D012189:Retrospective Studies; D016276:Ventricular Function / Q000502:physiology*; D055815:Young Adult
chemical_list: D005741:Noble Gases