Effects of altered patterns of ventilation and of increased cardiac output on blood flow to a collapsed lung in anaesthetized, closed-chest dogs.
Right-to-left shunt (Qs/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 Qs/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 Qs/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 Qs/Qt did not differ significantly from the normovolaemic collapsed state. Increasing the right mean airway pressure in this condition had no effect on Qs/Qt or carbon dioxide tensions.
Niblett
D J
DJ
Nuffield Department of Anaesthetics, Radcliffe Infirmary, Oxford.
Cannon
D
D
Sykes
M K
MK
D000771:Anesthesia, Intravenous; D000818:Animals; D002302:Cardiac Output; D004285:Dogs; D011175:Positive-Pressure Respiration; D001261:Pulmonary Atelectasis / Q000503:physiopathology*; D011652:Pulmonary Circulation; D012119:Respiration