Ventilation-perfusion relationships with high cardiac output in lobar atelectasis

P. T. Schumacker, J. C. Newell, T. M. Saba, S. R. Powers

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Pulmonary gas exchange was evaluated in 10 anesthetized mechanically ventilated dogs. Cardiac output (QT) was increased approximately 50% by opening peripheral arteriovenous fistulas. With both lungs ventilated, increasing QT increased mixed venous O2 pressure (PO2) and pulmonary arterial pressure, but neither shunt fraction nor the distribution of ventilation-perfusion was consistently altered. During left lung atelectasis, increasing QT again increased mixed venous PO2 and pulmonary arterial pressure, but two different responses in shunt-like perfusion were measured. In 4 dogs, left lung atelectasis caused a shunt fraction of 46 ± 6% that was not changed by high QT (P > 0.05). In 6 dogs, atelectasis caused a shunt fraction of 24 ± 3% during normal QT that increased to 42 ± 2% during high QT (P < 0.001). Dogs whose shunt fraction during atelectasis was high and unchanged by QT had lower arterial pH (7.24 ± 0.03) than dogs whose shunt fraction was initially lower and was increased with QT (7.36 ± 0.02) (P < 0.01). We conclude that increased QT can worsen shunt flow during lobar atelectasis when hypoxic vasoconstriction has been effective in limiting perfusion to the collapsed region at normal levels of QT.

Original languageEnglish (US)
Pages (from-to)341-347
Number of pages7
JournalJournal of Applied Physiology Respiratory Environmental and Exercise Physiology
Issue number2
StatePublished - 1981

ASJC Scopus subject areas

  • Physiology
  • Endocrinology


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