I’ve included some photos of a disposable Non-Rebreather (NRB) Oxygen Mask, Clustermasx and M-size O2 cylinder with click style constant flow regulator, a Clustermasx configured with a mouth tube, a Western Medica flowmeter type constant flow O2 regulator with a CGA-540 Nut & Nipple fitting for use with the larger (M/H/K) oxygen cylinders, and an adapter that will let you use the same CGA-870 Yoke type constant flow O2 regulator on both E and M-size O2 cylinders.
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NRB O2 Mask – Thomas gave you a good link where you can order these.You’ll note arrows pointing to the two exhaust flapper valves in the photo above. Both of these silicone rubber flapper valves must be present or room air will enter the mask and the oxygen inhaled will be diluted to the point it will not work as an abortive to stop the pain of a cluster headache attack.
If possible, place the order by phone and ask for two. Make sure you tell them to ensure both exhaust flapper valves are present before you agree to buy them. They come in a clear plastic bag so if you buy two locally, inspect them carefully for the presence of both valves before you accept them. Most NRB O2 masks come from the factory missing at least one and sometimes both of the flapper valves. If you can get two, there’s a good chance you’ll have a total of two flapper valves to configure one NRB mask correctly.
As a safety note, make sure you remove the green elastic strap from the NRB O2 mask. All masks used for oxygen therapy to abort cluster headache attacks should be held in place by hand. It’s very easy to fall asleep after aborting a painful attack. If the mask fits tightly and both flapper valves are functioning properly with the mask held in place by the elastic strap, you could run out of O2 and that would not be good… That is also why many suppliers of this mask ship it missing at least one valve.
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Clustermasx – Mouth Tube ConfigurationMasks like these are hard to find here in the US but they are available over the internet. They cost more ($25 - $30 USD) but are reusable and provide a much better fit. They come in a kit with a mask and other spare parts like reservoir bags and valves.
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Clustermasx – Face Mask ConfigurationThis photo also shows a Click type constant flow regulator attached to an M-size O2 cylinder. If you have more than four attacks a day/night, you’re better off ordering the larger M-size O2 cylinder. I was going through an E-size O2 cylinder every day using a 25 LPM O2 regulator. The M-size cylinder lasted more than a week at 15 to 25 LPM using a CGA-540 flowmeter type constant flow O2 regulator like the one shown below.
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Flowmeter Type Constant Flow O2 Regulator (Western Medica)I’ve used one of these regulators with a Clustermasx for almost two years and they both work great. You adjust the flow rate with the needle valve at the base of the sight gage. It will deliver O2 flow rates well above 15 LPM by opening the needle valve to the “Flood Mode.”
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CGA-540 to CGA-870 Post Valve AdapterMultimedia File Viewing and Clickable Links are available for Registered Members only!! You need to

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CGA-540 to CGA-870 Post Valve Adapter on M-size O2 CylinderThis is a very handy adapter to have in your oxygen therapy kit. With one of these adapters you can use the same CGA-870 Yoke type constant flow O2 regulator (shown below) on the smaller E-size O2 cylinders while on travel and also at home on the larger (M/H/K) size O2 cylinders. You can find one of the CGA-540 to CGA-870 Post Valve Adapters at the following URL:
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CGA-870 “Yoke type” 0-25 LPM Constant Flow O2 RegulatorA 25 LPM regulator like this cut my abort times dramatically while I was using my E-size O2 cylinders away from home.