CARBON DIOXIDE ELIMINATION DURING INSUFFLATION ANAESTHESIA

Carbon dioxide elimination during apnoea was measured in sixty patients undergoing diagnostic bronchoscopy. Paralysis was maintained using suxamethonium after thiopentone induction of anaesthesia. In forty patients a 50 per cent mixture of nitrous oxide and oxygen was insufflated by nylon catheter in the trachea at a rate of 10 l./min. The mean quantity of carbon dioxide eliminated was approximately 20 ml/min (range 0–0.8 per cent). In twenty patients without insufflation the corresponding rate was approximately 6 ml/min (range 0–0.25 per cent). The relationship of this finding to the known effect of the heartbeat in producing a small amount of alveolar ventilation is discussed.