This page will collate information relevant for institutions considering decommissioning of nitrous oxide pipelines. It will include strategies for cylinder provision and process for decommissioning.
UK and Ireland Anaesthesia bodies have recommended nitrous pipelines be decommissioned and cylinders used in lieu. AusHFG and NSW guidelines no longer recommend reticulated nitrous oxide for all new facilities. So how to go about decommissioning your likely leaky nitrous pipes? A proposed phased approach outlined below.
Phase 1 – Cut off dead wood
Disconnect and decommission nitrous pipeline from all areas which do not use nitrous oxide. Examples may include outpatients, emergency departments, radiology areas and areas connected for historical reasons. Portable entonox cylinders can be available for use in clinical areas
Removing unused limbs of the pipeline is important. Every metre of pipeline removed is a metre less that can leak
Keep pipeline active for operating theatres with children and birthsuites
Phase 2 – Cylinders for theatres
Stop using pipelines for operating theatre nitrous oxide. Provide N2O cylinders, with regulator either connected directly to anaesthetic machine, or available to be brought in on a trolley and connected to nitrous oxide gas hose when required.
Keep pipeline active only for birthsuites. Maintain theatre pipeline to provide reassurance to staff until trial complete.
Phase 3 – Cylinders for all
The birthsuite can be supplied by local entonox cylinders which are mobile, allowing better access to N2O in shower or areas of room. Nitrous oxide pipeline can be decommissioned.
It may be that a well maintained small manifold system for a birthsuite is easy to maintain, test and keep leak proof, depending on your facility resources.
Do you have a better way of phasing out your leaky nitrous pipelines? Let us know!
N2O Cylinder Provision: Anaesthesia
Possible strategies to provide nitrous oxide cylinders for anaesthesia are as follows
- For Anaesthesia Consultants who require nitrous oxide for every case (minority) – provide a cylinder in theatre whenever that consultant is working. This may require several N2O D-sized cylinders per theatre complex, which can be connected via the pipeline nitrous hosing. Need a regulator to drop cylinder pressure 400kpa.
- For Consultants who can predict their likely need for nitrous oxide (eg: paeds gas inductions) provide D size nitrous oxide cylinder in theatre on request (with 400kpa regulator)
- For theatres with regular paediatric gas inductions – have a C-size cylinder bolted to the rear of the machine, next to the oxygen backup cylinder. Most machines have capacity to have at least 2 cylinders secured to the rear of the machine (one oxygen and one nitrous oxide). Some machines allow 3 cylinders.
| Brand | Model | Nitrous Oxide Cylinder Options | Reference |
| Drager | Perseus | C or D size nitrous oxide cylinder | Personal communication NSW Health |
| Drager | Zeus | Zeus does have capacity for nitrous backup cylinder connection along with air and O2 (see p23 IFU). A backup air cylinder should remain since the DIVA and sometimes suction are driven by air supply. Only space for 2 cylinders at a time though. If maintaining air and oxygen cylinders, a nitrous Oxide cylinder would have to connect via pipeline hose unless a harness can be developed to hold the 3rd cylinder (n2O) | Zeus IE IFU |
| GE | Aisys CS2 | Up to 3 cylinder connections (although space may be an issue?) C cylinder nitrous oxide. | Aisys IFU |
| GE | Carestation 620 / 650 (not 650c) | 2 cylinder connections, 3rd optional for ‘outboard’ cylinder. C cylinder nitrous oxide. Large cylinders (O2/N2O) optional. | Carestation IFU |
| Drager | Fabius | 2 cylinders – O2 and N2O | Observation FSH |
How to set up a portable nitrous oxide cylinder for theatres
The mini-manifold: 2 x C cylinders with a switch to quickly switch over between cylinders when one runs out
The swap-it when it’s low approach: Have a C or D sized cylinder which is swapped out at an agreed pressure.
When should a nitrous cylinder be replaced, in theatre?
It depends on the cylinder and how it is connected to the anaesthetic machine
A medical C cylinder has a water volume of 2.9l, 1.75 kg N2O =935 L at 1 atm.
With the function pressure of a cylinder being 4,600-5,200kPa, when connected via a yoke, a low pressure occurs alarm at 2633kPa, which correlates to about 70L remaining in an Australian C cylinder. This should give ample warning (280 minutes at 250ml N2O per min, or 14 minutes at 5 L N2O per min), and allow a cylinder change.
If a D cylinder is connected via a regulator and pipeline hose the first audible alarm will occur when the low N2O pressure alarm is reached at 254kPa (GE manual). At this threshold, there is approximately 25L of N2O in a D cylinder, providing enough warning to allow for a cylinder change.
Engineers Perspective – Decommissioning a pipeline
We asked a hospital engineer recently involved in decommissioning a nitrous oxide pipeline to summarise the steps – here they are.
- Letter from the Hospital confirming their approval to decommission the Nitrous Oxide
- Undertake an audit of the current setup – Review the drawings and confirm on site for:
- Nitrous oxide outlets – location and quantity
- Routing of piping and location of isolations – for each building and if large building, if isolation for different floors.
- Locate all Medical gas alarm panels, the model. For some older system (as we had in our theatres were local with pressure switches and LEDs)
Decommissioning
- Isolate building.
- Critical step – shunt Nitrous Oxide alarm on the medical gas panels in the building and or pressure switch if mercury type with LED (old system)
- Vent the outlets.
- Plug with specially made plugs (we got ours made by in SS steel)
- Add labels to all medical gas panels and all outlets plugged
- Repeat to all buildings
- Then disconnect main supply isolate and plug
- Insert Label – Nitrous Oxide Decommissioned
Resources
Decommissioning N2O Playbook – USA Cascadia Collaborative
Guide to Decommissioning Nitrous Oxide Pipelines – United Kingdom NHS, UCL