2014B04 Describe an active anaesthetic gas scavenging system.

Diagramme

Definition

·  System for active removal of excess gas from anaesthetic circuit

Purpose

·  ↓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)

Location

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

·  Exhaust vent above ground, away from people

Mechanics

·  (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)

Pros

·  Effective across wide FGF range

·  Prevent operating room pollution

Cons

·  Requires power

·  Expensive

·  ↑↑ FGF rate -> leak into operating room

·  Blocked entrainment ports -> negative pressure APO

·  Atmospheric pollution