Distilled water

[palerider]

Does going dry shorten the lifespan of a CPAP machine? I’ve only occasionally used water.

How could it?

[D.H.]

Does going dry shorten the lifespan of a CPAP machine? I’ve only occasionally used water.

No, provided that you turn the humidifier off (or to zero).

[AusMatt]

You can use distilled water in whatever container you like. I used a small 16 fluid ounce bottle that previously held bottled water and put a label on the side saying: "Medically required CPAP distilled water". Depending on your airline, you may need to notify them to arrange for the use of an airline medical power outlet (these aren't disrupted as much as the seat power outlets). I've successfully used a ResMed Airsense 10 in flight.

The current TSA guideline page (retrieved 19 November 2023) that covers this is here: https://www.tsa.gov/travel/special-procedures.
It's now called "Disabilities and Medical Conditions" and has a drop down menu where you can choose "Respiratory Equipment". This reads:

Nebulizers, CPAPs, BiPAPs, and APAPs
A nebulizer, CPAP, BiPAP and APAP must be removed from its carrying case and undergo X-ray screening. Facemasks and tubing may remain in the case.
You may provide a clear plastic bag to place the device through the X-ray. A TSA officer may need to remove it from the bag to test it for traces of explosives.
Liquids associated with the nebulizer are exempt from the 3-1-1 liquids rule. Read about medication screening.

Note that I bolded the sentence: Liquids associated with the nebulizer are exempt from the 3-1-1 liquids rule.