[A clinical study of co2-elimination using a modified bain-system (author's transl)]

Of three groups of anaesthetized and intubated patients (n = 7) under controlled ventilation two received fresh gas flows of 70 ml/kg . min, 100 ml/kg . min and 130 ml/kg . min either in increasing or in decreasing amounts via a Bain circuit, while the third group was ventilated via a conventional semi-closed anaesthesia circuit. Blood gas analyses and cardiovascular parameters were recorded. In one patient temperatures and relative humidities of in- and expired gases were obtained by psychrometry. A modification of the Bain system afforded control of respiratory minute volumes and airway pressures. CO2-elimination proved to be adequate at a fresh gas flow of 130 ml/kg. min. At 100 ml/kg. min it was acceptable still, however pH values were outside normal range. With 70 ml/kg . min mean capillary pCO2 values (42.6 mmHg and 43.2 mmHg) and mean pH values (7.32 and 7.33) in the two respective groups proved a respiratory acidosis. Capillary pO2 was above 100 mmHg in all groups. Temperature and relative humidity of inspired gases were 24 degrees C and 40 per cent, 23 degrees C and 25 per cent, 22 degrees C and 3 per cent at fresh gas flows of 70, 100 and 130 ml/kg . min respectively.