2014B04 Describe an active anaesthetic gas scavenging system.



·      Diagramme

·      What is it, where is it, how does it work

·      Pros and cons




·  System for active removal of excess gas from anaesthetic circuit


·  ↓Volatile pollution

o ? Teratogenic

o Max recommended ~2ppm if alone, 0.5ppm if with N2O (USA)

·  ↓N2O pollution

o Oxidises Cobalt atom in Vit B12, a cofactor for methionine synthetase

o ↓DNA synthesis, bone marrow suppression, teratogenesis

o Max recommended 25ppm with or without volatile (USA)


·  In expiratory limb before CO2 absorber (spares it), attached to APL and APL bypass valves

·  Exhaust vent above ground, away from people


·  (Mostly) open system, cf. passive scavenging mostly closed

·  30mm tubing incompatible with breathing circuit, prevent accidental connection

·  High flow rate >100L/min, small neg pressure -0.5cmH2O

o (cf. medical suction: low flow rate, large neg pressure)


·  Effective across wide FGF range

·  Prevent operating room pollution


·  Requires power

·  Expensive

·  ↑↑ FGF rate -> leak into operating room

·  Blocked entrainment ports -> negative pressure APO

·  Atmospheric pollution




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