Scavenging & suction · Kenrick Turner

# Scavenging & suction

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# Anaesthetic gas scavenging system (AGSS)

Reduce environmental anaesthetic gas concentrations by collecting waste gases and venting outside the building.

Arbitrary UK legal limits: N2O ≤ 100ppm; Isoflurane ≤ 50 ppm

Components:
1. Collection
2. Transfer
3. Receiving
4. Disposal

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# 1. Collection system

Connects to APL valve outlet or scavenging connector on anaesthetic machine

**30mm connector** to avoid accidental cross-connection with breathing system

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# 2. Transfer system

Corrugated plastic hose connecting collection and receiving systems

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# 3. Receiving system

## Open (active)

Reservoir with mesh-covered opening: allows compensation for variations in expiratory flow without generating positive/negative pressures.

## Closed (passive)

Length of tubing with positive (+5 cmH2O) and negative (-0.5 cmH2O) pressure relief valves.

Reservoir bag accommodates small changes in pressure without requiring valve opening.

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## Open receiving

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## Closed receiving

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# 4. Disposal

- Active:
 - Vacuum system
 - High flow (>100 L/min), low-pressure
- Passive:
 - "Hole in the wall"
 - Tubing directly vented to the atmosphere

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# Considerations

Scavenging does not prevent environmental pollution

Theatre ventilation systems further reduce ambient anaesthetic gas concentrations

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# Medical vacuum & suction

High pressure, low flow system: –53 kPa (–400 mmHg) with 40 L/min flow

Types:
- Wall suction outlets from central vacuum plant
- Portable units (e.g. Laerdal)

One vacuum outlet in anaesthetic room; two in theatre (one dedicated for anaesthetic use)

Described in **gauge pressure** (relative to atmospheric pressure) therefore cannot exceed –101 kPa

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# Central medical vacuum system