Effects of altered patterns of ventilation and of increased cardiac output on blood flow to a collapsed lung in anaesthetized, closed-chest dogs
Niblett, D.J.; Cannon, D.; Sykes, M.K.
British Journal of Anaesthesia 60(2): 198-206
1988
ISSN/ISBN: 0007-0912 PMID: 3278727 Document Number: 314635
Right-to-left shunt (.ovrhdot.Qs/.ovrhdot.Qt) was measured by the SF6 and oxygen methods in 13 anaesthetized closed-chest dogs intubated with a double-lumen endobronchial tube. Collapse of the left lung increased .ovrhdot.Qs/.ovrhdot.Qt from 10% to 23%, suggesting that blood flow to the left lung had been reduced by about 60%. Increasing right lung mean airway pressure by the alteration of the inspiratory:expiratory time ratio or the application of PEEP produced a small but non-significant increase in .ovrhdot.Qs/.ovrhdot.Qt with significant increases in arterial and mixed venous carbon dioxide tensions, and arterial to right lung end-tidal carbon dioxide tension difference. Fluid loading during collapse increased cardiac output and pulmonary vascular pressures, but .ovrhdot.Qs/.ovrhdot.Qt did not differ significantly from the normovolaemic collapsed state. Increasing the right mean airway pressure in this condition had no effect on .ovrhdot.Qs/.ovrhdot.Qt or carbon dioxide tensions.