HOW TO HEAT YOUR CPAP AIR

By Bernard Morey
Melbourne, Australia

If you're on CPAP you're often on it for life.  It's great in summer but winter means a wet lip or, worse, a nostril full of condensation several times a night.  Unless, that is, you want to wake up half a dozen times a night and mop out your mask with a tissue, which rather defeats the purpose of going on to CPAP in the first place.

Insulated hoses just don't cut it.  The solution is a heated hose or heated air.  There is a heated hose available on mail order from Australia — but it costs $157 plus postage.

There are two suggestions. The first duplicates the commercial heated hose. The second (below) uses a heated manifold.

Heating the Hose

Oatley Electronics (Sydney, Australia) have a new 15w general purpose heater kit, advertised as being for pets and brewers. This cost is AUD $25 plus postage.  This looked as if it could be readily adapted to a CPAP hose. It can if you don't mind a bit of fiddling on the kitchen bench.  I've ironed out most of the wrinkles, so here's the inside story of how to make your own hose. 

Actually, you don't need the Oatley kit as the parts are easily available where you are as long as you have an electrical wholesaler and an electronics store similar to Tandy nearby (Australia: Jaycar, Altronics, Radio Parts, Dick Smith).

The system works on low voltage so it is safe to make and use.

I have tested this heater in Melbourne, Australia, and it works very well.  Melbourne, however, has a milder climate than northern USA and the UK.  This heater radiates 15 watts. More heat may be needed in a colder climate or if you use a heated humidifier.  On the other hand too much heat will dry out your nostrils.  An adjustable heater would be better but that's beyond my expertise.  The construction is simple and it could be made to run hotter without much extra work, if needed.

If someone had a commercial heated hose and could supply the electrical parameters it would be simple to adapt this design to match.

If you have any trouble feel free to email me.

Equipment

Item Comments
Overlocker To make the sock. A sewing machine will do just as well.
Crimpers To join wires. Small wire joiners will do.
Pliers Needle nose variety. Not essential but useful
Wire stripper Not essential. A carton knife will do. Watch fingers!
Vice To hold things while you work on them. You can do without it.
Side-cutters To trim the cable ties. Or use pliers.

Parts

Item Comments
7 metres underfloor heating cable See photogallery. I first tried using nichrome but its
resistance is too high. I also tried stripping an electric
blanket and using the wire from that, but the resistance
is still too high for 9 volts.
4 x wire butt joiners Used with the crimper. Spade joiners will do.
Transformer — local mains voltage
to 9 volts AC at 2 amps		 12 volts will work but you'll have to recalculate
 the length of wire required.
Hook-up wire, insulated Speaker wire or twinflex is fine. As much has you
need to go from your hose to a power point.
Cable ties For securing wires to the hose
Polar fleece fabric (or similar) To make the sock.

Photogallery

Click on photo for the full-size picture.

Heating cable, sub-floor type

This cable is double-insulated, 7mm thick and stiff. All we need is the wire core, no insulation. As we are using low voltage this is fine. Strip the insulation off by exposing a bit of wire, clamping it in a vice, then pulling off the insulation one layer at a time. It is hard work and the stripped wire tends to tangle.

Heating cable - label

The resistance of this cable is 0.7 ohms per metre.

Cutting out the tube

Made from polar fleece, from a fabric shop. It's real cheap. You'll probably have to join two lengths to fit a 1.8 metre hose.

Overlocking the tube.

Sewing will do just as well. After this, turn the tube inside-out. My wife had a thingy for doing this. Otherwise it's tricky.

Transformer

Transformer

This has an Australian plug. Your transformer will have the correct plug for where you buy it.

Transformer - label

This is an Australian 240v version. UK wil be 220V, US 110v, &c. Output is 9 volts AC. A DC transformer will do but will be more expensive and serve no extra purpose.

Winding the stripped heating wire

My wife helped. The start of the wire is held in place with a cable tie. The tube is supported on a piece of towel rail but this is not necessary. Holding it in your hand is just as easy. Wind it fairly tight but not tight enough to wrinkle the tube.

Connections

After winding the heating wire and securing it at both ends, connect the hookup wire using suitable connectors and hold in place with cable ties. Trim ties. NOTE: 7 metres of wire covers just over half the tube.

Connections - other end

After this I secured the hook-up wire at the midpoints with cable ties and also at the far end, which will be the blower end of the tube.

Room temperature.

Time to test what's happening when it's wired to the transformer and connected to the mains. Room temperature is cool but not cold.

Testing

You probably won't feel much, if any, heat from the tube. 15 watts over approx. 700mm is not much heat over a handswidth. This is the temperate in the tube without the blower on. Nothing more than a warm summer's day for those of you still using antique Imperial measures.

Temperature with blower on

Just nice - an airconditioned office. This is with no backpressure from the mask and your breathing. Working temperature will obviously be somewhere between this and the static temperature.

Finished project.

I should have made the hookup wire longer but this was all I had in my odds-and-ends-bucket.

Installed

... on my Remstar Pro ready for a good night's sleep -- at last!

Calculator

Useful for working out output in watts from different inputs and resistances.

Heating the Air

Another possibility. This is untried but I can’t see why it wouldn’t work. It also has the advantage of providing adjustable heat. If anyone tries it let me know.

The Concept

Air passing through a heated manifold is warmed to a comfortable temperature.

Construction

Measure the height of a 150 watt incandescent globe in a standard batten-fix holder. Purchase a wooden box of this height (with lid) plus, say, 25mm. These boxes are available in craft and hobby suppliers. They are used a base for decorative painting and are cheap. Drill holes so the lid can be screwed on to provide an air-tight seal.

Drill two holes in each side and fit/glue a small length of PVC pipe (from a hardware or plumbing shop) of a diameter that will fit a CPAP hose (internally or externally).

Fit lamp holder and a dimmer/switch to suit. Wire up with a length of standard mains voltage light duty 2-core cable and suitable plug. Save the cord off a discarded appliance and use that! Seal wiring holes and pipes (silicon will do). Insulate ‘out’ tube with sock as previously described.

Temperature is adjustable using the dimmer. Great for seasonal changes or variable nights.

If game ask wife to decorate box (see here for example). This is the type of box, only taller. Install another lamp and shade on top and it doubles as bedside lamp!

Safety

Suggest fit fine mesh or other filter over the ‘out’ tube so in the unlikely event the lamp shatters fine glass is not blown down the tube. The chances of this are minute but it’s a simple addition.

Arrange inlet/outlet PVC tubes so any water coming down the tube cannot drip on the globe.

Do not run lamp without air on.