Sources of error in noninvasive pulmonary blood flow measurements by partial rebreathing: A computer model study

Johnny S. Yem, Yongquan Tang, Martin J. Turner*, A. Barry Baker

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)


Background: Partial rebreathing is a noninvasive method for measuring pulmonary blood flow (PBF). This study examines the systematic errors produced by the partial rebreathing technique utilizing a comprehensive mathematical model of the cardiorespiratory system of a healthy, 70-kg adult male. Methods: The model simulates tidal breathing through a branched respiratory tree and incorporates the effects on carbon dioxide dynamics of lung tissue mass, vascular transport delays, multiple body compartments, and realistic blood-gas dissociation curves. Four studies were performed: (1) errors produced under standard conditions, (2) effects of recirculation, (3) effects of alveolar-proximal airway partial pressure of carbon dioxide (Pco2) differences, and (4) effects of rebreathing time. Results: Systematic errors are less than 10% when the simulated PBF is between 3 and 6 l/min. At 2 l/min, PBF is overestimated by approximately 35%. At 14 l/min, PBF is underestimated by approximately 40%. At PBF of greater than 6 l/min, recirculation causes approximately 60% of the systematic error, alveolar-proximal airway differences cause approximately 20%, and alveolar-arterial differences cause approximately 20%. The standard rebreathing time of 50 s is shown to be excessive for PBF of greater than 6 l/min. At PBF of less than 3 l/min, errors are caused by inadequate rebreathing time and alveolar-arterial gradients. Conclusions: Systematic errors in partial rebreathing cardiac output measurements have multiple causes. Our simulations suggest that errors can be reduced by using a variable rebreathing time, which should be increased at low PBF so that quasiequilibrium in the alveoli can be achieved and decreased at high PBF to reduce the effects of recirculation.

Original languageEnglish
Pages (from-to)881-887
Number of pages7
Issue number4
Publication statusPublished - 1 Apr 2003
Externally publishedYes


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