A new ResMed ClimateLine headed CPAP hose arrived on schedule and let me measure the old hose:
The center two they-are-not-USB contacts on the input end of the hose (on the right) are for to the heating element spiraling around the tube and measure 10.0 Ω.
The outer two contacts report back from what must be a 10 kΩ thermistor embedded in the dingus sticking into the hose lumen at the output end (on the left). It reads 12 kΩ in a 68 °F room and responds to warmth with a lower resistance, which is what you’d expect.
Plugging the ClimateLine hose into the AirSense 11 unit enables temperature sensing at the end of the hose, with closed loop control from 60 °F to 86 °F. Mary set it to 80 °F in manual mode, which apparently produces different results from the same temperature in Auto mode, and declared victory.
A humidity setting of 4, in the middle of the 1 – 8 range, works for her.
Both the AirSense 11 and its power brick claim 24 VDC at a suspiciously exact 2.71 A. The hose heater could soak up 2.4 A of that, but the AirSense 11 also heats the humidifier’s water tank (“tub”), so it’s unlikely they’re both seeing the full 24 V.
I am prohibited from further investigation. [grin]
The Smell of Molten Projects in the Morning 
Hi there! This may be borderline off-topic but do you know if the piece of plastic protruding into the center of the output end of the hose has any functional purpose? Does it have sensors for air flow and/or temperature or is it to prevent users from being able to insert a tubing brush to clean it? I’d like to remove it so I can use a tubing brush. Thanks!
I’m pretty sure that’s where the themistor lives: breaking it off would be an expensive mistake.
We run a loooong tubing brush in from the other end and ignore the six inches it can’t quite reach. It may be possible to compress the tubing by half a foot to get the brush where it should go, but the event is already enough of a wrestling match.