Pulmonary ventilation by continuous flow using a modified Carlenʼs tube

Abstract

Carlen's tubes were modified by introducing a manometer line into each lumen to allow both bronchi to be insufflated continuously. During such continuousflow ventilation (CFV) with a gas flow of 1 L/kg body weight min in 6 anesthetized dogs, both CO₂ and O₂ homeostasis were maintained. By contrast, during apneic oxygenation the mean Paco₂ rose by approximately 6 torr/min. After 12 min of apneic oxygenation the introduction of CFV at 1 L/kg min reduced the mean Paco₂ from 120 to 38 torr within 6 to 9 min; by 15 to 30 min the Paco₂ was stable at 33 torr. The mean Pao₂ was stable at 80 torr and 451 torr using air and oxygen, respectively, as the insufflating gas. When the CFV was reduced to 0.75 L/kg ± min, there was a rise in mean Paco₂ from 34 to 53 torr in 12 min; Paco₂ was then reduced to 40 torr when 4 breath/min was introduced with a mean tidal volume of 375 ml.