Anaesthesia system with eliminated spill valve adjustment and without lung rupture risk.
A new anaesthesia system is presented. Apart from the inclusion of an inflating valve which is influenced by bag compression, the components are those commonly used in any absorption circuit, but arranged in a new sequence. The anaesthesia system is characterized by its use of a spill valve with a fixed low opening pressure, thus eliminating the commonly haphazard adjustment of this valve. The magnitude of the fresh gas flow does not influence the pressure in the bag during its compression, thereby introducing the "closed system" bag feeling, otherwise excluded with semi-closed and high flow systems. For the same reason, dangerous pressures cannot arise in the lung, as its peak pressure is defined by the volume inflated from the bag, and is controllable by the anaesthetist. Dumping of expired air in preference to fresh gas makes gas expenses optimally low with any semi-closed inflow. The permanent low pressure inside the carbon dioxide absorber makes it easier to produce a tightly closed system and also makes more economical use of expensive gases. Disclosure of disconnection by a steadily rotating volumeter pointer may add to safety, the same feature apparently also being helpful in teaching proper mask technique.