Oxygenation during Anaesthesia with Controlled Ventilation

There is an increased alveolar-arterial oxygen tension difference (A-a Po2) and venous admixture effect during anaesthesia with thiopentone, nitrous oxide and oxygen with pethidine and controlled ventilation. This percentage venous admixture is reduced when large tidal volumes are used for ventilation. It is recommended that the inspired oxygen concentration should be kept above 30 per cent and that the venous admixture effect should be minimized by the use of large tidal volumes.