A new method for noninvasive bedside determination of pulmonary blood flow
- Cite this article as:
- Gedeon, A., Forslund, L., Hedenstierna, G. et al. Med. Biol. Eng. Comput. (1980) 18: 411. doi:10.1007/BF02443310
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A method is presented for determining the pulmonary blood flow from measurements of the time-averaged end-tidal pCO2 and the CO2 output.
The novel technique is based on a formula that is derived from Fick's principle in such a way that it allows a direct calculation of the lung perfusion from simultaneously measured changes in end-tidal pCO2 and CO2 output.
These changes are induced by altering the ventilation pattern of the patient for short (30s) periods of time. Different ways of doing this are discussed and it is shown that a bidirectional change in ventilation, involving hyper- and hypoventilation patterns, most adequately corresponds to the formula derived.
The method has been validated by comparison with cardiac output data obtained by thermodilution. Forty-two measurements were performed during mechanical ventilation on five dogs and six patients with essentially healthy lungs. Lung perfusion was in the range 0·4–6·5l/min. We found that QCO2=0·97 Qthermo with a s.d.=18%. The reproducibility of individual measurements was better than 0·3l/min.