Most newer CPAP machines do not run directly on 12VDC, but run on a “brick” or voltage converter, “transformer” of some sort. The 2 most common CPAP machine suppliers are ResMed and Respironics. The common voltages, though they both, (and all others too, as far as I know) run off a 110VAC plug into the wall at home, and convert the operating voltage to the manufactures specs. ResMed is 18 VDC, Respironices is 12 – 14 VDC. They have to convert the running voltage for the machine through a transformer that starts by running on 110VAC (standard home wall plug.)
Some things to know about CPAP machines.
1. There is CPAP = Continuous Positive Air Pressure (runs at a steady, set pressure) and,
2. There is a different type, APAP or Auto (adjustable) or Variable Positive Airway Pressure.
3. The Positive Air Pressure delivered is in cm of water pressure, (cmH2O) and
4. Has no relation to the humidity level or heater setting for the water chamber.
5. The heater setting determines the humidity level of the air that you will be breathing.
6. The warmer the temperature setting, the higher the humidity and, (in most cases generally), the more comfortable for the device wearer.
Now the kicker, AND you knew this was coming:
Running a heater uses electricity and that takes battery power. The heater on most units is adjustable from low to high and on some you can turn it off completely. Running the CPAP with the heater on will use more battery than with it off. Running it with the heat turned up will use more than with it turned down to low, or off. This allows you to use water, although it will be cold, and depending on the ambient temperature, there will still be some added humidity in the inhaled air. Yes, it will be cool to cold, depending on the flow, pressure and ambient temp. But it is still more humid than with no water at all.
7. With the temperature setting or heat setting at “OFF” there is no battery power used for heating so
8. You have more power to assign just to the PAP (Positive Airway Pressure) device.
9. With regard to the heated humidity use. IF you have a heated hose, you will also need to set it to manual / and,or turn the hose heater to off.
If you have a machine that will run on straight 12VDC, you will be better off as far as power consumption goes. Having to run either through a transformer or inverter means there is going to be an effective loss of power. If you have a device that will plug directly into the 12VDC Cig Plug, and does not power a heater or humidifier, you will be using the least amount of power possible and still be able to have the proper CPAP levels to be therapeutic.
Some things to consider: Do you need the humidity? Can you get by on a lower pressure? (That depends on your AHI score and Apnea diagnosis.) What manufacturer's machine do you have? and Is there any chance you might use a second machine, just for travel?
I hope this is some help. If you have any more questions, be sure and ask, and I'm glad to help.
There are several newer “Travel CPAP” units available. Some have 12VDC (Cig lighter) plugs, and those that do will have Cig lighter plugs available. Some have proprietary batteries that will power them. When using battery powered units, the useful battery run time will vary depending on the prescribed CPAP pressures required. Legitimate providers of this equipment will require a prescription even if the device in not being paid for by insurance. Medicare will cover 80% of the cost for the first (primary) machine with replacement in the 6th year of adequate therapeutic use. Most likely, if you are looking for a second device it will be on your “dime”.
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Harvey
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