Inspiratory to end-tidal oxygen difference during nitrous oxide anaesthesia.
In order to evaluate the value of the inspiratory to end-tidal oxygen concentration difference (Io2-E'o2) as a monitor during general anaesthesia, we studied 40 orthopaedic patients allocated randomly to four groups: anaesthesia with enflurane or isoflurane in nitrous oxide with either spontaneous or controlled ventilation. (Io2-E'o2) followed an asymptotically increasing curve because of decreasing uptake of nitrous oxide. At 1 h, (Io2-E'o2) approached the end-tidal carbon dioxide concentration (E'o2). During spontaneous ventilation, (Io2-E'o2) correlated best with E'co2. During controlled ventilation, there was a negative correlation between (Io2-E'o2) and nitrous oxide uptake rate. Changes in oxygen uptake rate were reflected in (Io2-E'o2), provided that the total ventilation volume was constant and the nitrous oxide uptake rate approached steady state conditions.
Bengtson
J P
JP
Department of Anaesthesia and Intensive Care, Sahlgren Hospital, University of Göteborg, Sweden.
Haraldsson
A
A
Bengtsson
A
A
Henriksson
B A
BA
Stenqvist
O
O
D000328:Adult; D000769:Anesthesia, Inhalation; D005260:Female; D006801:Humans; D008297:Male; D009609:Nitrous Oxide; D010100:Oxygen / Q000502:physiology*; D012119:Respiration / Q000502:physiology*; D012121:Respiration, Artificial; D013990:Tidal Volume / Q000502:physiology; D013997:Time Factors
D009609:Nitrous Oxide; D010100:Oxygen