Effects of nitrous oxide on respiration during halothane anaesthesia in the dog.

The pattern of ventilation was studied in eight greyhounds anaesthetized with halothane in 50% oxygen with nitrogen and in eight with the same concentration of halothane in 50% oxygen with nitrous oxide. There was a significant reduction in both inspiratory and expiratory times in the animals breathing nitrous oxide and an increase in the negative pressures developed in the obstructed airway during inspiration. Measurements during the addition of carbon dioxide to the inspired gases also suggested less respiratory depression in the nitrous oxide breathing group. It was concluded that nitrous oxide may counteract the respiratory depressant effects of halothane.