title: Noninvasive cardiac output measurement by inert gas rebreathing in suspected pulmonary hypertension.
abstract: The objective of this study was to evaluate inert gas rebreathing (IGR) reliability in cardiac output (CO) measurement compared with Fick method and thermodilution. IGR is a noninvasive method for CO measurement; CO by IGR is calculated as pulmonary blood flow plus intrapulmonary shunt. IGR may be ideal for follow-up of patients with pulmonary hypertension (PH), sparing the need of repeated invasive right-sided cardiac catheterization. Right-sided cardiac catheterization with CO measurement by thermodilution, Fick method, and IGR was performed in 125 patients with possible PH by echocardiography. Patients were grouped according to right-sided cardiac catheterization-measured mean pulmonary and wedge pressures: normal pulmonary arterial pressure (n = 20, mean pulmonary arterial pressure = 18 ± 3 mm Hg, pulmonary capillary wedge pressure = 11 ± 5 mm Hg), PH and normal pulmonary capillary wedge pressure (PH-NW, n = 37 mean pulmonary arterial pressure = 42 ± 13 mm Hg, pulmonary capillary wedge pressure = 11 ± 6 mm Hg), and PH and high pulmonary capillary wedge pressure (PH-HW, n = 68, mean pulmonary arterial pressure = 37 ± 9 mm Hg, pulmonary capillary wedge pressure = 24 ± 6 mm Hg). Thermodilution and Fick measurements were comparable. Fick and IGR agreement was observed in normal pulmonary arterial pressure (CO = 4.10 ± 1.14 and 4.08 ± 0.97 L/min, respectively), whereas IGR overestimated Fick in patients with PH-NW and those with PH-HW because of intrapulmonary shunting overestimation in hypoxemic patients. When patients with arterial oxygen saturation (SO2) ≤90% were excluded, IGR and Fick agreement improved in PH-NW (CO = 4.90 ± 1.70 and 4.76 ± 1.35 L/min, respectively) and PH-HW (CO = 4.05 ± 1.04 and 4.10 ± 1.17 L/min, respectively). In hypoxemic patients, we estimated pulmonary shunt as Fick - pulmonary blood flow and calculated shunt as: -0.2423 × arterial SO2 + 21.373 L/min. In conclusion, IGR is reliable for CO measurement in patients with PH with arterial SO2 >90%. For patients with arterial SO2 ≤90%, a new formula for shunt calculation is proposed.
authors: Centro Cardiologico Monzino, IRCCS, Milan, Italy.
authors: Stefania
authors: S
authors: Farina
authors: Centro Cardiologico Monzino, IRCCS, Milan, Italy.
authors: Giovanni
authors: G
authors: Teruzzi
authors: Centro Cardiologico Monzino, IRCCS, Milan, Italy.
authors: Gaia
authors: G
authors: Cattadori
authors: Centro Cardiologico Monzino, IRCCS, Milan, Italy.
authors: Cristina
authors: C
authors: Ferrari
authors: Centro Cardiologico Monzino, IRCCS, Milan, Italy.
authors: Stefano
authors: S
authors: De Martini
authors: Cardiologia Riabilitativa, Fondazione S. Maugeri, IRCCS, Milan, Italy.
authors: Maurizio
authors: M
authors: Bussotti
authors: Centro Cardiologico Monzino, IRCCS, Milan, Italy.
authors: Giuseppe
authors: G
authors: Calligaris
authors: Centro Cardiologico Monzino, IRCCS, Milan, Italy; Cardiovascular Section, Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy.
authors: Antonio
authors: A
authors: Bartorelli
authors: Centro Cardiologico Monzino, IRCCS, Milan, Italy; Cardiovascular Section, Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy; Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Washington, Seattle, Washington. Electronic address: piergiuseppe.agostoni@ccfm.it.
authors: Piergiuseppe
authors: P
authors: Agostoni
mesh_terms: D000368:Aged; D001944:Breath Tests / Q000379:methods*; D002302:Cardiac Output / Q000502:physiology*; D004452:Echocardiography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006976:Hypertension, Pulmonary / Q000175:diagnosis / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011669:Pulmonary Wedge Pressure / Q000502:physiology*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012720:Severity of Illness Index